FCL/sf/os/persistentdata: comparison persistentstorage/sqlite3api/SQLite/select.c

equal deleted inserted replaced

--1:000000000000
+:08ec8eefde2f
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains C code routines that are called by the parser
+** to handle SELECT statements in SQLite.
+**
+** $Id: select.c,v 1.476 2008/09/23 09:36:10 drh Exp $
+*/
+#include "sqliteInt.h"
+/*
+** Delete all the content of a Select structure but do not deallocate
+** the select structure itself.
+*/
+static void clearSelect(sqlite3 *db, Select *p){
+sqlite3ExprListDelete(db, p->pEList);
+sqlite3SrcListDelete(db, p->pSrc);
+sqlite3ExprDelete(db, p->pWhere);
+sqlite3ExprListDelete(db, p->pGroupBy);
+sqlite3ExprDelete(db, p->pHaving);
+sqlite3ExprListDelete(db, p->pOrderBy);
+sqlite3SelectDelete(db, p->pPrior);
+sqlite3ExprDelete(db, p->pLimit);
+sqlite3ExprDelete(db, p->pOffset);
+}
+/*
+** Initialize a SelectDest structure.
+*/
+void sqlite3SelectDestInit(SelectDest *pDest, int eDest, int iParm){
+pDest->eDest = eDest;
+pDest->iParm = iParm;
+pDest->affinity = 0;
+pDest->iMem = 0;
+pDest->nMem = 0;
+}
+/*
+** Allocate a new Select structure and return a pointer to that
+** structure.
+*/
+Select *sqlite3SelectNew(
+Parse *pParse,        /* Parsing context */
+ExprList *pEList,     /* which columns to include in the result */
+SrcList *pSrc,        /* the FROM clause -- which tables to scan */
+Expr *pWhere,         /* the WHERE clause */
+ExprList *pGroupBy,   /* the GROUP BY clause */
+Expr *pHaving,        /* the HAVING clause */
+ExprList *pOrderBy,   /* the ORDER BY clause */
+int isDistinct,       /* true if the DISTINCT keyword is present */
+Expr *pLimit,         /* LIMIT value.  NULL means not used */
+Expr *pOffset         /* OFFSET value.  NULL means no offset */
+){
+Select *pNew;
+Select standin;
+sqlite3 *db = pParse->db;
+pNew = sqlite3DbMallocZero(db, sizeof(*pNew) );
+assert( !pOffset || pLimit );   /* Can't have OFFSET without LIMIT. */
+if( pNew==0 ){
+pNew = &standin;
+memset(pNew, 0, sizeof(*pNew));
+}
+if( pEList==0 ){
+pEList = sqlite3ExprListAppend(pParse, 0, sqlite3Expr(db,TK_ALL,0,0,0), 0);
+}
+pNew->pEList = pEList;
+pNew->pSrc = pSrc;
+pNew->pWhere = pWhere;
+pNew->pGroupBy = pGroupBy;
+pNew->pHaving = pHaving;
+pNew->pOrderBy = pOrderBy;
+pNew->selFlags = isDistinct ? SF_Distinct : 0;
+pNew->op = TK_SELECT;
+assert( pOffset==0 || pLimit!=0 );
+pNew->pLimit = pLimit;
+pNew->pOffset = pOffset;
+pNew->addrOpenEphm[0] = -1;
+pNew->addrOpenEphm[1] = -1;
+pNew->addrOpenEphm[2] = -1;
+if( db->mallocFailed ) {
+clearSelect(db, pNew);
+if( pNew!=&standin ) sqlite3DbFree(db, pNew);
+pNew = 0;
+}
+return pNew;
+}
+/*
+** Delete the given Select structure and all of its substructures.
+*/
+void sqlite3SelectDelete(sqlite3 *db, Select *p){
+if( p ){
+clearSelect(db, p);
+sqlite3DbFree(db, p);
+}
+}
+/*
+** Given 1 to 3 identifiers preceeding the JOIN keyword, determine the
+** type of join.  Return an integer constant that expresses that type
+** in terms of the following bit values:
+**
+**     JT_INNER
+**     JT_CROSS
+**     JT_OUTER
+**     JT_NATURAL
+**     JT_LEFT
+**     JT_RIGHT
+**
+** A full outer join is the combination of JT_LEFT and JT_RIGHT.
+**
+** If an illegal or unsupported join type is seen, then still return
+** a join type, but put an error in the pParse structure.
+*/
+int sqlite3JoinType(Parse *pParse, Token *pA, Token *pB, Token *pC){
+int jointype = 0;
+Token *apAll[3];
+Token *p;
+static const struct {
+const char zKeyword[8];
+u8 nChar;
+u8 code;
+} keywords[] = {
+{ "natural", 7, JT_NATURAL },
+{ "left",    4, JT_LEFT|JT_OUTER },
+{ "right",   5, JT_RIGHT|JT_OUTER },
+{ "full",    4, JT_LEFT|JT_RIGHT|JT_OUTER },
+{ "outer",   5, JT_OUTER },
+{ "inner",   5, JT_INNER },
+{ "cross",   5, JT_INNER|JT_CROSS },
+};
+int i, j;
+apAll[0] = pA;
+apAll[1] = pB;
+apAll[2] = pC;
+for(i=0; i<3 && apAll[i]; i++){
+p = apAll[i];
+for(j=0; j<sizeof(keywords)/sizeof(keywords[0]); j++){
+if( p->n==keywords[j].nChar
+&& sqlite3StrNICmp((char*)p->z, keywords[j].zKeyword, p->n)==0 ){
+jointype |= keywords[j].code;
+break;
+}
+}
+if( j>=sizeof(keywords)/sizeof(keywords[0]) ){
+jointype |= JT_ERROR;
+break;
+}
+}
+if(
+(jointype & (JT_INNER|JT_OUTER))==(JT_INNER|JT_OUTER) ||
+(jointype & JT_ERROR)!=0
+){
+const char *zSp = " ";
+assert( pB!=0 );
+if( pC==0 ){ zSp++; }
+sqlite3ErrorMsg(pParse, "unknown or unsupported join type: "
+"%T %T%s%T", pA, pB, zSp, pC);
+jointype = JT_INNER;
+}else if( jointype & JT_RIGHT ){
+sqlite3ErrorMsg(pParse,
+"RIGHT and FULL OUTER JOINs are not currently supported");
+jointype = JT_INNER;
+}
+return jointype;
+}
+/*
+** Return the index of a column in a table.  Return -1 if the column
+** is not contained in the table.
+*/
+static int columnIndex(Table *pTab, const char *zCol){
+int i;
+for(i=0; i<pTab->nCol; i++){
+if( sqlite3StrICmp(pTab->aCol[i].zName, zCol)==0 ) return i;
+}
+return -1;
+}
+/*
+** Set the value of a token to a '\000'-terminated string.
+*/
+static void setToken(Token *p, const char *z){
+p->z = (u8*)z;
+p->n = z ? strlen(z) : 0;
+p->dyn = 0;
+}
+/*
+** Set the token to the double-quoted and escaped version of the string pointed
+** to by z. For example;
+**
+**    {a"bc}  ->  {"a""bc"}
+*/
+static void setQuotedToken(Parse *pParse, Token *p, const char *z){
+/* Check if the string appears to be quoted using "..." or `...`
+** or [...] or '...' or if the string contains any " characters.
+** If it does, then record a version of the string with the special
+** characters escaped.
+*/
+const char *z2 = z;
+if( *z2!='[' && *z2!='`' && *z2!='\'' ){
+while( *z2 ){
+if( *z2=='"' ) break;
+z2++;
+}
+}
+if( *z2 ){
+/* String contains " characters - copy and quote the string. */
+p->z = (u8 *)sqlite3MPrintf(pParse->db, "\"%w\"", z);
+if( p->z ){
+p->n = strlen((char *)p->z);
+p->dyn = 1;
+}
+}else{
+/* String contains no " characters - copy the pointer. */
+p->z = (u8*)z;
+p->n = (z2 - z);
+p->dyn = 0;
+}
+}
+/*
+** Create an expression node for an identifier with the name of zName
+*/
+Expr *sqlite3CreateIdExpr(Parse *pParse, const char *zName){
+Token dummy;
+setToken(&dummy, zName);
+return sqlite3PExpr(pParse, TK_ID, 0, 0, &dummy);
+}
+/*
+** Add a term to the WHERE expression in *ppExpr that requires the
+** zCol column to be equal in the two tables pTab1 and pTab2.
+*/
+static void addWhereTerm(
+Parse *pParse,           /* Parsing context */
+const char *zCol,        /* Name of the column */
+const Table *pTab1,      /* First table */
+const char *zAlias1,     /* Alias for first table.  May be NULL */
+const Table *pTab2,      /* Second table */
+const char *zAlias2,     /* Alias for second table.  May be NULL */
+int iRightJoinTable,     /* VDBE cursor for the right table */
+Expr **ppExpr,           /* Add the equality term to this expression */
+int isOuterJoin          /* True if dealing with an OUTER join */
+){
+Expr *pE1a, *pE1b, *pE1c;
+Expr *pE2a, *pE2b, *pE2c;
+Expr *pE;
+pE1a = sqlite3CreateIdExpr(pParse, zCol);
+pE2a = sqlite3CreateIdExpr(pParse, zCol);
+if( zAlias1==0 ){
+zAlias1 = pTab1->zName;
+}
+pE1b = sqlite3CreateIdExpr(pParse, zAlias1);
+if( zAlias2==0 ){
+zAlias2 = pTab2->zName;
+}
+pE2b = sqlite3CreateIdExpr(pParse, zAlias2);
+pE1c = sqlite3PExpr(pParse, TK_DOT, pE1b, pE1a, 0);
+pE2c = sqlite3PExpr(pParse, TK_DOT, pE2b, pE2a, 0);
+pE = sqlite3PExpr(pParse, TK_EQ, pE1c, pE2c, 0);
+if( pE && isOuterJoin ){
+ExprSetProperty(pE, EP_FromJoin);
+pE->iRightJoinTable = iRightJoinTable;
+}
+*ppExpr = sqlite3ExprAnd(pParse->db,*ppExpr, pE);
+}
+/*
+** Set the EP_FromJoin property on all terms of the given expression.
+** And set the Expr.iRightJoinTable to iTable for every term in the
+** expression.
+**
+** The EP_FromJoin property is used on terms of an expression to tell
+** the LEFT OUTER JOIN processing logic that this term is part of the
+** join restriction specified in the ON or USING clause and not a part
+** of the more general WHERE clause.  These terms are moved over to the
+** WHERE clause during join processing but we need to remember that they
+** originated in the ON or USING clause.
+**
+** The Expr.iRightJoinTable tells the WHERE clause processing that the
+** expression depends on table iRightJoinTable even if that table is not
+** explicitly mentioned in the expression.  That information is needed
+** for cases like this:
+**
+**    SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.b AND t1.x=5
+**
+** The where clause needs to defer the handling of the t1.x=5
+** term until after the t2 loop of the join.  In that way, a
+** NULL t2 row will be inserted whenever t1.x!=5.  If we do not
+** defer the handling of t1.x=5, it will be processed immediately
+** after the t1 loop and rows with t1.x!=5 will never appear in
+** the output, which is incorrect.
+*/
+static void setJoinExpr(Expr *p, int iTable){
+while( p ){
+ExprSetProperty(p, EP_FromJoin);
+p->iRightJoinTable = iTable;
+setJoinExpr(p->pLeft, iTable);
+p = p->pRight;
+}
+}
+/*
+** This routine processes the join information for a SELECT statement.
+** ON and USING clauses are converted into extra terms of the WHERE clause.
+** NATURAL joins also create extra WHERE clause terms.
+**
+** The terms of a FROM clause are contained in the Select.pSrc structure.
+** The left most table is the first entry in Select.pSrc.  The right-most
+** table is the last entry.  The join operator is held in the entry to
+** the left.  Thus entry 0 contains the join operator for the join between
+** entries 0 and 1.  Any ON or USING clauses associated with the join are
+** also attached to the left entry.
+**
+** This routine returns the number of errors encountered.
+*/
+static int sqliteProcessJoin(Parse *pParse, Select *p){
+SrcList *pSrc;                  /* All tables in the FROM clause */
+int i, j;                       /* Loop counters */
+struct SrcList_item *pLeft;     /* Left table being joined */
+struct SrcList_item *pRight;    /* Right table being joined */
+pSrc = p->pSrc;
+pLeft = &pSrc->a[0];
+pRight = &pLeft[1];
+for(i=0; i<pSrc->nSrc-1; i++, pRight++, pLeft++){
+Table *pLeftTab = pLeft->pTab;
+Table *pRightTab = pRight->pTab;
+int isOuter;
+if( pLeftTab==0 || pRightTab==0 ) continue;
+isOuter = (pRight->jointype & JT_OUTER)!=0;
+/* When the NATURAL keyword is present, add WHERE clause terms for
+** every column that the two tables have in common.
+*/
+if( pRight->jointype & JT_NATURAL ){
+if( pRight->pOn || pRight->pUsing ){
+sqlite3ErrorMsg(pParse, "a NATURAL join may not have "
+"an ON or USING clause", 0);
+return 1;
+}
+for(j=0; j<pLeftTab->nCol; j++){
+char *zName = pLeftTab->aCol[j].zName;
+if( columnIndex(pRightTab, zName)>=0 ){
+addWhereTerm(pParse, zName, pLeftTab, pLeft->zAlias,
+pRightTab, pRight->zAlias,
+pRight->iCursor, &p->pWhere, isOuter);
+}
+}
+}
+/* Disallow both ON and USING clauses in the same join
+*/
+if( pRight->pOn && pRight->pUsing ){
+sqlite3ErrorMsg(pParse, "cannot have both ON and USING "
+"clauses in the same join");
+return 1;
+}
+/* Add the ON clause to the end of the WHERE clause, connected by
+** an AND operator.
+*/
+if( pRight->pOn ){
+if( isOuter ) setJoinExpr(pRight->pOn, pRight->iCursor);
+p->pWhere = sqlite3ExprAnd(pParse->db, p->pWhere, pRight->pOn);
+pRight->pOn = 0;
+}
+/* Create extra terms on the WHERE clause for each column named
+** in the USING clause.  Example: If the two tables to be joined are
+** A and B and the USING clause names X, Y, and Z, then add this
+** to the WHERE clause:    A.X=B.X AND A.Y=B.Y AND A.Z=B.Z
+** Report an error if any column mentioned in the USING clause is
+** not contained in both tables to be joined.
+*/
+if( pRight->pUsing ){
+IdList *pList = pRight->pUsing;
+for(j=0; j<pList->nId; j++){
+char *zName = pList->a[j].zName;
+if( columnIndex(pLeftTab, zName)<0 || columnIndex(pRightTab, zName)<0 ){
+sqlite3ErrorMsg(pParse, "cannot join using column %s - column "
+"not present in both tables", zName);
+return 1;
+}
+addWhereTerm(pParse, zName, pLeftTab, pLeft->zAlias,
+pRightTab, pRight->zAlias,
+pRight->iCursor, &p->pWhere, isOuter);
+}
+}
+}
+return 0;
+}
+/*
+** Insert code into "v" that will push the record on the top of the
+** stack into the sorter.
+*/
+static void pushOntoSorter(
+Parse *pParse,         /* Parser context */
+ExprList *pOrderBy,    /* The ORDER BY clause */
+Select *pSelect,       /* The whole SELECT statement */
+int regData            /* Register holding data to be sorted */
+){
+Vdbe *v = pParse->pVdbe;
+int nExpr = pOrderBy->nExpr;
+int regBase = sqlite3GetTempRange(pParse, nExpr+2);
+int regRecord = sqlite3GetTempReg(pParse);
+sqlite3ExprCodeExprList(pParse, pOrderBy, regBase, 0);
+sqlite3VdbeAddOp2(v, OP_Sequence, pOrderBy->iECursor, regBase+nExpr);
+sqlite3ExprCodeMove(pParse, regData, regBase+nExpr+1, 1);
+sqlite3VdbeAddOp3(v, OP_MakeRecord, regBase, nExpr + 2, regRecord);
+sqlite3VdbeAddOp2(v, OP_IdxInsert, pOrderBy->iECursor, regRecord);
+sqlite3ReleaseTempReg(pParse, regRecord);
+sqlite3ReleaseTempRange(pParse, regBase, nExpr+2);
+if( pSelect->iLimit ){
+int addr1, addr2;
+int iLimit;
+if( pSelect->iOffset ){
+iLimit = pSelect->iOffset+1;
+}else{
+iLimit = pSelect->iLimit;
+}
+addr1 = sqlite3VdbeAddOp1(v, OP_IfZero, iLimit);
+sqlite3VdbeAddOp2(v, OP_AddImm, iLimit, -1);
+addr2 = sqlite3VdbeAddOp0(v, OP_Goto);
+sqlite3VdbeJumpHere(v, addr1);
+sqlite3VdbeAddOp1(v, OP_Last, pOrderBy->iECursor);
+sqlite3VdbeAddOp1(v, OP_Delete, pOrderBy->iECursor);
+sqlite3VdbeJumpHere(v, addr2);
+pSelect->iLimit = 0;
+}
+}
+/*
+** Add code to implement the OFFSET
+*/
+static void codeOffset(
+Vdbe *v,          /* Generate code into this VM */
+Select *p,        /* The SELECT statement being coded */
+int iContinue     /* Jump here to skip the current record */
+){
+if( p->iOffset && iContinue!=0 ){
+int addr;
+sqlite3VdbeAddOp2(v, OP_AddImm, p->iOffset, -1);
+addr = sqlite3VdbeAddOp1(v, OP_IfNeg, p->iOffset);
+sqlite3VdbeAddOp2(v, OP_Goto, 0, iContinue);
+VdbeComment((v, "skip OFFSET records"));
+sqlite3VdbeJumpHere(v, addr);
+}
+}
+/*
+** Add code that will check to make sure the N registers starting at iMem
+** form a distinct entry.  iTab is a sorting index that holds previously
+** seen combinations of the N values.  A new entry is made in iTab
+** if the current N values are new.
+**
+** A jump to addrRepeat is made and the N+1 values are popped from the
+** stack if the top N elements are not distinct.
+*/
+static void codeDistinct(
+Parse *pParse,     /* Parsing and code generating context */
+int iTab,          /* A sorting index used to test for distinctness */
+int addrRepeat,    /* Jump to here if not distinct */
+int N,             /* Number of elements */
+int iMem           /* First element */
+){
+Vdbe *v;
+int r1;
+v = pParse->pVdbe;
+r1 = sqlite3GetTempReg(pParse);
+sqlite3VdbeAddOp3(v, OP_MakeRecord, iMem, N, r1);
+sqlite3VdbeAddOp3(v, OP_Found, iTab, addrRepeat, r1);
+sqlite3VdbeAddOp2(v, OP_IdxInsert, iTab, r1);
+sqlite3ReleaseTempReg(pParse, r1);
+}
+/*
+** Generate an error message when a SELECT is used within a subexpression
+** (example:  "a IN (SELECT * FROM table)") but it has more than 1 result
+** column.  We do this in a subroutine because the error occurs in multiple
+** places.
+*/
+static int checkForMultiColumnSelectError(
+Parse *pParse,       /* Parse context. */
+SelectDest *pDest,   /* Destination of SELECT results */
+int nExpr            /* Number of result columns returned by SELECT */
+){
+int eDest = pDest->eDest;
+if( nExpr>1 && (eDest==SRT_Mem || eDest==SRT_Set) ){
+sqlite3ErrorMsg(pParse, "only a single result allowed for "
+"a SELECT that is part of an expression");
+return 1;
+}else{
+return 0;
+}
+}
+/*
+** This routine generates the code for the inside of the inner loop
+** of a SELECT.
+**
+** If srcTab and nColumn are both zero, then the pEList expressions
+** are evaluated in order to get the data for this row.  If nColumn>0
+** then data is pulled from srcTab and pEList is used only to get the
+** datatypes for each column.
+*/
+static void selectInnerLoop(
+Parse *pParse,          /* The parser context */
+Select *p,              /* The complete select statement being coded */
+ExprList *pEList,       /* List of values being extracted */
+int srcTab,             /* Pull data from this table */
+int nColumn,            /* Number of columns in the source table */
+ExprList *pOrderBy,     /* If not NULL, sort results using this key */
+int distinct,           /* If >=0, make sure results are distinct */
+SelectDest *pDest,      /* How to dispose of the results */
+int iContinue,          /* Jump here to continue with next row */
+int iBreak              /* Jump here to break out of the inner loop */
+){
+Vdbe *v = pParse->pVdbe;
+int i;
+int hasDistinct;        /* True if the DISTINCT keyword is present */
+int regResult;              /* Start of memory holding result set */
+int eDest = pDest->eDest;   /* How to dispose of results */
+int iParm = pDest->iParm;   /* First argument to disposal method */
+int nResultCol;             /* Number of result columns */
+if( v==0 ) return;
+assert( pEList!=0 );
+hasDistinct = distinct>=0;
+if( pOrderBy==0 && !hasDistinct ){
+codeOffset(v, p, iContinue);
+}
+/* Pull the requested columns.
+*/
+if( nColumn>0 ){
+nResultCol = nColumn;
+}else{
+nResultCol = pEList->nExpr;
+}
+if( pDest->iMem==0 ){
+pDest->iMem = pParse->nMem+1;
+pDest->nMem = nResultCol;
+pParse->nMem += nResultCol;
+}else if( pDest->nMem!=nResultCol ){
+/* This happens when two SELECTs of a compound SELECT have differing
+** numbers of result columns.  The error message will be generated by
+** a higher-level routine. */
+return;
+}
+regResult = pDest->iMem;
+if( nColumn>0 ){
+for(i=0; i<nColumn; i++){
+sqlite3VdbeAddOp3(v, OP_Column, srcTab, i, regResult+i);
+}
+}else if( eDest!=SRT_Exists ){
+/* If the destination is an EXISTS(...) expression, the actual
+** values returned by the SELECT are not required.
+*/
+sqlite3ExprCodeExprList(pParse, pEList, regResult, eDest==SRT_Output);
+}
+nColumn = nResultCol;
+/* If the DISTINCT keyword was present on the SELECT statement
+** and this row has been seen before, then do not make this row
+** part of the result.
+*/
+if( hasDistinct ){
+assert( pEList!=0 );
+assert( pEList->nExpr==nColumn );
+codeDistinct(pParse, distinct, iContinue, nColumn, regResult);
+if( pOrderBy==0 ){
+codeOffset(v, p, iContinue);
+}
+}
+if( checkForMultiColumnSelectError(pParse, pDest, pEList->nExpr) ){
+return;
+}
+switch( eDest ){
+/* In this mode, write each query result to the key of the temporary
+** table iParm.
+*/
+#ifndef SQLITE_OMIT_COMPOUND_SELECT
+case SRT_Union: {
+int r1;
+r1 = sqlite3GetTempReg(pParse);
+sqlite3VdbeAddOp3(v, OP_MakeRecord, regResult, nColumn, r1);
+sqlite3VdbeAddOp2(v, OP_IdxInsert, iParm, r1);
+sqlite3ReleaseTempReg(pParse, r1);
+break;
+}
+/* Construct a record from the query result, but instead of
+** saving that record, use it as a key to delete elements from
+** the temporary table iParm.
+*/
+case SRT_Except: {
+sqlite3VdbeAddOp3(v, OP_IdxDelete, iParm, regResult, nColumn);
+break;
+}
+#endif
+/* Store the result as data using a unique key.
+*/
+case SRT_Table:
+case SRT_EphemTab: {
+int r1 = sqlite3GetTempReg(pParse);
+sqlite3VdbeAddOp3(v, OP_MakeRecord, regResult, nColumn, r1);
+if( pOrderBy ){
+pushOntoSorter(pParse, pOrderBy, p, r1);
+}else{
+int r2 = sqlite3GetTempReg(pParse);
+sqlite3VdbeAddOp2(v, OP_NewRowid, iParm, r2);
+sqlite3VdbeAddOp3(v, OP_Insert, iParm, r1, r2);
+sqlite3VdbeChangeP5(v, OPFLAG_APPEND);
+sqlite3ReleaseTempReg(pParse, r2);
+}
+sqlite3ReleaseTempReg(pParse, r1);
+break;
+}
+#ifndef SQLITE_OMIT_SUBQUERY
+/* If we are creating a set for an "expr IN (SELECT ...)" construct,
+** then there should be a single item on the stack.  Write this
+** item into the set table with bogus data.
+*/
+case SRT_Set: {
+assert( nColumn==1 );
+p->affinity = sqlite3CompareAffinity(pEList->a[0].pExpr, pDest->affinity);
+if( pOrderBy ){
+/* At first glance you would think we could optimize out the
+** ORDER BY in this case since the order of entries in the set
+** does not matter.  But there might be a LIMIT clause, in which
+** case the order does matter */
+pushOntoSorter(pParse, pOrderBy, p, regResult);
+}else{
+int r1 = sqlite3GetTempReg(pParse);
+sqlite3VdbeAddOp4(v, OP_MakeRecord, regResult, 1, r1, &p->affinity, 1);
+sqlite3ExprCacheAffinityChange(pParse, regResult, 1);
+sqlite3VdbeAddOp2(v, OP_IdxInsert, iParm, r1);
+sqlite3ReleaseTempReg(pParse, r1);
+}
+break;
+}
+/* If any row exist in the result set, record that fact and abort.
+*/
+case SRT_Exists: {
+sqlite3VdbeAddOp2(v, OP_Integer, 1, iParm);
+/* The LIMIT clause will terminate the loop for us */
+break;
+}
+/* If this is a scalar select that is part of an expression, then
+** store the results in the appropriate memory cell and break out
+** of the scan loop.
+*/
+case SRT_Mem: {
+assert( nColumn==1 );
+if( pOrderBy ){
+pushOntoSorter(pParse, pOrderBy, p, regResult);
+}else{
+sqlite3ExprCodeMove(pParse, regResult, iParm, 1);
+/* The LIMIT clause will jump out of the loop for us */
+}
+break;
+}
+#endif /* #ifndef SQLITE_OMIT_SUBQUERY */
+/* Send the data to the callback function or to a subroutine.  In the
+** case of a subroutine, the subroutine itself is responsible for
+** popping the data from the stack.
+*/
+case SRT_Coroutine:
+case SRT_Output: {
+if( pOrderBy ){
+int r1 = sqlite3GetTempReg(pParse);
+sqlite3VdbeAddOp3(v, OP_MakeRecord, regResult, nColumn, r1);
+pushOntoSorter(pParse, pOrderBy, p, r1);
+sqlite3ReleaseTempReg(pParse, r1);
+}else if( eDest==SRT_Coroutine ){
+sqlite3VdbeAddOp1(v, OP_Yield, pDest->iParm);
+}else{
+sqlite3VdbeAddOp2(v, OP_ResultRow, regResult, nColumn);
+sqlite3ExprCacheAffinityChange(pParse, regResult, nColumn);
+}
+break;
+}
+#if !defined(SQLITE_OMIT_TRIGGER)
+/* Discard the results.  This is used for SELECT statements inside
+** the body of a TRIGGER.  The purpose of such selects is to call
+** user-defined functions that have side effects.  We do not care
+** about the actual results of the select.
+*/
+default: {
+assert( eDest==SRT_Discard );
+break;
+}
+#endif
+}
+/* Jump to the end of the loop if the LIMIT is reached.
+*/
+if( p->iLimit ){
+assert( pOrderBy==0 );  /* If there is an ORDER BY, the call to
+** pushOntoSorter() would have cleared p->iLimit */
+sqlite3VdbeAddOp2(v, OP_AddImm, p->iLimit, -1);
+sqlite3VdbeAddOp2(v, OP_IfZero, p->iLimit, iBreak);
+}
+}
+/*
+** Given an expression list, generate a KeyInfo structure that records
+** the collating sequence for each expression in that expression list.
+**
+** If the ExprList is an ORDER BY or GROUP BY clause then the resulting
+** KeyInfo structure is appropriate for initializing a virtual index to
+** implement that clause.  If the ExprList is the result set of a SELECT
+** then the KeyInfo structure is appropriate for initializing a virtual
+** index to implement a DISTINCT test.
+**
+** Space to hold the KeyInfo structure is obtain from malloc.  The calling
+** function is responsible for seeing that this structure is eventually
+** freed.  Add the KeyInfo structure to the P4 field of an opcode using
+** P4_KEYINFO_HANDOFF is the usual way of dealing with this.
+*/
+static KeyInfo *keyInfoFromExprList(Parse *pParse, ExprList *pList){
+sqlite3 *db = pParse->db;
+int nExpr;
+KeyInfo *pInfo;
+struct ExprList_item *pItem;
+int i;
+nExpr = pList->nExpr;
+pInfo = sqlite3DbMallocZero(db, sizeof(*pInfo) + nExpr*(sizeof(CollSeq*)+1) );
+if( pInfo ){
+pInfo->aSortOrder = (u8*)&pInfo->aColl[nExpr];
+pInfo->nField = nExpr;
+pInfo->enc = ENC(db);
+for(i=0, pItem=pList->a; i<nExpr; i++, pItem++){
+CollSeq *pColl;
+pColl = sqlite3ExprCollSeq(pParse, pItem->pExpr);
+if( !pColl ){
+pColl = db->pDfltColl;
+}
+pInfo->aColl[i] = pColl;
+pInfo->aSortOrder[i] = pItem->sortOrder;
+}
+}
+return pInfo;
+}
+/*
+** If the inner loop was generated using a non-null pOrderBy argument,
+** then the results were placed in a sorter.  After the loop is terminated
+** we need to run the sorter and output the results.  The following
+** routine generates the code needed to do that.
+*/
+static void generateSortTail(
+Parse *pParse,    /* Parsing context */
+Select *p,        /* The SELECT statement */
+Vdbe *v,          /* Generate code into this VDBE */
+int nColumn,      /* Number of columns of data */
+SelectDest *pDest /* Write the sorted results here */
+){
+int brk = sqlite3VdbeMakeLabel(v);
+int cont = sqlite3VdbeMakeLabel(v);
+int addr;
+int iTab;
+int pseudoTab = 0;
+ExprList *pOrderBy = p->pOrderBy;
+int eDest = pDest->eDest;
+int iParm = pDest->iParm;
+int regRow;
+int regRowid;
+iTab = pOrderBy->iECursor;
+if( eDest==SRT_Output || eDest==SRT_Coroutine ){
+pseudoTab = pParse->nTab++;
+sqlite3VdbeAddOp2(v, OP_SetNumColumns, 0, nColumn);
+sqlite3VdbeAddOp2(v, OP_OpenPseudo, pseudoTab, eDest==SRT_Output);
+}
+addr = 1 + sqlite3VdbeAddOp2(v, OP_Sort, iTab, brk);
+codeOffset(v, p, cont);
+regRow = sqlite3GetTempReg(pParse);
+regRowid = sqlite3GetTempReg(pParse);
+sqlite3VdbeAddOp3(v, OP_Column, iTab, pOrderBy->nExpr + 1, regRow);
+switch( eDest ){
+case SRT_Table:
+case SRT_EphemTab: {
+sqlite3VdbeAddOp2(v, OP_NewRowid, iParm, regRowid);
+sqlite3VdbeAddOp3(v, OP_Insert, iParm, regRow, regRowid);
+sqlite3VdbeChangeP5(v, OPFLAG_APPEND);
+break;
+}
+#ifndef SQLITE_OMIT_SUBQUERY
+case SRT_Set: {
+assert( nColumn==1 );
+sqlite3VdbeAddOp4(v, OP_MakeRecord, regRow, 1, regRowid, &p->affinity, 1);
+sqlite3ExprCacheAffinityChange(pParse, regRow, 1);
+sqlite3VdbeAddOp2(v, OP_IdxInsert, iParm, regRowid);
+break;
+}
+case SRT_Mem: {
+assert( nColumn==1 );
+sqlite3ExprCodeMove(pParse, regRow, iParm, 1);
+/* The LIMIT clause will terminate the loop for us */
+break;
+}
+#endif
+case SRT_Output:
+case SRT_Coroutine: {
+int i;
+sqlite3VdbeAddOp2(v, OP_Integer, 1, regRowid);
+sqlite3VdbeAddOp3(v, OP_Insert, pseudoTab, regRow, regRowid);
+for(i=0; i<nColumn; i++){
+assert( regRow!=pDest->iMem+i );
+sqlite3VdbeAddOp3(v, OP_Column, pseudoTab, i, pDest->iMem+i);
+}
+if( eDest==SRT_Output ){
+sqlite3VdbeAddOp2(v, OP_ResultRow, pDest->iMem, nColumn);
+sqlite3ExprCacheAffinityChange(pParse, pDest->iMem, nColumn);
+}else{
+sqlite3VdbeAddOp1(v, OP_Yield, pDest->iParm);
+}
+break;
+}
+default: {
+/* Do nothing */
+break;
+}
+}
+sqlite3ReleaseTempReg(pParse, regRow);
+sqlite3ReleaseTempReg(pParse, regRowid);
+/* LIMIT has been implemented by the pushOntoSorter() routine.
+*/
+assert( p->iLimit==0 );
+/* The bottom of the loop
+*/
+sqlite3VdbeResolveLabel(v, cont);
+sqlite3VdbeAddOp2(v, OP_Next, iTab, addr);
+sqlite3VdbeResolveLabel(v, brk);
+if( eDest==SRT_Output || eDest==SRT_Coroutine ){
+sqlite3VdbeAddOp2(v, OP_Close, pseudoTab, 0);
+}
+}
+/*
+** Return a pointer to a string containing the 'declaration type' of the
+** expression pExpr. The string may be treated as static by the caller.
+**
+** The declaration type is the exact datatype definition extracted from the
+** original CREATE TABLE statement if the expression is a column. The
+** declaration type for a ROWID field is INTEGER. Exactly when an expression
+** is considered a column can be complex in the presence of subqueries. The
+** result-set expression in all of the following SELECT statements is
+** considered a column by this function.
+**
+**   SELECT col FROM tbl;
+**   SELECT (SELECT col FROM tbl;
+**   SELECT (SELECT col FROM tbl);
+**   SELECT abc FROM (SELECT col AS abc FROM tbl);
+**
+** The declaration type for any expression other than a column is NULL.
+*/
+static const char *columnType(
+NameContext *pNC,
+Expr *pExpr,
+const char **pzOriginDb,
+const char **pzOriginTab,
+const char **pzOriginCol
+){
+char const *zType = 0;
+char const *zOriginDb = 0;
+char const *zOriginTab = 0;
+char const *zOriginCol = 0;
+int j;
+if( pExpr==0 || pNC->pSrcList==0 ) return 0;
+switch( pExpr->op ){
+case TK_AGG_COLUMN:
+case TK_COLUMN: {
+/* The expression is a column. Locate the table the column is being
+** extracted from in NameContext.pSrcList. This table may be real
+** database table or a subquery.
+*/
+Table *pTab = 0;            /* Table structure column is extracted from */
+Select *pS = 0;             /* Select the column is extracted from */
+int iCol = pExpr->iColumn;  /* Index of column in pTab */
+while( pNC && !pTab ){
+SrcList *pTabList = pNC->pSrcList;
+for(j=0;j<pTabList->nSrc && pTabList->a[j].iCursor!=pExpr->iTable;j++);
+if( j<pTabList->nSrc ){
+pTab = pTabList->a[j].pTab;
+pS = pTabList->a[j].pSelect;
+}else{
+pNC = pNC->pNext;
+}
+}
+if( pTab==0 ){
+/* FIX ME:
+** This can occurs if you have something like "SELECT new.x;" inside
+** a trigger.  In other words, if you reference the special "new"
+** table in the result set of a select.  We do not have a good way
+** to find the actual table type, so call it "TEXT".  This is really
+** something of a bug, but I do not know how to fix it.
+**
+** This code does not produce the correct answer - it just prevents
+** a segfault.  See ticket #1229.
+*/
+zType = "TEXT";
+break;
+}
+assert( pTab );
+if( pS ){
+/* The "table" is actually a sub-select or a view in the FROM clause
+** of the SELECT statement. Return the declaration type and origin
+** data for the result-set column of the sub-select.
+*/
+if( iCol>=0 && iCol<pS->pEList->nExpr ){
+/* If iCol is less than zero, then the expression requests the
+** rowid of the sub-select or view. This expression is legal (see
+** test case misc2.2.2) - it always evaluates to NULL.
+*/
+NameContext sNC;
+Expr *p = pS->pEList->a[iCol].pExpr;
+sNC.pSrcList = pS->pSrc;
+sNC.pNext = 0;
+sNC.pParse = pNC->pParse;
+zType = columnType(&sNC, p, &zOriginDb, &zOriginTab, &zOriginCol);
+}
+}else if( pTab->pSchema ){
+/* A real table */
+assert( !pS );
+if( iCol<0 ) iCol = pTab->iPKey;
+assert( iCol==-1 || (iCol>=0 && iCol<pTab->nCol) );
+if( iCol<0 ){
+zType = "INTEGER";
+zOriginCol = "rowid";
+}else{
+zType = pTab->aCol[iCol].zType;
+zOriginCol = pTab->aCol[iCol].zName;
+}
+zOriginTab = pTab->zName;
+if( pNC->pParse ){
+int iDb = sqlite3SchemaToIndex(pNC->pParse->db, pTab->pSchema);
+zOriginDb = pNC->pParse->db->aDb[iDb].zName;
+}
+}
+break;
+}
+#ifndef SQLITE_OMIT_SUBQUERY
+case TK_SELECT: {
+/* The expression is a sub-select. Return the declaration type and
+** origin info for the single column in the result set of the SELECT
+** statement.
+*/
+NameContext sNC;
+Select *pS = pExpr->pSelect;
+Expr *p = pS->pEList->a[0].pExpr;
+sNC.pSrcList = pS->pSrc;
+sNC.pNext = pNC;
+sNC.pParse = pNC->pParse;
+zType = columnType(&sNC, p, &zOriginDb, &zOriginTab, &zOriginCol);
+break;
+}
+#endif
+}
+if( pzOriginDb ){
+assert( pzOriginTab && pzOriginCol );
+*pzOriginDb = zOriginDb;
+*pzOriginTab = zOriginTab;
+*pzOriginCol = zOriginCol;
+}
+return zType;
+}
+/*
+** Generate code that will tell the VDBE the declaration types of columns
+** in the result set.
+*/
+static void generateColumnTypes(
+Parse *pParse,      /* Parser context */
+SrcList *pTabList,  /* List of tables */
+ExprList *pEList    /* Expressions defining the result set */
+){
+#ifndef SQLITE_OMIT_DECLTYPE
+Vdbe *v = pParse->pVdbe;
+int i;
+NameContext sNC;
+sNC.pSrcList = pTabList;
+sNC.pParse = pParse;
+for(i=0; i<pEList->nExpr; i++){
+Expr *p = pEList->a[i].pExpr;
+const char *zType;
+#ifdef SQLITE_ENABLE_COLUMN_METADATA
+const char *zOrigDb = 0;
+const char *zOrigTab = 0;
+const char *zOrigCol = 0;
+zType = columnType(&sNC, p, &zOrigDb, &zOrigTab, &zOrigCol);
+/* The vdbe must make its own copy of the column-type and other
+** column specific strings, in case the schema is reset before this
+** virtual machine is deleted.
+*/
+sqlite3VdbeSetColName(v, i, COLNAME_DATABASE, zOrigDb, P4_TRANSIENT);
+sqlite3VdbeSetColName(v, i, COLNAME_TABLE, zOrigTab, P4_TRANSIENT);
+sqlite3VdbeSetColName(v, i, COLNAME_COLUMN, zOrigCol, P4_TRANSIENT);
+#else
+zType = columnType(&sNC, p, 0, 0, 0);
+#endif
+sqlite3VdbeSetColName(v, i, COLNAME_DECLTYPE, zType, P4_TRANSIENT);
+}
+#endif /* SQLITE_OMIT_DECLTYPE */
+}
+/*
+** Generate code that will tell the VDBE the names of columns
+** in the result set.  This information is used to provide the
+** azCol[] values in the callback.
+*/
+static void generateColumnNames(
+Parse *pParse,      /* Parser context */
+SrcList *pTabList,  /* List of tables */
+ExprList *pEList    /* Expressions defining the result set */
+){
+Vdbe *v = pParse->pVdbe;
+int i, j;
+sqlite3 *db = pParse->db;
+int fullNames, shortNames;
+#ifndef SQLITE_OMIT_EXPLAIN
+/* If this is an EXPLAIN, skip this step */
+if( pParse->explain ){
+return;
+}
+#endif
+assert( v!=0 );
+if( pParse->colNamesSet || v==0 || db->mallocFailed ) return;
+pParse->colNamesSet = 1;
+fullNames = (db->flags & SQLITE_FullColNames)!=0;
+shortNames = (db->flags & SQLITE_ShortColNames)!=0;
+sqlite3VdbeSetNumCols(v, pEList->nExpr);
+for(i=0; i<pEList->nExpr; i++){
+Expr *p;
+p = pEList->a[i].pExpr;
+if( p==0 ) continue;
+if( pEList->a[i].zName ){
+char *zName = pEList->a[i].zName;
+sqlite3VdbeSetColName(v, i, COLNAME_NAME, zName, strlen(zName));
+}else if( (p->op==TK_COLUMN || p->op==TK_AGG_COLUMN) && pTabList ){
+Table *pTab;
+char *zCol;
+int iCol = p->iColumn;
+for(j=0; j<pTabList->nSrc && pTabList->a[j].iCursor!=p->iTable; j++){}
+assert( j<pTabList->nSrc );
+pTab = pTabList->a[j].pTab;
+if( iCol<0 ) iCol = pTab->iPKey;
+assert( iCol==-1 || (iCol>=0 && iCol<pTab->nCol) );
+if( iCol<0 ){
+zCol = "rowid";
+}else{
+zCol = pTab->aCol[iCol].zName;
+}
+if( !shortNames && !fullNames ){
+sqlite3VdbeSetColName(v, i, COLNAME_NAME, (char*)p->span.z, p->span.n);
+}else if( fullNames || (!shortNames && pTabList->nSrc>1) ){
+char *zName = 0;
+char *zTab;
+zTab = pTabList->a[j].zAlias;
+if( fullNames || zTab==0 ) zTab = pTab->zName;
+zName = sqlite3MPrintf(db, "%s.%s", zTab, zCol);
+sqlite3VdbeSetColName(v, i, COLNAME_NAME, zName, P4_DYNAMIC);
+}else{
+sqlite3VdbeSetColName(v, i, COLNAME_NAME, zCol, strlen(zCol));
+}
+}else{
+sqlite3VdbeSetColName(v, i, COLNAME_NAME, (char*)p->span.z, p->span.n);
+}
+}
+generateColumnTypes(pParse, pTabList, pEList);
+}
+#ifndef SQLITE_OMIT_COMPOUND_SELECT
+/*
+** Name of the connection operator, used for error messages.
+*/
+static const char *selectOpName(int id){
+char *z;
+switch( id ){
+case TK_ALL:       z = "UNION ALL";   break;
+case TK_INTERSECT: z = "INTERSECT";   break;
+case TK_EXCEPT:    z = "EXCEPT";      break;
+default:           z = "UNION";       break;
+}
+return z;
+}
+#endif /* SQLITE_OMIT_COMPOUND_SELECT */
+/*
+** Given a an expression list (which is really the list of expressions
+** that form the result set of a SELECT statement) compute appropriate
+** column names for a table that would hold the expression list.
+**
+** All column names will be unique.
+**
+** Only the column names are computed.  Column.zType, Column.zColl,
+** and other fields of Column are zeroed.
+**
+** Return SQLITE_OK on success.  If a memory allocation error occurs,
+** store NULL in *paCol and 0 in *pnCol and return SQLITE_NOMEM.
+*/
+static int selectColumnsFromExprList(
+Parse *pParse,          /* Parsing context */
+ExprList *pEList,       /* Expr list from which to derive column names */
+int *pnCol,             /* Write the number of columns here */
+Column **paCol          /* Write the new column list here */
+){
+sqlite3 *db = pParse->db;
+int i, j, cnt;
+Column *aCol, *pCol;
+int nCol;
+Expr *p;
+char *zName;
+int nName;
+*pnCol = nCol = pEList->nExpr;
+aCol = *paCol = sqlite3DbMallocZero(db, sizeof(aCol[0])*nCol);
+if( aCol==0 ) return SQLITE_NOMEM;
+for(i=0, pCol=aCol; i<nCol; i++, pCol++){
+/* Get an appropriate name for the column
+*/
+p = pEList->a[i].pExpr;
+assert( p->pRight==0 || p->pRight->token.z==0 || p->pRight->token.z[0]!=0 );
+if( (zName = pEList->a[i].zName)!=0 ){
+/* If the column contains an "AS <name>" phrase, use <name> as the name */
+zName = sqlite3DbStrDup(db, zName);
+}else{
+Expr *pCol = p;
+Table *pTab;
+while( pCol->op==TK_DOT ) pCol = pCol->pRight;
+if( pCol->op==TK_COLUMN && (pTab = pCol->pTab)!=0 ){
+/* For columns use the column name name */
+int iCol = pCol->iColumn;
+if( iCol<0 ) iCol = pTab->iPKey;
+zName = sqlite3MPrintf(db, "%s",
+iCol>=0 ? pTab->aCol[iCol].zName : "rowid");
+}else{
+/* Use the original text of the column expression as its name */
+zName = sqlite3MPrintf(db, "%T", &pCol->span);
+}
+}
+if( db->mallocFailed ){
+sqlite3DbFree(db, zName);
+break;
+}
+sqlite3Dequote(zName);
+/* Make sure the column name is unique.  If the name is not unique,
+** append a integer to the name so that it becomes unique.
+*/
+nName = strlen(zName);
+for(j=cnt=0; j<i; j++){
+if( sqlite3StrICmp(aCol[j].zName, zName)==0 ){
+char *zNewName;
+zName[nName] = 0;
+zNewName = sqlite3MPrintf(db, "%s:%d", zName, ++cnt);
+sqlite3DbFree(db, zName);
+zName = zNewName;
+j = -1;
+if( zName==0 ) break;
+}
+}
+pCol->zName = zName;
+}
+if( db->mallocFailed ){
+int j;
+for(j=0; j<i; j++){
+sqlite3DbFree(db, aCol[j].zName);
+}
+sqlite3DbFree(db, aCol);
+*paCol = 0;
+*pnCol = 0;
+return SQLITE_NOMEM;
+}
+return SQLITE_OK;
+}
+/*
+** Add type and collation information to a column list based on
+** a SELECT statement.
+**
+** The column list presumably came from selectColumnNamesFromExprList().
+** The column list has only names, not types or collations.  This
+** routine goes through and adds the types and collations.
+**
+** This routine requires that all indentifiers in the SELECT
+** statement be resolved.
+*/
+static void selectAddColumnTypeAndCollation(
+Parse *pParse,        /* Parsing contexts */
+int nCol,             /* Number of columns */
+Column *aCol,         /* List of columns */
+Select *pSelect       /* SELECT used to determine types and collations */
+){
+sqlite3 *db = pParse->db;
+NameContext sNC;
+Column *pCol;
+CollSeq *pColl;
+int i;
+Expr *p;
+struct ExprList_item *a;
+assert( pSelect!=0 );
+assert( (pSelect->selFlags & SF_Resolved)!=0 );
+assert( nCol==pSelect->pEList->nExpr || db->mallocFailed );
+if( db->mallocFailed ) return;
+memset(&sNC, 0, sizeof(sNC));
+sNC.pSrcList = pSelect->pSrc;
+a = pSelect->pEList->a;
+for(i=0, pCol=aCol; i<nCol; i++, pCol++){
+p = a[i].pExpr;
+pCol->zType = sqlite3DbStrDup(db, columnType(&sNC, p, 0, 0, 0));
+pCol->affinity = sqlite3ExprAffinity(p);
+pColl = sqlite3ExprCollSeq(pParse, p);
+if( pColl ){
+pCol->zColl = sqlite3DbStrDup(db, pColl->zName);
+}
+}
+}
+/*
+** Given a SELECT statement, generate a Table structure that describes
+** the result set of that SELECT.
+*/
+Table *sqlite3ResultSetOfSelect(Parse *pParse, Select *pSelect){
+Table *pTab;
+sqlite3 *db = pParse->db;
+int savedFlags;
+savedFlags = db->flags;
+db->flags &= ~SQLITE_FullColNames;
+db->flags |= SQLITE_ShortColNames;
+sqlite3SelectPrep(pParse, pSelect, 0);
+if( pParse->nErr ) return 0;
+while( pSelect->pPrior ) pSelect = pSelect->pPrior;
+db->flags = savedFlags;
+pTab = sqlite3DbMallocZero(db, sizeof(Table) );
+if( pTab==0 ){
+return 0;
+}
+pTab->db = db;
+pTab->nRef = 1;
+pTab->zName = 0;
+selectColumnsFromExprList(pParse, pSelect->pEList, &pTab->nCol, &pTab->aCol);
+selectAddColumnTypeAndCollation(pParse, pTab->nCol, pTab->aCol, pSelect);
+pTab->iPKey = -1;
+if( db->mallocFailed ){
+sqlite3DeleteTable(pTab);
+return 0;
+}
+return pTab;
+}
+/*
+** Get a VDBE for the given parser context.  Create a new one if necessary.
+** If an error occurs, return NULL and leave a message in pParse.
+*/
+Vdbe *sqlite3GetVdbe(Parse *pParse){
+Vdbe *v = pParse->pVdbe;
+if( v==0 ){
+v = pParse->pVdbe = sqlite3VdbeCreate(pParse->db);
+#ifndef SQLITE_OMIT_TRACE
+if( v ){
+sqlite3VdbeAddOp0(v, OP_Trace);
+}
+#endif
+}
+return v;
+}
+/*
+** Compute the iLimit and iOffset fields of the SELECT based on the
+** pLimit and pOffset expressions.  pLimit and pOffset hold the expressions
+** that appear in the original SQL statement after the LIMIT and OFFSET
+** keywords.  Or NULL if those keywords are omitted. iLimit and iOffset
+** are the integer memory register numbers for counters used to compute
+** the limit and offset.  If there is no limit and/or offset, then
+** iLimit and iOffset are negative.
+**
+** This routine changes the values of iLimit and iOffset only if
+** a limit or offset is defined by pLimit and pOffset.  iLimit and
+** iOffset should have been preset to appropriate default values
+** (usually but not always -1) prior to calling this routine.
+** Only if pLimit!=0 or pOffset!=0 do the limit registers get
+** redefined.  The UNION ALL operator uses this property to force
+** the reuse of the same limit and offset registers across multiple
+** SELECT statements.
+*/
+static void computeLimitRegisters(Parse *pParse, Select *p, int iBreak){
+Vdbe *v = 0;
+int iLimit = 0;
+int iOffset;
+int addr1;
+if( p->iLimit ) return;
+/*
+** "LIMIT -1" always shows all rows.  There is some
+** contraversy about what the correct behavior should be.
+** The current implementation interprets "LIMIT 0" to mean
+** no rows.
+*/
+if( p->pLimit ){
+p->iLimit = iLimit = ++pParse->nMem;
+v = sqlite3GetVdbe(pParse);
+if( v==0 ) return;
+sqlite3ExprCode(pParse, p->pLimit, iLimit);
+sqlite3VdbeAddOp1(v, OP_MustBeInt, iLimit);
+VdbeComment((v, "LIMIT counter"));
+sqlite3VdbeAddOp2(v, OP_IfZero, iLimit, iBreak);
+}
+if( p->pOffset ){
+p->iOffset = iOffset = ++pParse->nMem;
+if( p->pLimit ){
+pParse->nMem++;   /* Allocate an extra register for limit+offset */
+}
+v = sqlite3GetVdbe(pParse);
+if( v==0 ) return;
+sqlite3ExprCode(pParse, p->pOffset, iOffset);
+sqlite3VdbeAddOp1(v, OP_MustBeInt, iOffset);
+VdbeComment((v, "OFFSET counter"));
+addr1 = sqlite3VdbeAddOp1(v, OP_IfPos, iOffset);
+sqlite3VdbeAddOp2(v, OP_Integer, 0, iOffset);
+sqlite3VdbeJumpHere(v, addr1);
+if( p->pLimit ){
+sqlite3VdbeAddOp3(v, OP_Add, iLimit, iOffset, iOffset+1);
+VdbeComment((v, "LIMIT+OFFSET"));
+addr1 = sqlite3VdbeAddOp1(v, OP_IfPos, iLimit);
+sqlite3VdbeAddOp2(v, OP_Integer, -1, iOffset+1);
+sqlite3VdbeJumpHere(v, addr1);
+}
+}
+}
+#ifndef SQLITE_OMIT_COMPOUND_SELECT
+/*
+** Return the appropriate collating sequence for the iCol-th column of
+** the result set for the compound-select statement "p".  Return NULL if
+** the column has no default collating sequence.
+**
+** The collating sequence for the compound select is taken from the
+** left-most term of the select that has a collating sequence.
+*/
+static CollSeq *multiSelectCollSeq(Parse *pParse, Select *p, int iCol){
+CollSeq *pRet;
+if( p->pPrior ){
+pRet = multiSelectCollSeq(pParse, p->pPrior, iCol);
+}else{
+pRet = 0;
+}
+if( pRet==0 ){
+pRet = sqlite3ExprCollSeq(pParse, p->pEList->a[iCol].pExpr);
+}
+return pRet;
+}
+#endif /* SQLITE_OMIT_COMPOUND_SELECT */
+/* Forward reference */
+static int multiSelectOrderBy(
+Parse *pParse,        /* Parsing context */
+Select *p,            /* The right-most of SELECTs to be coded */
+SelectDest *pDest     /* What to do with query results */
+);
+#ifndef SQLITE_OMIT_COMPOUND_SELECT
+/*
+** This routine is called to process a compound query form from
+** two or more separate queries using UNION, UNION ALL, EXCEPT, or
+** INTERSECT
+**
+** "p" points to the right-most of the two queries.  the query on the
+** left is p->pPrior.  The left query could also be a compound query
+** in which case this routine will be called recursively.
+**
+** The results of the total query are to be written into a destination
+** of type eDest with parameter iParm.
+**
+** Example 1:  Consider a three-way compound SQL statement.
+**
+**     SELECT a FROM t1 UNION SELECT b FROM t2 UNION SELECT c FROM t3
+**
+** This statement is parsed up as follows:
+**
+**     SELECT c FROM t3
+**      |
+**      `----->  SELECT b FROM t2
+**                |
+**                `------>  SELECT a FROM t1
+**
+** The arrows in the diagram above represent the Select.pPrior pointer.
+** So if this routine is called with p equal to the t3 query, then
+** pPrior will be the t2 query.  p->op will be TK_UNION in this case.
+**
+** Notice that because of the way SQLite parses compound SELECTs, the
+** individual selects always group from left to right.
+*/
+static int multiSelect(
+Parse *pParse,        /* Parsing context */
+Select *p,            /* The right-most of SELECTs to be coded */
+SelectDest *pDest     /* What to do with query results */
+){
+int rc = SQLITE_OK;   /* Success code from a subroutine */
+Select *pPrior;       /* Another SELECT immediately to our left */
+Vdbe *v;              /* Generate code to this VDBE */
+SelectDest dest;      /* Alternative data destination */
+Select *pDelete = 0;  /* Chain of simple selects to delete */
+sqlite3 *db;          /* Database connection */
+/* Make sure there is no ORDER BY or LIMIT clause on prior SELECTs.  Only
+** the last (right-most) SELECT in the series may have an ORDER BY or LIMIT.
+*/
+assert( p && p->pPrior );  /* Calling function guarantees this much */
+db = pParse->db;
+pPrior = p->pPrior;
+assert( pPrior->pRightmost!=pPrior );
+assert( pPrior->pRightmost==p->pRightmost );
+dest = *pDest;
+if( pPrior->pOrderBy ){
+sqlite3ErrorMsg(pParse,"ORDER BY clause should come after %s not before",
+selectOpName(p->op));
+rc = 1;
+goto multi_select_end;
+}
+if( pPrior->pLimit ){
+sqlite3ErrorMsg(pParse,"LIMIT clause should come after %s not before",
+selectOpName(p->op));
+rc = 1;
+goto multi_select_end;
+}
+v = sqlite3GetVdbe(pParse);
+assert( v!=0 );  /* The VDBE already created by calling function */
+/* Create the destination temporary table if necessary
+*/
+if( dest.eDest==SRT_EphemTab ){
+assert( p->pEList );
+sqlite3VdbeAddOp2(v, OP_OpenEphemeral, dest.iParm, p->pEList->nExpr);
+dest.eDest = SRT_Table;
+}
+/* Make sure all SELECTs in the statement have the same number of elements
+** in their result sets.
+*/
+assert( p->pEList && pPrior->pEList );
+if( p->pEList->nExpr!=pPrior->pEList->nExpr ){
+sqlite3ErrorMsg(pParse, "SELECTs to the left and right of %s"
+" do not have the same number of result columns", selectOpName(p->op));
+rc = 1;
+goto multi_select_end;
+}
+/* Compound SELECTs that have an ORDER BY clause are handled separately.
+*/
+if( p->pOrderBy ){
+return multiSelectOrderBy(pParse, p, pDest);
+}
+/* Generate code for the left and right SELECT statements.
+*/
+switch( p->op ){
+case TK_ALL: {
+int addr = 0;
+assert( !pPrior->pLimit );
+pPrior->pLimit = p->pLimit;
+pPrior->pOffset = p->pOffset;
+rc = sqlite3Select(pParse, pPrior, &dest);
+p->pLimit = 0;
+p->pOffset = 0;
+if( rc ){
+goto multi_select_end;
+}
+p->pPrior = 0;
+p->iLimit = pPrior->iLimit;
+p->iOffset = pPrior->iOffset;
+if( p->iLimit ){
+addr = sqlite3VdbeAddOp1(v, OP_IfZero, p->iLimit);
+VdbeComment((v, "Jump ahead if LIMIT reached"));
+}
+rc = sqlite3Select(pParse, p, &dest);
+pDelete = p->pPrior;
+p->pPrior = pPrior;
+if( rc ){
+goto multi_select_end;
+}
+if( addr ){
+sqlite3VdbeJumpHere(v, addr);
+}
+break;
+}
+case TK_EXCEPT:
+case TK_UNION: {
+int unionTab;    /* Cursor number of the temporary table holding result */
+int op = 0;      /* One of the SRT_ operations to apply to self */
+int priorOp;     /* The SRT_ operation to apply to prior selects */
+Expr *pLimit, *pOffset; /* Saved values of p->nLimit and p->nOffset */
+int addr;
+SelectDest uniondest;
+priorOp = SRT_Union;
+if( dest.eDest==priorOp && !p->pLimit && !p->pOffset ){
+/* We can reuse a temporary table generated by a SELECT to our
+** right.
+*/
+unionTab = dest.iParm;
+}else{
+/* We will need to create our own temporary table to hold the
+** intermediate results.
+*/
+unionTab = pParse->nTab++;
+assert( p->pOrderBy==0 );
+addr = sqlite3VdbeAddOp2(v, OP_OpenEphemeral, unionTab, 0);
+assert( p->addrOpenEphm[0] == -1 );
+p->addrOpenEphm[0] = addr;
+p->pRightmost->selFlags |= SF_UsesEphemeral;
+assert( p->pEList );
+}
+/* Code the SELECT statements to our left
+*/
+assert( !pPrior->pOrderBy );
+sqlite3SelectDestInit(&uniondest, priorOp, unionTab);
+rc = sqlite3Select(pParse, pPrior, &uniondest);
+if( rc ){
+goto multi_select_end;
+}
+/* Code the current SELECT statement
+*/
+if( p->op==TK_EXCEPT ){
+op = SRT_Except;
+}else{
+assert( p->op==TK_UNION );
+op = SRT_Union;
+}
+p->pPrior = 0;
+pLimit = p->pLimit;
+p->pLimit = 0;
+pOffset = p->pOffset;
+p->pOffset = 0;
+uniondest.eDest = op;
+rc = sqlite3Select(pParse, p, &uniondest);
+/* Query flattening in sqlite3Select() might refill p->pOrderBy.
+** Be sure to delete p->pOrderBy, therefore, to avoid a memory leak. */
+sqlite3ExprListDelete(db, p->pOrderBy);
+pDelete = p->pPrior;
+p->pPrior = pPrior;
+p->pOrderBy = 0;
+sqlite3ExprDelete(db, p->pLimit);
+p->pLimit = pLimit;
+p->pOffset = pOffset;
+p->iLimit = 0;
+p->iOffset = 0;
+if( rc ){
+goto multi_select_end;
+}
+/* Convert the data in the temporary table into whatever form
+** it is that we currently need.
+*/
+if( dest.eDest!=priorOp || unionTab!=dest.iParm ){
+int iCont, iBreak, iStart;
+assert( p->pEList );
+if( dest.eDest==SRT_Output ){
+Select *pFirst = p;
+while( pFirst->pPrior ) pFirst = pFirst->pPrior;
+generateColumnNames(pParse, 0, pFirst->pEList);
+}
+iBreak = sqlite3VdbeMakeLabel(v);
+iCont = sqlite3VdbeMakeLabel(v);
+computeLimitRegisters(pParse, p, iBreak);
+sqlite3VdbeAddOp2(v, OP_Rewind, unionTab, iBreak);
+iStart = sqlite3VdbeCurrentAddr(v);
+selectInnerLoop(pParse, p, p->pEList, unionTab, p->pEList->nExpr,
+0, -1, &dest, iCont, iBreak);
+sqlite3VdbeResolveLabel(v, iCont);
+sqlite3VdbeAddOp2(v, OP_Next, unionTab, iStart);
+sqlite3VdbeResolveLabel(v, iBreak);
+sqlite3VdbeAddOp2(v, OP_Close, unionTab, 0);
+}
+break;
+}
+case TK_INTERSECT: {
+int tab1, tab2;
+int iCont, iBreak, iStart;
+Expr *pLimit, *pOffset;
+int addr;
+SelectDest intersectdest;
+int r1;
+/* INTERSECT is different from the others since it requires
+** two temporary tables.  Hence it has its own case.  Begin
+** by allocating the tables we will need.
+*/
+tab1 = pParse->nTab++;
+tab2 = pParse->nTab++;
+assert( p->pOrderBy==0 );
+addr = sqlite3VdbeAddOp2(v, OP_OpenEphemeral, tab1, 0);
+assert( p->addrOpenEphm[0] == -1 );
+p->addrOpenEphm[0] = addr;
+p->pRightmost->selFlags |= SF_UsesEphemeral;
+assert( p->pEList );
+/* Code the SELECTs to our left into temporary table "tab1".
+*/
+sqlite3SelectDestInit(&intersectdest, SRT_Union, tab1);
+rc = sqlite3Select(pParse, pPrior, &intersectdest);
+if( rc ){
+goto multi_select_end;
+}
+/* Code the current SELECT into temporary table "tab2"
+*/
+addr = sqlite3VdbeAddOp2(v, OP_OpenEphemeral, tab2, 0);
+assert( p->addrOpenEphm[1] == -1 );
+p->addrOpenEphm[1] = addr;
+p->pPrior = 0;
+pLimit = p->pLimit;
+p->pLimit = 0;
+pOffset = p->pOffset;
+p->pOffset = 0;
+intersectdest.iParm = tab2;
+rc = sqlite3Select(pParse, p, &intersectdest);
+pDelete = p->pPrior;
+p->pPrior = pPrior;
+sqlite3ExprDelete(db, p->pLimit);
+p->pLimit = pLimit;
+p->pOffset = pOffset;
+if( rc ){
+goto multi_select_end;
+}
+/* Generate code to take the intersection of the two temporary
+** tables.
+*/
+assert( p->pEList );
+if( dest.eDest==SRT_Output ){
+Select *pFirst = p;
+while( pFirst->pPrior ) pFirst = pFirst->pPrior;
+generateColumnNames(pParse, 0, pFirst->pEList);
+}
+iBreak = sqlite3VdbeMakeLabel(v);
+iCont = sqlite3VdbeMakeLabel(v);
+computeLimitRegisters(pParse, p, iBreak);
+sqlite3VdbeAddOp2(v, OP_Rewind, tab1, iBreak);
+r1 = sqlite3GetTempReg(pParse);
+iStart = sqlite3VdbeAddOp2(v, OP_RowKey, tab1, r1);
+sqlite3VdbeAddOp3(v, OP_NotFound, tab2, iCont, r1);
+sqlite3ReleaseTempReg(pParse, r1);
+selectInnerLoop(pParse, p, p->pEList, tab1, p->pEList->nExpr,
+0, -1, &dest, iCont, iBreak);
+sqlite3VdbeResolveLabel(v, iCont);
+sqlite3VdbeAddOp2(v, OP_Next, tab1, iStart);
+sqlite3VdbeResolveLabel(v, iBreak);
+sqlite3VdbeAddOp2(v, OP_Close, tab2, 0);
+sqlite3VdbeAddOp2(v, OP_Close, tab1, 0);
+break;
+}
+}
+/* Compute collating sequences used by
+** temporary tables needed to implement the compound select.
+** Attach the KeyInfo structure to all temporary tables.
+**
+** This section is run by the right-most SELECT statement only.
+** SELECT statements to the left always skip this part.  The right-most
+** SELECT might also skip this part if it has no ORDER BY clause and
+** no temp tables are required.
+*/
+if( p->selFlags & SF_UsesEphemeral ){
+int i;                        /* Loop counter */
+KeyInfo *pKeyInfo;            /* Collating sequence for the result set */
+Select *pLoop;                /* For looping through SELECT statements */
+CollSeq **apColl;             /* For looping through pKeyInfo->aColl[] */
+int nCol;                     /* Number of columns in result set */
+assert( p->pRightmost==p );
+nCol = p->pEList->nExpr;
+pKeyInfo = sqlite3DbMallocZero(db,
+sizeof(*pKeyInfo)+nCol*(sizeof(CollSeq*) + 1));
+if( !pKeyInfo ){
+rc = SQLITE_NOMEM;
+goto multi_select_end;
+}
+pKeyInfo->enc = ENC(db);
+pKeyInfo->nField = nCol;
+for(i=0, apColl=pKeyInfo->aColl; i<nCol; i++, apColl++){
+*apColl = multiSelectCollSeq(pParse, p, i);
+if( 0==*apColl ){
+*apColl = db->pDfltColl;
+}
+}
+for(pLoop=p; pLoop; pLoop=pLoop->pPrior){
+for(i=0; i<2; i++){
+int addr = pLoop->addrOpenEphm[i];
+if( addr<0 ){
+/* If [0] is unused then [1] is also unused.  So we can
+** always safely abort as soon as the first unused slot is found */
+assert( pLoop->addrOpenEphm[1]<0 );
+break;
+}
+sqlite3VdbeChangeP2(v, addr, nCol);
+sqlite3VdbeChangeP4(v, addr, (char*)pKeyInfo, P4_KEYINFO);
+pLoop->addrOpenEphm[i] = -1;
+}
+}
+sqlite3DbFree(db, pKeyInfo);
+}
+multi_select_end:
+pDest->iMem = dest.iMem;
+pDest->nMem = dest.nMem;
+sqlite3SelectDelete(db, pDelete);
+return rc;
+}
+#endif /* SQLITE_OMIT_COMPOUND_SELECT */
+/*
+** Code an output subroutine for a coroutine implementation of a
+** SELECT statment.
+**
+** The data to be output is contained in pIn->iMem.  There are
+** pIn->nMem columns to be output.  pDest is where the output should
+** be sent.
+**
+** regReturn is the number of the register holding the subroutine
+** return address.
+**
+** If regPrev>0 then it is a the first register in a vector that
+** records the previous output.  mem[regPrev] is a flag that is false
+** if there has been no previous output.  If regPrev>0 then code is
+** generated to suppress duplicates.  pKeyInfo is used for comparing
+** keys.
+**
+** If the LIMIT found in p->iLimit is reached, jump immediately to
+** iBreak.
+*/
+static int generateOutputSubroutine(
+Parse *pParse,          /* Parsing context */
+Select *p,              /* The SELECT statement */
+SelectDest *pIn,        /* Coroutine supplying data */
+SelectDest *pDest,      /* Where to send the data */
+int regReturn,          /* The return address register */
+int regPrev,            /* Previous result register.  No uniqueness if 0 */
+KeyInfo *pKeyInfo,      /* For comparing with previous entry */
+int p4type,             /* The p4 type for pKeyInfo */
+int iBreak              /* Jump here if we hit the LIMIT */
+){
+Vdbe *v = pParse->pVdbe;
+int iContinue;
+int addr;
+addr = sqlite3VdbeCurrentAddr(v);
+iContinue = sqlite3VdbeMakeLabel(v);
+/* Suppress duplicates for UNION, EXCEPT, and INTERSECT
+*/
+if( regPrev ){
+int j1, j2;
+j1 = sqlite3VdbeAddOp1(v, OP_IfNot, regPrev);
+j2 = sqlite3VdbeAddOp4(v, OP_Compare, pIn->iMem, regPrev+1, pIn->nMem,
+(char*)pKeyInfo, p4type);
+sqlite3VdbeAddOp3(v, OP_Jump, j2+2, iContinue, j2+2);
+sqlite3VdbeJumpHere(v, j1);
+sqlite3ExprCodeCopy(pParse, pIn->iMem, regPrev+1, pIn->nMem);
+sqlite3VdbeAddOp2(v, OP_Integer, 1, regPrev);
+}
+if( pParse->db->mallocFailed ) return 0;
+/* Suppress the the first OFFSET entries if there is an OFFSET clause
+*/
+codeOffset(v, p, iContinue);
+switch( pDest->eDest ){
+/* Store the result as data using a unique key.
+*/
+case SRT_Table:
+case SRT_EphemTab: {
+int r1 = sqlite3GetTempReg(pParse);
+int r2 = sqlite3GetTempReg(pParse);
+sqlite3VdbeAddOp3(v, OP_MakeRecord, pIn->iMem, pIn->nMem, r1);
+sqlite3VdbeAddOp2(v, OP_NewRowid, pDest->iParm, r2);
+sqlite3VdbeAddOp3(v, OP_Insert, pDest->iParm, r1, r2);
+sqlite3VdbeChangeP5(v, OPFLAG_APPEND);
+sqlite3ReleaseTempReg(pParse, r2);
+sqlite3ReleaseTempReg(pParse, r1);
+break;
+}
+#ifndef SQLITE_OMIT_SUBQUERY
+/* If we are creating a set for an "expr IN (SELECT ...)" construct,
+** then there should be a single item on the stack.  Write this
+** item into the set table with bogus data.
+*/
+case SRT_Set: {
+int r1;
+assert( pIn->nMem==1 );
+p->affinity =
+sqlite3CompareAffinity(p->pEList->a[0].pExpr, pDest->affinity);
+r1 = sqlite3GetTempReg(pParse);
+sqlite3VdbeAddOp4(v, OP_MakeRecord, pIn->iMem, 1, r1, &p->affinity, 1);
+sqlite3ExprCacheAffinityChange(pParse, pIn->iMem, 1);
+sqlite3VdbeAddOp2(v, OP_IdxInsert, pDest->iParm, r1);
+sqlite3ReleaseTempReg(pParse, r1);
+break;
+}
+#if 0  /* Never occurs on an ORDER BY query */
+/* If any row exist in the result set, record that fact and abort.
+*/
+case SRT_Exists: {
+sqlite3VdbeAddOp2(v, OP_Integer, 1, pDest->iParm);
+/* The LIMIT clause will terminate the loop for us */
+break;
+}
+#endif
+/* If this is a scalar select that is part of an expression, then
+** store the results in the appropriate memory cell and break out
+** of the scan loop.
+*/
+case SRT_Mem: {
+assert( pIn->nMem==1 );
+sqlite3ExprCodeMove(pParse, pIn->iMem, pDest->iParm, 1);
+/* The LIMIT clause will jump out of the loop for us */
+break;
+}
+#endif /* #ifndef SQLITE_OMIT_SUBQUERY */
+/* The results are stored in a sequence of registers
+** starting at pDest->iMem.  Then the co-routine yields.
+*/
+case SRT_Coroutine: {
+if( pDest->iMem==0 ){
+pDest->iMem = sqlite3GetTempRange(pParse, pIn->nMem);
+pDest->nMem = pIn->nMem;
+}
+sqlite3ExprCodeMove(pParse, pIn->iMem, pDest->iMem, pDest->nMem);
+sqlite3VdbeAddOp1(v, OP_Yield, pDest->iParm);
+break;
+}
+/* Results are stored in a sequence of registers.  Then the
+** OP_ResultRow opcode is used to cause sqlite3_step() to return
+** the next row of result.
+*/
+case SRT_Output: {
+sqlite3VdbeAddOp2(v, OP_ResultRow, pIn->iMem, pIn->nMem);
+sqlite3ExprCacheAffinityChange(pParse, pIn->iMem, pIn->nMem);
+break;
+}
+#if !defined(SQLITE_OMIT_TRIGGER)
+/* Discard the results.  This is used for SELECT statements inside
+** the body of a TRIGGER.  The purpose of such selects is to call
+** user-defined functions that have side effects.  We do not care
+** about the actual results of the select.
+*/
+default: {
+break;
+}
+#endif
+}
+/* Jump to the end of the loop if the LIMIT is reached.
+*/
+if( p->iLimit ){
+sqlite3VdbeAddOp2(v, OP_AddImm, p->iLimit, -1);
+sqlite3VdbeAddOp2(v, OP_IfZero, p->iLimit, iBreak);
+}
+/* Generate the subroutine return
+*/
+sqlite3VdbeResolveLabel(v, iContinue);
+sqlite3VdbeAddOp1(v, OP_Return, regReturn);
+return addr;
+}
+/*
+** Alternative compound select code generator for cases when there
+** is an ORDER BY clause.
+**
+** We assume a query of the following form:
+**
+**      <selectA>  <operator>  <selectB>  ORDER BY <orderbylist>
+**
+** <operator> is one of UNION ALL, UNION, EXCEPT, or INTERSECT.  The idea
+** is to code both <selectA> and <selectB> with the ORDER BY clause as
+** co-routines.  Then run the co-routines in parallel and merge the results
+** into the output.  In addition to the two coroutines (called selectA and
+** selectB) there are 7 subroutines:
+**
+**    outA:    Move the output of the selectA coroutine into the output
+**             of the compound query.
+**
+**    outB:    Move the output of the selectB coroutine into the output
+**             of the compound query.  (Only generated for UNION and
+**             UNION ALL.  EXCEPT and INSERTSECT never output a row that
+**             appears only in B.)
+**
+**    AltB:    Called when there is data from both coroutines and A<B.
+**
+**    AeqB:    Called when there is data from both coroutines and A==B.
+**
+**    AgtB:    Called when there is data from both coroutines and A>B.
+**
+**    EofA:    Called when data is exhausted from selectA.
+**
+**    EofB:    Called when data is exhausted from selectB.
+**
+** The implementation of the latter five subroutines depend on which
+** <operator> is used:
+**
+**
+**             UNION ALL         UNION            EXCEPT          INTERSECT
+**          -------------  -----------------  --------------  -----------------
+**   AltB:   outA, nextA      outA, nextA       outA, nextA         nextA
+**
+**   AeqB:   outA, nextA         nextA             nextA         outA, nextA
+**
+**   AgtB:   outB, nextB      outB, nextB          nextB            nextB
+**
+**   EofA:   outB, nextB      outB, nextB          halt             halt
+**
+**   EofB:   outA, nextA      outA, nextA       outA, nextA         halt
+**
+** In the AltB, AeqB, and AgtB subroutines, an EOF on A following nextA
+** causes an immediate jump to EofA and an EOF on B following nextB causes
+** an immediate jump to EofB.  Within EofA and EofB, and EOF on entry or
+** following nextX causes a jump to the end of the select processing.
+**
+** Duplicate removal in the UNION, EXCEPT, and INTERSECT cases is handled
+** within the output subroutine.  The regPrev register set holds the previously
+** output value.  A comparison is made against this value and the output
+** is skipped if the next results would be the same as the previous.
+**
+** The implementation plan is to implement the two coroutines and seven
+** subroutines first, then put the control logic at the bottom.  Like this:
+**
+**          goto Init
+**     coA: coroutine for left query (A)
+**     coB: coroutine for right query (B)
+**    outA: output one row of A
+**    outB: output one row of B (UNION and UNION ALL only)
+**    EofA: ...
+**    EofB: ...
+**    AltB: ...
+**    AeqB: ...
+**    AgtB: ...
+**    Init: initialize coroutine registers
+**          yield coA
+**          if eof(A) goto EofA
+**          yield coB
+**          if eof(B) goto EofB
+**    Cmpr: Compare A, B
+**          Jump AltB, AeqB, AgtB
+**     End: ...
+**
+** We call AltB, AeqB, AgtB, EofA, and EofB "subroutines" but they are not
+** actually called using Gosub and they do not Return.  EofA and EofB loop
+** until all data is exhausted then jump to the "end" labe.  AltB, AeqB,
+** and AgtB jump to either L2 or to one of EofA or EofB.
+*/
+#ifndef SQLITE_OMIT_COMPOUND_SELECT
+static int multiSelectOrderBy(
+Parse *pParse,        /* Parsing context */
+Select *p,            /* The right-most of SELECTs to be coded */
+SelectDest *pDest     /* What to do with query results */
+){
+int i, j;             /* Loop counters */
+Select *pPrior;       /* Another SELECT immediately to our left */
+Vdbe *v;              /* Generate code to this VDBE */
+SelectDest destA;     /* Destination for coroutine A */
+SelectDest destB;     /* Destination for coroutine B */
+int regAddrA;         /* Address register for select-A coroutine */
+int regEofA;          /* Flag to indicate when select-A is complete */
+int regAddrB;         /* Address register for select-B coroutine */
+int regEofB;          /* Flag to indicate when select-B is complete */
+int addrSelectA;      /* Address of the select-A coroutine */
+int addrSelectB;      /* Address of the select-B coroutine */
+int regOutA;          /* Address register for the output-A subroutine */
+int regOutB;          /* Address register for the output-B subroutine */
+int addrOutA;         /* Address of the output-A subroutine */
+int addrOutB;         /* Address of the output-B subroutine */
+int addrEofA;         /* Address of the select-A-exhausted subroutine */
+int addrEofB;         /* Address of the select-B-exhausted subroutine */
+int addrAltB;         /* Address of the A<B subroutine */
+int addrAeqB;         /* Address of the A==B subroutine */
+int addrAgtB;         /* Address of the A>B subroutine */
+int regLimitA;        /* Limit register for select-A */
+int regLimitB;        /* Limit register for select-A */
+int regPrev;          /* A range of registers to hold previous output */
+int savedLimit;       /* Saved value of p->iLimit */
+int savedOffset;      /* Saved value of p->iOffset */
+int labelCmpr;        /* Label for the start of the merge algorithm */
+int labelEnd;         /* Label for the end of the overall SELECT stmt */
+int j1;               /* Jump instructions that get retargetted */
+int op;               /* One of TK_ALL, TK_UNION, TK_EXCEPT, TK_INTERSECT */
+KeyInfo *pKeyDup = 0; /* Comparison information for duplicate removal */
+KeyInfo *pKeyMerge;   /* Comparison information for merging rows */
+sqlite3 *db;          /* Database connection */
+ExprList *pOrderBy;   /* The ORDER BY clause */
+int nOrderBy;         /* Number of terms in the ORDER BY clause */
+int *aPermute;        /* Mapping from ORDER BY terms to result set columns */
+assert( p->pOrderBy!=0 );
+assert( pKeyDup==0 ); /* "Managed" code needs this.  Ticket #3382. */
+db = pParse->db;
+v = pParse->pVdbe;
+if( v==0 ) return SQLITE_NOMEM;
+labelEnd = sqlite3VdbeMakeLabel(v);
+labelCmpr = sqlite3VdbeMakeLabel(v);
+/* Patch up the ORDER BY clause
+*/
+op = p->op;
+pPrior = p->pPrior;
+assert( pPrior->pOrderBy==0 );
+pOrderBy = p->pOrderBy;
+assert( pOrderBy );
+nOrderBy = pOrderBy->nExpr;
+/* For operators other than UNION ALL we have to make sure that
+** the ORDER BY clause covers every term of the result set.  Add
+** terms to the ORDER BY clause as necessary.
+*/
+if( op!=TK_ALL ){
+for(i=1; db->mallocFailed==0 && i<=p->pEList->nExpr; i++){
+struct ExprList_item *pItem;
+for(j=0, pItem=pOrderBy->a; j<nOrderBy; j++, pItem++){
+assert( pItem->iCol>0 );
+if( pItem->iCol==i ) break;
+}
+if( j==nOrderBy ){
+Expr *pNew = sqlite3PExpr(pParse, TK_INTEGER, 0, 0, 0);
+if( pNew==0 ) return SQLITE_NOMEM;
+pNew->flags |= EP_IntValue;
+pNew->iTable = i;
+pOrderBy = sqlite3ExprListAppend(pParse, pOrderBy, pNew, 0);
+pOrderBy->a[nOrderBy++].iCol = i;
+}
+}
+}
+/* Compute the comparison permutation and keyinfo that is used with
+** the permutation in order to comparisons to determine if the next
+** row of results comes from selectA or selectB.  Also add explicit
+** collations to the ORDER BY clause terms so that when the subqueries
+** to the right and the left are evaluated, they use the correct
+** collation.
+*/
+aPermute = sqlite3DbMallocRaw(db, sizeof(int)*nOrderBy);
+if( aPermute ){
+struct ExprList_item *pItem;
+for(i=0, pItem=pOrderBy->a; i<nOrderBy; i++, pItem++){
+assert( pItem->iCol>0  && pItem->iCol<=p->pEList->nExpr );
+aPermute[i] = pItem->iCol - 1;
+}
+pKeyMerge =
+sqlite3DbMallocRaw(db, sizeof(*pKeyMerge)+nOrderBy*(sizeof(CollSeq*)+1));
+if( pKeyMerge ){
+pKeyMerge->aSortOrder = (u8*)&pKeyMerge->aColl[nOrderBy];
+pKeyMerge->nField = nOrderBy;
+pKeyMerge->enc = ENC(db);
+for(i=0; i<nOrderBy; i++){
+CollSeq *pColl;
+Expr *pTerm = pOrderBy->a[i].pExpr;
+if( pTerm->flags & EP_ExpCollate ){
+pColl = pTerm->pColl;
+}else{
+pColl = multiSelectCollSeq(pParse, p, aPermute[i]);
+pTerm->flags |= EP_ExpCollate;
+pTerm->pColl = pColl;
+}
+pKeyMerge->aColl[i] = pColl;
+pKeyMerge->aSortOrder[i] = pOrderBy->a[i].sortOrder;
+}
+}
+}else{
+pKeyMerge = 0;
+}
+/* Reattach the ORDER BY clause to the query.
+*/
+p->pOrderBy = pOrderBy;
+pPrior->pOrderBy = sqlite3ExprListDup(pParse->db, pOrderBy);
+/* Allocate a range of temporary registers and the KeyInfo needed
+** for the logic that removes duplicate result rows when the
+** operator is UNION, EXCEPT, or INTERSECT (but not UNION ALL).
+*/
+if( op==TK_ALL ){
+regPrev = 0;
+}else{
+int nExpr = p->pEList->nExpr;
+assert( nOrderBy>=nExpr );
+regPrev = sqlite3GetTempRange(pParse, nExpr+1);
+sqlite3VdbeAddOp2(v, OP_Integer, 0, regPrev);
+pKeyDup = sqlite3DbMallocZero(db,
+sizeof(*pKeyDup) + nExpr*(sizeof(CollSeq*)+1) );
+if( pKeyDup ){
+pKeyDup->aSortOrder = (u8*)&pKeyDup->aColl[nExpr];
+pKeyDup->nField = nExpr;
+pKeyDup->enc = ENC(db);
+for(i=0; i<nExpr; i++){
+pKeyDup->aColl[i] = multiSelectCollSeq(pParse, p, i);
+pKeyDup->aSortOrder[i] = 0;
+}
+}
+}
+/* Separate the left and the right query from one another
+*/
+p->pPrior = 0;
+pPrior->pRightmost = 0;
+sqlite3ResolveOrderGroupBy(pParse, p, p->pOrderBy, "ORDER");
+if( pPrior->pPrior==0 ){
+sqlite3ResolveOrderGroupBy(pParse, pPrior, pPrior->pOrderBy, "ORDER");
+}
+/* Compute the limit registers */
+computeLimitRegisters(pParse, p, labelEnd);
+if( p->iLimit && op==TK_ALL ){
+regLimitA = ++pParse->nMem;
+regLimitB = ++pParse->nMem;
+sqlite3VdbeAddOp2(v, OP_Copy, p->iOffset ? p->iOffset+1 : p->iLimit,
+regLimitA);
+sqlite3VdbeAddOp2(v, OP_Copy, regLimitA, regLimitB);
+}else{
+regLimitA = regLimitB = 0;
+}
+sqlite3ExprDelete(db, p->pLimit);
+p->pLimit = 0;
+sqlite3ExprDelete(db, p->pOffset);
+p->pOffset = 0;
+regAddrA = ++pParse->nMem;
+regEofA = ++pParse->nMem;
+regAddrB = ++pParse->nMem;
+regEofB = ++pParse->nMem;
+regOutA = ++pParse->nMem;
+regOutB = ++pParse->nMem;
+sqlite3SelectDestInit(&destA, SRT_Coroutine, regAddrA);
+sqlite3SelectDestInit(&destB, SRT_Coroutine, regAddrB);
+/* Jump past the various subroutines and coroutines to the main
+** merge loop
+*/
+j1 = sqlite3VdbeAddOp0(v, OP_Goto);
+addrSelectA = sqlite3VdbeCurrentAddr(v);
+/* Generate a coroutine to evaluate the SELECT statement to the
+** left of the compound operator - the "A" select.
+*/
+VdbeNoopComment((v, "Begin coroutine for left SELECT"));
+pPrior->iLimit = regLimitA;
+sqlite3Select(pParse, pPrior, &destA);
+sqlite3VdbeAddOp2(v, OP_Integer, 1, regEofA);
+sqlite3VdbeAddOp1(v, OP_Yield, regAddrA);
+VdbeNoopComment((v, "End coroutine for left SELECT"));
+/* Generate a coroutine to evaluate the SELECT statement on
+** the right - the "B" select
+*/
+addrSelectB = sqlite3VdbeCurrentAddr(v);
+VdbeNoopComment((v, "Begin coroutine for right SELECT"));
+savedLimit = p->iLimit;
+savedOffset = p->iOffset;
+p->iLimit = regLimitB;
+p->iOffset = 0;
+sqlite3Select(pParse, p, &destB);
+p->iLimit = savedLimit;
+p->iOffset = savedOffset;
+sqlite3VdbeAddOp2(v, OP_Integer, 1, regEofB);
+sqlite3VdbeAddOp1(v, OP_Yield, regAddrB);
+VdbeNoopComment((v, "End coroutine for right SELECT"));
+/* Generate a subroutine that outputs the current row of the A
+** select as the next output row of the compound select.
+*/
+VdbeNoopComment((v, "Output routine for A"));
+addrOutA = generateOutputSubroutine(pParse,
+p, &destA, pDest, regOutA,
+regPrev, pKeyDup, P4_KEYINFO_HANDOFF, labelEnd);
+/* Generate a subroutine that outputs the current row of the B
+** select as the next output row of the compound select.
+*/
+if( op==TK_ALL || op==TK_UNION ){
+VdbeNoopComment((v, "Output routine for B"));
+addrOutB = generateOutputSubroutine(pParse,
+p, &destB, pDest, regOutB,
+regPrev, pKeyDup, P4_KEYINFO_STATIC, labelEnd);
+}
+/* Generate a subroutine to run when the results from select A
+** are exhausted and only data in select B remains.
+*/
+VdbeNoopComment((v, "eof-A subroutine"));
+if( op==TK_EXCEPT || op==TK_INTERSECT ){
+addrEofA = sqlite3VdbeAddOp2(v, OP_Goto, 0, labelEnd);
+}else{
+addrEofA = sqlite3VdbeAddOp2(v, OP_If, regEofB, labelEnd);
+sqlite3VdbeAddOp2(v, OP_Gosub, regOutB, addrOutB);
+sqlite3VdbeAddOp1(v, OP_Yield, regAddrB);
+sqlite3VdbeAddOp2(v, OP_Goto, 0, addrEofA);
+}
+/* Generate a subroutine to run when the results from select B
+** are exhausted and only data in select A remains.
+*/
+if( op==TK_INTERSECT ){
+addrEofB = addrEofA;
+}else{
+VdbeNoopComment((v, "eof-B subroutine"));
+addrEofB = sqlite3VdbeAddOp2(v, OP_If, regEofA, labelEnd);
+sqlite3VdbeAddOp2(v, OP_Gosub, regOutA, addrOutA);
+sqlite3VdbeAddOp1(v, OP_Yield, regAddrA);
+sqlite3VdbeAddOp2(v, OP_Goto, 0, addrEofB);
+}
+/* Generate code to handle the case of A<B
+*/
+VdbeNoopComment((v, "A-lt-B subroutine"));
+addrAltB = sqlite3VdbeAddOp2(v, OP_Gosub, regOutA, addrOutA);
+sqlite3VdbeAddOp1(v, OP_Yield, regAddrA);
+sqlite3VdbeAddOp2(v, OP_If, regEofA, addrEofA);
+sqlite3VdbeAddOp2(v, OP_Goto, 0, labelCmpr);
+/* Generate code to handle the case of A==B
+*/
+if( op==TK_ALL ){
+addrAeqB = addrAltB;
+}else if( op==TK_INTERSECT ){
+addrAeqB = addrAltB;
+addrAltB++;
+}else{
+VdbeNoopComment((v, "A-eq-B subroutine"));
+addrAeqB =
+sqlite3VdbeAddOp1(v, OP_Yield, regAddrA);
+sqlite3VdbeAddOp2(v, OP_If, regEofA, addrEofA);
+sqlite3VdbeAddOp2(v, OP_Goto, 0, labelCmpr);
+}
+/* Generate code to handle the case of A>B
+*/
+VdbeNoopComment((v, "A-gt-B subroutine"));
+addrAgtB = sqlite3VdbeCurrentAddr(v);
+if( op==TK_ALL || op==TK_UNION ){
+sqlite3VdbeAddOp2(v, OP_Gosub, regOutB, addrOutB);
+}
+sqlite3VdbeAddOp1(v, OP_Yield, regAddrB);
+sqlite3VdbeAddOp2(v, OP_If, regEofB, addrEofB);
+sqlite3VdbeAddOp2(v, OP_Goto, 0, labelCmpr);
+/* This code runs once to initialize everything.
+*/
+sqlite3VdbeJumpHere(v, j1);
+sqlite3VdbeAddOp2(v, OP_Integer, 0, regEofA);
+sqlite3VdbeAddOp2(v, OP_Integer, 0, regEofB);
+sqlite3VdbeAddOp2(v, OP_Gosub, regAddrA, addrSelectA);
+sqlite3VdbeAddOp2(v, OP_Gosub, regAddrB, addrSelectB);
+sqlite3VdbeAddOp2(v, OP_If, regEofA, addrEofA);
+sqlite3VdbeAddOp2(v, OP_If, regEofB, addrEofB);
+/* Implement the main merge loop
+*/
+sqlite3VdbeResolveLabel(v, labelCmpr);
+sqlite3VdbeAddOp4(v, OP_Permutation, 0, 0, 0, (char*)aPermute, P4_INTARRAY);
+sqlite3VdbeAddOp4(v, OP_Compare, destA.iMem, destB.iMem, nOrderBy,
+(char*)pKeyMerge, P4_KEYINFO_HANDOFF);
+sqlite3VdbeAddOp3(v, OP_Jump, addrAltB, addrAeqB, addrAgtB);
+/* Release temporary registers
+*/
+if( regPrev ){
+sqlite3ReleaseTempRange(pParse, regPrev, nOrderBy+1);
+}
+/* Jump to the this point in order to terminate the query.
+*/
+sqlite3VdbeResolveLabel(v, labelEnd);
+/* Set the number of output columns
+*/
+if( pDest->eDest==SRT_Output ){
+Select *pFirst = pPrior;
+while( pFirst->pPrior ) pFirst = pFirst->pPrior;
+generateColumnNames(pParse, 0, pFirst->pEList);
+}
+/* Reassembly the compound query so that it will be freed correctly
+** by the calling function */
+if( p->pPrior ){
+sqlite3SelectDelete(db, p->pPrior);
+}
+p->pPrior = pPrior;
+/*** TBD:  Insert subroutine calls to close cursors on incomplete
+**** subqueries ****/
+return SQLITE_OK;
+}
+#endif
+#if !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW)
+/* Forward Declarations */
+static void substExprList(sqlite3*, ExprList*, int, ExprList*);
+static void substSelect(sqlite3*, Select *, int, ExprList *);
+/*
+** Scan through the expression pExpr.  Replace every reference to
+** a column in table number iTable with a copy of the iColumn-th
+** entry in pEList.  (But leave references to the ROWID column
+** unchanged.)
+**
+** This routine is part of the flattening procedure.  A subquery
+** whose result set is defined by pEList appears as entry in the
+** FROM clause of a SELECT such that the VDBE cursor assigned to that
+** FORM clause entry is iTable.  This routine make the necessary
+** changes to pExpr so that it refers directly to the source table
+** of the subquery rather the result set of the subquery.
+*/
+static void substExpr(
+sqlite3 *db,        /* Report malloc errors to this connection */
+Expr *pExpr,        /* Expr in which substitution occurs */
+int iTable,         /* Table to be substituted */
+ExprList *pEList    /* Substitute expressions */
+){
+if( pExpr==0 ) return;
+if( pExpr->op==TK_COLUMN && pExpr->iTable==iTable ){
+if( pExpr->iColumn<0 ){
+pExpr->op = TK_NULL;
+}else{
+Expr *pNew;
+assert( pEList!=0 && pExpr->iColumn<pEList->nExpr );
+assert( pExpr->pLeft==0 && pExpr->pRight==0 && pExpr->pList==0 );
+pNew = pEList->a[pExpr->iColumn].pExpr;
+assert( pNew!=0 );
+pExpr->op = pNew->op;
+assert( pExpr->pLeft==0 );
+pExpr->pLeft = sqlite3ExprDup(db, pNew->pLeft);
+assert( pExpr->pRight==0 );
+pExpr->pRight = sqlite3ExprDup(db, pNew->pRight);
+assert( pExpr->pList==0 );
+pExpr->pList = sqlite3ExprListDup(db, pNew->pList);
+pExpr->iTable = pNew->iTable;
+pExpr->pTab = pNew->pTab;
+pExpr->iColumn = pNew->iColumn;
+pExpr->iAgg = pNew->iAgg;
+sqlite3TokenCopy(db, &pExpr->token, &pNew->token);
+sqlite3TokenCopy(db, &pExpr->span, &pNew->span);
+pExpr->pSelect = sqlite3SelectDup(db, pNew->pSelect);
+pExpr->flags = pNew->flags;
+}
+}else{
+substExpr(db, pExpr->pLeft, iTable, pEList);
+substExpr(db, pExpr->pRight, iTable, pEList);
+substSelect(db, pExpr->pSelect, iTable, pEList);
+substExprList(db, pExpr->pList, iTable, pEList);
+}
+}
+static void substExprList(
+sqlite3 *db,         /* Report malloc errors here */
+ExprList *pList,     /* List to scan and in which to make substitutes */
+int iTable,          /* Table to be substituted */
+ExprList *pEList     /* Substitute values */
+){
+int i;
+if( pList==0 ) return;
+for(i=0; i<pList->nExpr; i++){
+substExpr(db, pList->a[i].pExpr, iTable, pEList);
+}
+}
+static void substSelect(
+sqlite3 *db,         /* Report malloc errors here */
+Select *p,           /* SELECT statement in which to make substitutions */
+int iTable,          /* Table to be replaced */
+ExprList *pEList     /* Substitute values */
+){
+SrcList *pSrc;
+struct SrcList_item *pItem;
+int i;
+if( !p ) return;
+substExprList(db, p->pEList, iTable, pEList);
+substExprList(db, p->pGroupBy, iTable, pEList);
+substExprList(db, p->pOrderBy, iTable, pEList);
+substExpr(db, p->pHaving, iTable, pEList);
+substExpr(db, p->pWhere, iTable, pEList);
+substSelect(db, p->pPrior, iTable, pEList);
+pSrc = p->pSrc;
+if( pSrc ){
+for(i=pSrc->nSrc, pItem=pSrc->a; i>0; i--, pItem++){
+substSelect(db, pItem->pSelect, iTable, pEList);
+}
+}
+}
+#endif /* !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW) */
+#if !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW)
+/*
+** This routine attempts to flatten subqueries in order to speed
+** execution.  It returns 1 if it makes changes and 0 if no flattening
+** occurs.
+**
+** To understand the concept of flattening, consider the following
+** query:
+**
+**     SELECT a FROM (SELECT x+y AS a FROM t1 WHERE z<100) WHERE a>5
+**
+** The default way of implementing this query is to execute the
+** subquery first and store the results in a temporary table, then
+** run the outer query on that temporary table.  This requires two
+** passes over the data.  Furthermore, because the temporary table
+** has no indices, the WHERE clause on the outer query cannot be
+** optimized.
+**
+** This routine attempts to rewrite queries such as the above into
+** a single flat select, like this:
+**
+**     SELECT x+y AS a FROM t1 WHERE z<100 AND a>5
+**
+** The code generated for this simpification gives the same result
+** but only has to scan the data once.  And because indices might
+** exist on the table t1, a complete scan of the data might be
+** avoided.
+**
+** Flattening is only attempted if all of the following are true:
+**
+**   (1)  The subquery and the outer query do not both use aggregates.
+**
+**   (2)  The subquery is not an aggregate or the outer query is not a join.
+**
+**   (3)  The subquery is not the right operand of a left outer join
+**        (Originally ticket #306.  Strenghtened by ticket #3300)
+**
+**   (4)  The subquery is not DISTINCT or the outer query is not a join.
+**
+**   (5)  The subquery is not DISTINCT or the outer query does not use
+**        aggregates.
+**
+**   (6)  The subquery does not use aggregates or the outer query is not
+**        DISTINCT.
+**
+**   (7)  The subquery has a FROM clause.
+**
+**   (8)  The subquery does not use LIMIT or the outer query is not a join.
+**
+**   (9)  The subquery does not use LIMIT or the outer query does not use
+**        aggregates.
+**
+**  (10)  The subquery does not use aggregates or the outer query does not
+**        use LIMIT.
+**
+**  (11)  The subquery and the outer query do not both have ORDER BY clauses.
+**
+**  (12)  Not implemented.  Subsumed into restriction (3).  Was previously
+**        a separate restriction deriving from ticket #350.
+**
+**  (13)  The subquery and outer query do not both use LIMIT
+**
+**  (14)  The subquery does not use OFFSET
+**
+**  (15)  The outer query is not part of a compound select or the
+**        subquery does not have both an ORDER BY and a LIMIT clause.
+**        (See ticket #2339)
+**
+**  (16)  The outer query is not an aggregate or the subquery does
+**        not contain ORDER BY.  (Ticket #2942)  This used to not matter
+**        until we introduced the group_concat() function.
+**
+**  (17)  The sub-query is not a compound select, or it is a UNION ALL
+**        compound clause made up entirely of non-aggregate queries, and
+**        the parent query:
+**
+**          * is not itself part of a compound select,
+**          * is not an aggregate or DISTINCT query, and
+**          * has no other tables or sub-selects in the FROM clause.
+**
+**        The parent and sub-query may contain WHERE clauses. Subject to
+**        rules (11), (13) and (14), they may also contain ORDER BY,
+**        LIMIT and OFFSET clauses.
+**
+**  (18)  If the sub-query is a compound select, then all terms of the
+**        ORDER by clause of the parent must be simple references to
+**        columns of the sub-query.
+**
+**  (19)  The subquery does not use LIMIT or the outer query does not
+**        have a WHERE clause.
+**
+** In this routine, the "p" parameter is a pointer to the outer query.
+** The subquery is p->pSrc->a[iFrom].  isAgg is true if the outer query
+** uses aggregates and subqueryIsAgg is true if the subquery uses aggregates.
+**
+** If flattening is not attempted, this routine is a no-op and returns 0.
+** If flattening is attempted this routine returns 1.
+**
+** All of the expression analysis must occur on both the outer query and
+** the subquery before this routine runs.
+*/
+static int flattenSubquery(
+Parse *pParse,       /* Parsing context */
+Select *p,           /* The parent or outer SELECT statement */
+int iFrom,           /* Index in p->pSrc->a[] of the inner subquery */
+int isAgg,           /* True if outer SELECT uses aggregate functions */
+int subqueryIsAgg    /* True if the subquery uses aggregate functions */
+){
+const char *zSavedAuthContext = pParse->zAuthContext;
+Select *pParent;
+Select *pSub;       /* The inner query or "subquery" */
+Select *pSub1;      /* Pointer to the rightmost select in sub-query */
+SrcList *pSrc;      /* The FROM clause of the outer query */
+SrcList *pSubSrc;   /* The FROM clause of the subquery */
+ExprList *pList;    /* The result set of the outer query */
+int iParent;        /* VDBE cursor number of the pSub result set temp table */
+int i;              /* Loop counter */
+Expr *pWhere;                    /* The WHERE clause */
+struct SrcList_item *pSubitem;   /* The subquery */
+sqlite3 *db = pParse->db;
+/* Check to see if flattening is permitted.  Return 0 if not.
+*/
+if( p==0 ) return 0;
+pSrc = p->pSrc;
+assert( pSrc && iFrom>=0 && iFrom<pSrc->nSrc );
+pSubitem = &pSrc->a[iFrom];
+iParent = pSubitem->iCursor;
+pSub = pSubitem->pSelect;
+assert( pSub!=0 );
+if( isAgg && subqueryIsAgg ) return 0;                 /* Restriction (1)  */
+if( subqueryIsAgg && pSrc->nSrc>1 ) return 0;          /* Restriction (2)  */
+pSubSrc = pSub->pSrc;
+assert( pSubSrc );
+/* Prior to version 3.1.2, when LIMIT and OFFSET had to be simple constants,
+** not arbitrary expresssions, we allowed some combining of LIMIT and OFFSET
+** because they could be computed at compile-time.  But when LIMIT and OFFSET
+** became arbitrary expressions, we were forced to add restrictions (13)
+** and (14). */
+if( pSub->pLimit && p->pLimit ) return 0;              /* Restriction (13) */
+if( pSub->pOffset ) return 0;                          /* Restriction (14) */
+if( p->pRightmost && pSub->pLimit && pSub->pOrderBy ){
+return 0;                                            /* Restriction (15) */
+}
+if( pSubSrc->nSrc==0 ) return 0;                       /* Restriction (7)  */
+if( ((pSub->selFlags & SF_Distinct)!=0 || pSub->pLimit)
+&& (pSrc->nSrc>1 || isAgg) ){          /* Restrictions (4)(5)(8)(9) */
+return 0;
+}
+if( (p->selFlags & SF_Distinct)!=0 && subqueryIsAgg ){
+return 0;         /* Restriction (6)  */
+}
+if( p->pOrderBy && pSub->pOrderBy ){
+return 0;                                           /* Restriction (11) */
+}
+if( isAgg && pSub->pOrderBy ) return 0;                /* Restriction (16) */
+if( pSub->pLimit && p->pWhere ) return 0;              /* Restriction (19) */
+/* OBSOLETE COMMENT 1:
+** Restriction 3:  If the subquery is a join, make sure the subquery is
+** not used as the right operand of an outer join.  Examples of why this
+** is not allowed:
+**
+**         t1 LEFT OUTER JOIN (t2 JOIN t3)
+**
+** If we flatten the above, we would get
+**
+**         (t1 LEFT OUTER JOIN t2) JOIN t3
+**
+** which is not at all the same thing.
+**
+** OBSOLETE COMMENT 2:
+** Restriction 12:  If the subquery is the right operand of a left outer
+** join, make sure the subquery has no WHERE clause.
+** An examples of why this is not allowed:
+**
+**         t1 LEFT OUTER JOIN (SELECT * FROM t2 WHERE t2.x>0)
+**
+** If we flatten the above, we would get
+**
+**         (t1 LEFT OUTER JOIN t2) WHERE t2.x>0
+**
+** But the t2.x>0 test will always fail on a NULL row of t2, which
+** effectively converts the OUTER JOIN into an INNER JOIN.
+**
+** THIS OVERRIDES OBSOLETE COMMENTS 1 AND 2 ABOVE:
+** Ticket #3300 shows that flattening the right term of a LEFT JOIN
+** is fraught with danger.  Best to avoid the whole thing.  If the
+** subquery is the right term of a LEFT JOIN, then do not flatten.
+*/
+if( (pSubitem->jointype & JT_OUTER)!=0 ){
+return 0;
+}
+/* Restriction 17: If the sub-query is a compound SELECT, then it must
+** use only the UNION ALL operator. And none of the simple select queries
+** that make up the compound SELECT are allowed to be aggregate or distinct
+** queries.
+*/
+if( pSub->pPrior ){
+if( p->pPrior || isAgg || (p->selFlags & SF_Distinct)!=0 || pSrc->nSrc!=1 ){
+return 0;
+}
+for(pSub1=pSub; pSub1; pSub1=pSub1->pPrior){
+if( (pSub1->selFlags & (SF_Distinct|SF_Aggregate))!=0
+|| (pSub1->pPrior && pSub1->op!=TK_ALL)
+|| !pSub1->pSrc || pSub1->pSrc->nSrc!=1
+){
+return 0;
+}
+}
+/* Restriction 18. */
+if( p->pOrderBy ){
+int ii;
+for(ii=0; ii<p->pOrderBy->nExpr; ii++){
+if( p->pOrderBy->a[ii].iCol==0 ) return 0;
+}
+}
+}
+/***** If we reach this point, flattening is permitted. *****/
+/* Authorize the subquery */
+pParse->zAuthContext = pSubitem->zName;
+sqlite3AuthCheck(pParse, SQLITE_SELECT, 0, 0, 0);
+pParse->zAuthContext = zSavedAuthContext;
+/* If the sub-query is a compound SELECT statement, then (by restrictions
+** 17 and 18 above) it must be a UNION ALL and the parent query must
+** be of the form:
+**
+**     SELECT <expr-list> FROM (<sub-query>) <where-clause>
+**
+** followed by any ORDER BY, LIMIT and/or OFFSET clauses. This block
+** creates N copies of the parent query without any ORDER BY, LIMIT or
+** OFFSET clauses and joins them to the left-hand-side of the original
+** using UNION ALL operators. In this case N is the number of simple
+** select statements in the compound sub-query.
+*/
+for(pSub=pSub->pPrior; pSub; pSub=pSub->pPrior){
+Select *pNew;
+ExprList *pOrderBy = p->pOrderBy;
+Expr *pLimit = p->pLimit;
+Expr *pOffset = p->pOffset;
+Select *pPrior = p->pPrior;
+p->pOrderBy = 0;
+p->pSrc = 0;
+p->pPrior = 0;
+p->pLimit = 0;
+pNew = sqlite3SelectDup(db, p);
+pNew->pPrior = pPrior;
+p->pPrior = pNew;
+p->pOrderBy = pOrderBy;
+p->op = TK_ALL;
+p->pSrc = pSrc;
+p->pLimit = pLimit;
+p->pOffset = pOffset;
+p->pRightmost = 0;
+pNew->pRightmost = 0;
+}
+/* Begin flattening the iFrom-th entry of the FROM clause
+** in the outer query.
+*/
+pSub = pSub1 = pSubitem->pSelect;
+for(pParent=p; pParent; pParent=pParent->pPrior, pSub=pSub->pPrior){
+int nSubSrc = pSubSrc->nSrc;
+int jointype = 0;
+pSubSrc = pSub->pSrc;
+pSrc = pParent->pSrc;
+/* Move all of the FROM elements of the subquery into the
+** the FROM clause of the outer query.  Before doing this, remember
+** the cursor number for the original outer query FROM element in
+** iParent.  The iParent cursor will never be used.  Subsequent code
+** will scan expressions looking for iParent references and replace
+** those references with expressions that resolve to the subquery FROM
+** elements we are now copying in.
+*/
+if( pSrc ){
+Table *pTabToDel;
+pSubitem = &pSrc->a[iFrom];
+nSubSrc = pSubSrc->nSrc;
+jointype = pSubitem->jointype;
+sqlite3DbFree(db, pSubitem->zDatabase);
+sqlite3DbFree(db, pSubitem->zName);
+sqlite3DbFree(db, pSubitem->zAlias);
+pSubitem->zDatabase = 0;
+pSubitem->zName = 0;
+pSubitem->zAlias = 0;
+/* If the FROM element is a subquery, defer deleting the Table
+** object associated with that subquery until code generation is
+** complete, since there may still exist Expr.pTab entires that
+** refer to the subquery even after flattening.  Ticket #3346.
+*/
+if( (pTabToDel = pSubitem->pTab)!=0 ){
+if( pTabToDel->nRef==1 ){
+pTabToDel->pNextZombie = pParse->pZombieTab;
+pParse->pZombieTab = pTabToDel;
+}else{
+pTabToDel->nRef--;
+}
+}
+pSubitem->pTab = 0;
+}
+if( nSubSrc!=1 || !pSrc ){
+int extra = nSubSrc - 1;
+for(i=(pSrc?1:0); i<nSubSrc; i++){
+pSrc = sqlite3SrcListAppend(db, pSrc, 0, 0);
+if( pSrc==0 ){
+pParent->pSrc = 0;
+return 1;
+}
+}
+pParent->pSrc = pSrc;
+for(i=pSrc->nSrc-1; i-extra>=iFrom; i--){
+pSrc->a[i] = pSrc->a[i-extra];
+}
+}
+for(i=0; i<nSubSrc; i++){
+pSrc->a[i+iFrom] = pSubSrc->a[i];
+memset(&pSubSrc->a[i], 0, sizeof(pSubSrc->a[i]));
+}
+pSrc->a[iFrom].jointype = jointype;
+/* Now begin substituting subquery result set expressions for
+** references to the iParent in the outer query.
+**
+** Example:
+**
+**   SELECT a+5, b*10 FROM (SELECT x*3 AS a, y+10 AS b FROM t1) WHERE a>b;
+**   \                     \_____________ subquery __________/          /
+**    \_____________________ outer query ______________________________/
+**
+** We look at every expression in the outer query and every place we see
+** "a" we substitute "x*3" and every place we see "b" we substitute "y+10".
+*/
+pList = pParent->pEList;
+for(i=0; i<pList->nExpr; i++){
+Expr *pExpr;
+if( pList->a[i].zName==0 && (pExpr = pList->a[i].pExpr)->span.z!=0 ){
+pList->a[i].zName =
+sqlite3DbStrNDup(db, (char*)pExpr->span.z, pExpr->span.n);
+}
+}
+substExprList(db, pParent->pEList, iParent, pSub->pEList);
+if( isAgg ){
+substExprList(db, pParent->pGroupBy, iParent, pSub->pEList);
+substExpr(db, pParent->pHaving, iParent, pSub->pEList);
+}
+if( pSub->pOrderBy ){
+assert( pParent->pOrderBy==0 );
+pParent->pOrderBy = pSub->pOrderBy;
+pSub->pOrderBy = 0;
+}else if( pParent->pOrderBy ){
+substExprList(db, pParent->pOrderBy, iParent, pSub->pEList);
+}
+if( pSub->pWhere ){
+pWhere = sqlite3ExprDup(db, pSub->pWhere);
+}else{
+pWhere = 0;
+}
+if( subqueryIsAgg ){
+assert( pParent->pHaving==0 );
+pParent->pHaving = pParent->pWhere;
+pParent->pWhere = pWhere;
+substExpr(db, pParent->pHaving, iParent, pSub->pEList);
+pParent->pHaving = sqlite3ExprAnd(db, pParent->pHaving,
+sqlite3ExprDup(db, pSub->pHaving));
+assert( pParent->pGroupBy==0 );
+pParent->pGroupBy = sqlite3ExprListDup(db, pSub->pGroupBy);
+}else{
+substExpr(db, pParent->pWhere, iParent, pSub->pEList);
+pParent->pWhere = sqlite3ExprAnd(db, pParent->pWhere, pWhere);
+}
+/* The flattened query is distinct if either the inner or the
+** outer query is distinct.
+*/
+pParent->selFlags |= pSub->selFlags & SF_Distinct;
+/*
+** SELECT ... FROM (SELECT ... LIMIT a OFFSET b) LIMIT x OFFSET y;
+**
+** One is tempted to try to add a and b to combine the limits.  But this
+** does not work if either limit is negative.
+*/
+if( pSub->pLimit ){
+pParent->pLimit = pSub->pLimit;
+pSub->pLimit = 0;
+}
+}
+/* Finially, delete what is left of the subquery and return
+** success.
+*/
+sqlite3SelectDelete(db, pSub1);
+return 1;
+}
+#endif /* !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW) */
+/*
+** Analyze the SELECT statement passed as an argument to see if it
+** is a min() or max() query. Return WHERE_ORDERBY_MIN or WHERE_ORDERBY_MAX if
+** it is, or 0 otherwise. At present, a query is considered to be
+** a min()/max() query if:
+**
+**   1. There is a single object in the FROM clause.
+**
+**   2. There is a single expression in the result set, and it is
+**      either min(x) or max(x), where x is a column reference.
+*/
+static int minMaxQuery(Parse *pParse, Select *p){
+Expr *pExpr;
+ExprList *pEList = p->pEList;
+if( pEList->nExpr!=1 ) return WHERE_ORDERBY_NORMAL;
+pExpr = pEList->a[0].pExpr;
+pEList = pExpr->pList;
+if( pExpr->op!=TK_AGG_FUNCTION || pEList==0 || pEList->nExpr!=1 ) return 0;
+if( pEList->a[0].pExpr->op!=TK_AGG_COLUMN ) return WHERE_ORDERBY_NORMAL;
+if( pExpr->token.n!=3 ) return WHERE_ORDERBY_NORMAL;
+if( sqlite3StrNICmp((char*)pExpr->token.z,"min",3)==0 ){
+return WHERE_ORDERBY_MIN;
+}else if( sqlite3StrNICmp((char*)pExpr->token.z,"max",3)==0 ){
+return WHERE_ORDERBY_MAX;
+}
+return WHERE_ORDERBY_NORMAL;
+}
+/*
+** This routine is a Walker callback for "expanding" a SELECT statement.
+** "Expanding" means to do the following:
+**
+**    (1)  Make sure VDBE cursor numbers have been assigned to every
+**         element of the FROM clause.
+**
+**    (2)  Fill in the pTabList->a[].pTab fields in the SrcList that
+**         defines FROM clause.  When views appear in the FROM clause,
+**         fill pTabList->a[].pSelect with a copy of the SELECT statement
+**         that implements the view.  A copy is made of the view's SELECT
+**         statement so that we can freely modify or delete that statement
+**         without worrying about messing up the presistent representation
+**         of the view.
+**
+**    (3)  Add terms to the WHERE clause to accomodate the NATURAL keyword
+**         on joins and the ON and USING clause of joins.
+**
+**    (4)  Scan the list of columns in the result set (pEList) looking
+**         for instances of the "*" operator or the TABLE.* operator.
+**         If found, expand each "*" to be every column in every table
+**         and TABLE.* to be every column in TABLE.
+**
+*/
+static int selectExpander(Walker *pWalker, Select *p){
+Parse *pParse = pWalker->pParse;
+int i, j, k;
+SrcList *pTabList;
+ExprList *pEList;
+struct SrcList_item *pFrom;
+sqlite3 *db = pParse->db;
+if( db->mallocFailed  ){
+return WRC_Abort;
+}
+if( p->pSrc==0 || (p->selFlags & SF_Expanded)!=0 ){
+return WRC_Prune;
+}
+p->selFlags |= SF_Expanded;
+pTabList = p->pSrc;
+pEList = p->pEList;
+/* Make sure cursor numbers have been assigned to all entries in
+** the FROM clause of the SELECT statement.
+*/
+sqlite3SrcListAssignCursors(pParse, pTabList);
+/* Look up every table named in the FROM clause of the select.  If
+** an entry of the FROM clause is a subquery instead of a table or view,
+** then create a transient table structure to describe the subquery.
+*/
+for(i=0, pFrom=pTabList->a; i<pTabList->nSrc; i++, pFrom++){
+Table *pTab;
+if( pFrom->pTab!=0 ){
+/* This statement has already been prepared.  There is no need
+** to go further. */
+assert( i==0 );
+return WRC_Prune;
+}
+if( pFrom->zName==0 ){
+#ifndef SQLITE_OMIT_SUBQUERY
+Select *pSel = pFrom->pSelect;
+/* A sub-query in the FROM clause of a SELECT */
+assert( pSel!=0 );
+assert( pFrom->pTab==0 );
+sqlite3WalkSelect(pWalker, pSel);
+pFrom->pTab = pTab = sqlite3DbMallocZero(db, sizeof(Table));
+if( pTab==0 ) return WRC_Abort;
+pTab->db = db;
+pTab->nRef = 1;
+pTab->zName = sqlite3MPrintf(db, "sqlite_subquery_%p_", (void*)pTab);
+while( pSel->pPrior ){ pSel = pSel->pPrior; }
+selectColumnsFromExprList(pParse, pSel->pEList, &pTab->nCol, &pTab->aCol);
+pTab->iPKey = -1;
+pTab->tabFlags |= TF_Ephemeral;
+#endif
+}else{
+/* An ordinary table or view name in the FROM clause */
+assert( pFrom->pTab==0 );
+pFrom->pTab = pTab =
+sqlite3LocateTable(pParse,0,pFrom->zName,pFrom->zDatabase);
+if( pTab==0 ) return WRC_Abort;
+pTab->nRef++;
+#if !defined(SQLITE_OMIT_VIEW) || !defined (SQLITE_OMIT_VIRTUALTABLE)
+if( pTab->pSelect || IsVirtual(pTab) ){
+/* We reach here if the named table is a really a view */
+if( sqlite3ViewGetColumnNames(pParse, pTab) ) return WRC_Abort;
+/* If pFrom->pSelect!=0 it means we are dealing with a
+** view within a view.  The SELECT structure has already been
+** copied by the outer view so we can skip the copy step here
+** in the inner view.
+*/
+if( pFrom->pSelect==0 ){
+pFrom->pSelect = sqlite3SelectDup(db, pTab->pSelect);
+sqlite3WalkSelect(pWalker, pFrom->pSelect);
+}
+}
+#endif
+}
+}
+/* Process NATURAL keywords, and ON and USING clauses of joins.
+*/
+if( db->mallocFailed || sqliteProcessJoin(pParse, p) ){
+return WRC_Abort;
+}
+/* For every "*" that occurs in the column list, insert the names of
+** all columns in all tables.  And for every TABLE.* insert the names
+** of all columns in TABLE.  The parser inserted a special expression
+** with the TK_ALL operator for each "*" that it found in the column list.
+** The following code just has to locate the TK_ALL expressions and expand
+** each one to the list of all columns in all tables.
+**
+** The first loop just checks to see if there are any "*" operators
+** that need expanding.
+*/
+for(k=0; k<pEList->nExpr; k++){
+Expr *pE = pEList->a[k].pExpr;
+if( pE->op==TK_ALL ) break;
+if( pE->op==TK_DOT && pE->pRight && pE->pRight->op==TK_ALL
+&& pE->pLeft && pE->pLeft->op==TK_ID ) break;
+}
+if( k<pEList->nExpr ){
+/*
+** If we get here it means the result set contains one or more "*"
+** operators that need to be expanded.  Loop through each expression
+** in the result set and expand them one by one.
+*/
+struct ExprList_item *a = pEList->a;
+ExprList *pNew = 0;
+int flags = pParse->db->flags;
+int longNames = (flags & SQLITE_FullColNames)!=0
+&& (flags & SQLITE_ShortColNames)==0;
+for(k=0; k<pEList->nExpr; k++){
+Expr *pE = a[k].pExpr;
+if( pE->op!=TK_ALL &&
+(pE->op!=TK_DOT || pE->pRight==0 || pE->pRight->op!=TK_ALL) ){
+/* This particular expression does not need to be expanded.
+*/
+pNew = sqlite3ExprListAppend(pParse, pNew, a[k].pExpr, 0);
+if( pNew ){
+pNew->a[pNew->nExpr-1].zName = a[k].zName;
+}
+a[k].pExpr = 0;
+a[k].zName = 0;
+}else{
+/* This expression is a "*" or a "TABLE.*" and needs to be
+** expanded. */
+int tableSeen = 0;      /* Set to 1 when TABLE matches */
+char *zTName;            /* text of name of TABLE */
+if( pE->op==TK_DOT && pE->pLeft ){
+zTName = sqlite3NameFromToken(db, &pE->pLeft->token);
+}else{
+zTName = 0;
+}
+for(i=0, pFrom=pTabList->a; i<pTabList->nSrc; i++, pFrom++){
+Table *pTab = pFrom->pTab;
+char *zTabName = pFrom->zAlias;
+if( zTabName==0 || zTabName[0]==0 ){
+zTabName = pTab->zName;
+}
+if( db->mallocFailed ) break;
+if( zTName && sqlite3StrICmp(zTName, zTabName)!=0 ){
+continue;
+}
+tableSeen = 1;
+for(j=0; j<pTab->nCol; j++){
+Expr *pExpr, *pRight;
+char *zName = pTab->aCol[j].zName;
+/* If a column is marked as 'hidden' (currently only possible
+** for virtual tables), do not include it in the expanded
+** result-set list.
+*/
+if( IsHiddenColumn(&pTab->aCol[j]) ){
+assert(IsVirtual(pTab));
+continue;
+}
+if( i>0 ){
+struct SrcList_item *pLeft = &pTabList->a[i-1];
+if( (pLeft[1].jointype & JT_NATURAL)!=0 &&
+columnIndex(pLeft->pTab, zName)>=0 ){
+/* In a NATURAL join, omit the join columns from the
+** table on the right */
+continue;
+}
+if( sqlite3IdListIndex(pLeft[1].pUsing, zName)>=0 ){
+/* In a join with a USING clause, omit columns in the
+** using clause from the table on the right. */
+continue;
+}
+}
+pRight = sqlite3PExpr(pParse, TK_ID, 0, 0, 0);
+if( pRight==0 ) break;
+setQuotedToken(pParse, &pRight->token, zName);
+if( longNames || pTabList->nSrc>1 ){
+Expr *pLeft = sqlite3PExpr(pParse, TK_ID, 0, 0, 0);
+pExpr = sqlite3PExpr(pParse, TK_DOT, pLeft, pRight, 0);
+if( pExpr==0 ) break;
+setQuotedToken(pParse, &pLeft->token, zTabName);
+setToken(&pExpr->span,
+sqlite3MPrintf(db, "%s.%s", zTabName, zName));
+pExpr->span.dyn = 1;
+pExpr->token.z = 0;
+pExpr->token.n = 0;
+pExpr->token.dyn = 0;
+}else{
+pExpr = pRight;
+pExpr->span = pExpr->token;
+pExpr->span.dyn = 0;
+}
+if( longNames ){
+pNew = sqlite3ExprListAppend(pParse, pNew, pExpr, &pExpr->span);
+}else{
+pNew = sqlite3ExprListAppend(pParse, pNew, pExpr, &pRight->token);
+}
+}
+}
+if( !tableSeen ){
+if( zTName ){
+sqlite3ErrorMsg(pParse, "no such table: %s", zTName);
+}else{
+sqlite3ErrorMsg(pParse, "no tables specified");
+}
+}
+sqlite3DbFree(db, zTName);
+}
+}
+sqlite3ExprListDelete(db, pEList);
+p->pEList = pNew;
+}
+#if SQLITE_MAX_COLUMN
+if( p->pEList && p->pEList->nExpr>db->aLimit[SQLITE_LIMIT_COLUMN] ){
+sqlite3ErrorMsg(pParse, "too many columns in result set");
+}
+#endif
+return WRC_Continue;
+}
+/*
+** No-op routine for the parse-tree walker.
+**
+** When this routine is the Walker.xExprCallback then expression trees
+** are walked without any actions being taken at each node.  Presumably,
+** when this routine is used for Walker.xExprCallback then
+** Walker.xSelectCallback is set to do something useful for every
+** subquery in the parser tree.
+*/
+static int exprWalkNoop(Walker *pWalker, Expr *pExpr){
+return WRC_Continue;
+}
+/*
+** This routine "expands" a SELECT statement and all of its subqueries.
+** For additional information on what it means to "expand" a SELECT
+** statement, see the comment on the selectExpand worker callback above.
+**
+** Expanding a SELECT statement is the first step in processing a
+** SELECT statement.  The SELECT statement must be expanded before
+** name resolution is performed.
+**
+** If anything goes wrong, an error message is written into pParse.
+** The calling function can detect the problem by looking at pParse->nErr
+** and/or pParse->db->mallocFailed.
+*/
+static void sqlite3SelectExpand(Parse *pParse, Select *pSelect){
+Walker w;
+w.xSelectCallback = selectExpander;
+w.xExprCallback = exprWalkNoop;
+w.pParse = pParse;
+sqlite3WalkSelect(&w, pSelect);
+}
+#ifndef SQLITE_OMIT_SUBQUERY
+/*
+** This is a Walker.xSelectCallback callback for the sqlite3SelectTypeInfo()
+** interface.
+**
+** For each FROM-clause subquery, add Column.zType and Column.zColl
+** information to the Table structure that represents the result set
+** of that subquery.
+**
+** The Table structure that represents the result set was constructed
+** by selectExpander() but the type and collation information was omitted
+** at that point because identifiers had not yet been resolved.  This
+** routine is called after identifier resolution.
+*/
+static int selectAddSubqueryTypeInfo(Walker *pWalker, Select *p){
+Parse *pParse;
+int i;
+SrcList *pTabList;
+struct SrcList_item *pFrom;
+assert( p->selFlags & SF_Resolved );
+if( (p->selFlags & SF_HasTypeInfo)==0 ){
+p->selFlags |= SF_HasTypeInfo;
+pParse = pWalker->pParse;
+pTabList = p->pSrc;
+for(i=0, pFrom=pTabList->a; i<pTabList->nSrc; i++, pFrom++){
+Table *pTab = pFrom->pTab;
+if( pTab && (pTab->tabFlags & TF_Ephemeral)!=0 ){
+/* A sub-query in the FROM clause of a SELECT */
+Select *pSel = pFrom->pSelect;
+assert( pSel );
+while( pSel->pPrior ) pSel = pSel->pPrior;
+selectAddColumnTypeAndCollation(pParse, pTab->nCol, pTab->aCol, pSel);
+}
+}
+}
+return WRC_Continue;
+}
+#endif
+/*
+** This routine adds datatype and collating sequence information to
+** the Table structures of all FROM-clause subqueries in a
+** SELECT statement.
+**
+** Use this routine after name resolution.
+*/
+static void sqlite3SelectAddTypeInfo(Parse *pParse, Select *pSelect){
+#ifndef SQLITE_OMIT_SUBQUERY
+Walker w;
+w.xSelectCallback = selectAddSubqueryTypeInfo;
+w.xExprCallback = exprWalkNoop;
+w.pParse = pParse;
+sqlite3WalkSelect(&w, pSelect);
+#endif
+}
+/*
+** This routine sets of a SELECT statement for processing.  The
+** following is accomplished:
+**
+**     *  VDBE Cursor numbers are assigned to all FROM-clause terms.
+**     *  Ephemeral Table objects are created for all FROM-clause subqueries.
+**     *  ON and USING clauses are shifted into WHERE statements
+**     *  Wildcards "*" and "TABLE.*" in result sets are expanded.
+**     *  Identifiers in expression are matched to tables.
+**
+** This routine acts recursively on all subqueries within the SELECT.
+*/
+void sqlite3SelectPrep(
+Parse *pParse,         /* The parser context */
+Select *p,             /* The SELECT statement being coded. */
+NameContext *pOuterNC  /* Name context for container */
+){
+sqlite3 *db;
+if( p==0 ) return;
+db = pParse->db;
+if( p->selFlags & SF_HasTypeInfo ) return;
+if( pParse->nErr || db->mallocFailed ) return;
+sqlite3SelectExpand(pParse, p);
+if( pParse->nErr || db->mallocFailed ) return;
+sqlite3ResolveSelectNames(pParse, p, pOuterNC);
+if( pParse->nErr || db->mallocFailed ) return;
+sqlite3SelectAddTypeInfo(pParse, p);
+}
+/*
+** Reset the aggregate accumulator.
+**
+** The aggregate accumulator is a set of memory cells that hold
+** intermediate results while calculating an aggregate.  This
+** routine simply stores NULLs in all of those memory cells.
+*/
+static void resetAccumulator(Parse *pParse, AggInfo *pAggInfo){
+Vdbe *v = pParse->pVdbe;
+int i;
+struct AggInfo_func *pFunc;
+if( pAggInfo->nFunc+pAggInfo->nColumn==0 ){
+return;
+}
+for(i=0; i<pAggInfo->nColumn; i++){
+sqlite3VdbeAddOp2(v, OP_Null, 0, pAggInfo->aCol[i].iMem);
+}
+for(pFunc=pAggInfo->aFunc, i=0; i<pAggInfo->nFunc; i++, pFunc++){
+sqlite3VdbeAddOp2(v, OP_Null, 0, pFunc->iMem);
+if( pFunc->iDistinct>=0 ){
+Expr *pE = pFunc->pExpr;
+if( pE->pList==0 || pE->pList->nExpr!=1 ){
+sqlite3ErrorMsg(pParse, "DISTINCT in aggregate must be followed "
+"by an expression");
+pFunc->iDistinct = -1;
+}else{
+KeyInfo *pKeyInfo = keyInfoFromExprList(pParse, pE->pList);
+sqlite3VdbeAddOp4(v, OP_OpenEphemeral, pFunc->iDistinct, 0, 0,
+(char*)pKeyInfo, P4_KEYINFO_HANDOFF);
+}
+}
+}
+}
+/*
+** Invoke the OP_AggFinalize opcode for every aggregate function
+** in the AggInfo structure.
+*/
+static void finalizeAggFunctions(Parse *pParse, AggInfo *pAggInfo){
+Vdbe *v = pParse->pVdbe;
+int i;
+struct AggInfo_func *pF;
+for(i=0, pF=pAggInfo->aFunc; i<pAggInfo->nFunc; i++, pF++){
+ExprList *pList = pF->pExpr->pList;
+sqlite3VdbeAddOp4(v, OP_AggFinal, pF->iMem, pList ? pList->nExpr : 0, 0,
+(void*)pF->pFunc, P4_FUNCDEF);
+}
+}
+/*
+** Update the accumulator memory cells for an aggregate based on
+** the current cursor position.
+*/
+static void updateAccumulator(Parse *pParse, AggInfo *pAggInfo){
+Vdbe *v = pParse->pVdbe;
+int i;
+struct AggInfo_func *pF;
+struct AggInfo_col *pC;
+pAggInfo->directMode = 1;
+for(i=0, pF=pAggInfo->aFunc; i<pAggInfo->nFunc; i++, pF++){
+int nArg;
+int addrNext = 0;
+int regAgg;
+ExprList *pList = pF->pExpr->pList;
+if( pList ){
+nArg = pList->nExpr;
+regAgg = sqlite3GetTempRange(pParse, nArg);
+sqlite3ExprCodeExprList(pParse, pList, regAgg, 0);
+}else{
+nArg = 0;
+regAgg = 0;
+}
+if( pF->iDistinct>=0 ){
+addrNext = sqlite3VdbeMakeLabel(v);
+assert( nArg==1 );
+codeDistinct(pParse, pF->iDistinct, addrNext, 1, regAgg);
+}
+if( pF->pFunc->needCollSeq ){
+CollSeq *pColl = 0;
+struct ExprList_item *pItem;
+int j;
+assert( pList!=0 );  /* pList!=0 if pF->pFunc->needCollSeq is true */
+for(j=0, pItem=pList->a; !pColl && j<nArg; j++, pItem++){
+pColl = sqlite3ExprCollSeq(pParse, pItem->pExpr);
+}
+if( !pColl ){
+pColl = pParse->db->pDfltColl;
+}
+sqlite3VdbeAddOp4(v, OP_CollSeq, 0, 0, 0, (char *)pColl, P4_COLLSEQ);
+}
+sqlite3VdbeAddOp4(v, OP_AggStep, 0, regAgg, pF->iMem,
+(void*)pF->pFunc, P4_FUNCDEF);
+sqlite3VdbeChangeP5(v, nArg);
+sqlite3ReleaseTempRange(pParse, regAgg, nArg);
+sqlite3ExprCacheAffinityChange(pParse, regAgg, nArg);
+if( addrNext ){
+sqlite3VdbeResolveLabel(v, addrNext);
+}
+}
+for(i=0, pC=pAggInfo->aCol; i<pAggInfo->nAccumulator; i++, pC++){
+sqlite3ExprCode(pParse, pC->pExpr, pC->iMem);
+}
+pAggInfo->directMode = 0;
+}
+/*
+** Generate code for the SELECT statement given in the p argument.
+**
+** The results are distributed in various ways depending on the
+** contents of the SelectDest structure pointed to by argument pDest
+** as follows:
+**
+**     pDest->eDest    Result
+**     ------------    -------------------------------------------
+**     SRT_Output      Generate a row of output (using the OP_ResultRow
+**                     opcode) for each row in the result set.
+**
+**     SRT_Mem         Only valid if the result is a single column.
+**                     Store the first column of the first result row
+**                     in register pDest->iParm then abandon the rest
+**                     of the query.  This destination implies "LIMIT 1".
+**
+**     SRT_Set         The result must be a single column.  Store each
+**                     row of result as the key in table pDest->iParm.
+**                     Apply the affinity pDest->affinity before storing
+**                     results.  Used to implement "IN (SELECT ...)".
+**
+**     SRT_Union       Store results as a key in a temporary table pDest->iParm.
+**
+**     SRT_Except      Remove results from the temporary table pDest->iParm.
+**
+**     SRT_Table       Store results in temporary table pDest->iParm.
+**                     This is like SRT_EphemTab except that the table
+**                     is assumed to already be open.
+**
+**     SRT_EphemTab    Create an temporary table pDest->iParm and store
+**                     the result there. The cursor is left open after
+**                     returning.  This is like SRT_Table except that
+**                     this destination uses OP_OpenEphemeral to create
+**                     the table first.
+**
+**     SRT_Coroutine   Generate a co-routine that returns a new row of
+**                     results each time it is invoked.  The entry point
+**                     of the co-routine is stored in register pDest->iParm.
+**
+**     SRT_Exists      Store a 1 in memory cell pDest->iParm if the result
+**                     set is not empty.
+**
+**     SRT_Discard     Throw the results away.  This is used by SELECT
+**                     statements within triggers whose only purpose is
+**                     the side-effects of functions.
+**
+** This routine returns the number of errors.  If any errors are
+** encountered, then an appropriate error message is left in
+** pParse->zErrMsg.
+**
+** This routine does NOT free the Select structure passed in.  The
+** calling function needs to do that.
+*/
+int sqlite3Select(
+Parse *pParse,         /* The parser context */
+Select *p,             /* The SELECT statement being coded. */
+SelectDest *pDest      /* What to do with the query results */
+){
+int i, j;              /* Loop counters */
+WhereInfo *pWInfo;     /* Return from sqlite3WhereBegin() */
+Vdbe *v;               /* The virtual machine under construction */
+int isAgg;             /* True for select lists like "count(*)" */
+ExprList *pEList;      /* List of columns to extract. */
+SrcList *pTabList;     /* List of tables to select from */
+Expr *pWhere;          /* The WHERE clause.  May be NULL */
+ExprList *pOrderBy;    /* The ORDER BY clause.  May be NULL */
+ExprList *pGroupBy;    /* The GROUP BY clause.  May be NULL */
+Expr *pHaving;         /* The HAVING clause.  May be NULL */
+int isDistinct;        /* True if the DISTINCT keyword is present */
+int distinct;          /* Table to use for the distinct set */
+int rc = 1;            /* Value to return from this function */
+int addrSortIndex;     /* Address of an OP_OpenEphemeral instruction */
+AggInfo sAggInfo;      /* Information used by aggregate queries */
+int iEnd;              /* Address of the end of the query */
+sqlite3 *db;           /* The database connection */
+db = pParse->db;
+if( p==0 || db->mallocFailed || pParse->nErr ){
+return 1;
+}
+if( sqlite3AuthCheck(pParse, SQLITE_SELECT, 0, 0, 0) ) return 1;
+memset(&sAggInfo, 0, sizeof(sAggInfo));
+pOrderBy = p->pOrderBy;
+if( IgnorableOrderby(pDest) ){
+p->pOrderBy = 0;
+/* In these cases the DISTINCT operator makes no difference to the
+** results, so remove it if it were specified.
+*/
+assert(pDest->eDest==SRT_Exists || pDest->eDest==SRT_Union ||
+pDest->eDest==SRT_Except || pDest->eDest==SRT_Discard);
+p->selFlags &= ~SF_Distinct;
+}
+sqlite3SelectPrep(pParse, p, 0);
+if( pParse->nErr ){
+goto select_end;
+}
+p->pOrderBy = pOrderBy;
+/* Make local copies of the parameters for this query.
+*/
+pTabList = p->pSrc;
+isAgg = (p->selFlags & SF_Aggregate)!=0;
+pEList = p->pEList;
+if( pEList==0 ) goto select_end;
+/*
+** Do not even attempt to generate any code if we have already seen
+** errors before this routine starts.
+*/
+if( pParse->nErr>0 ) goto select_end;
+/* ORDER BY is ignored for some destinations.
+*/
+if( IgnorableOrderby(pDest) ){
+pOrderBy = 0;
+}
+/* Begin generating code.
+*/
+v = sqlite3GetVdbe(pParse);
+if( v==0 ) goto select_end;
+/* Generate code for all sub-queries in the FROM clause
+*/
+#if !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW)
+for(i=0; !p->pPrior && i<pTabList->nSrc; i++){
+struct SrcList_item *pItem = &pTabList->a[i];
+SelectDest dest;
+Select *pSub = pItem->pSelect;
+int isAggSub;
+if( pSub==0 || pItem->isPopulated ) continue;
+/* Increment Parse.nHeight by the height of the largest expression
+** tree refered to by this, the parent select. The child select
+** may contain expression trees of at most
+** (SQLITE_MAX_EXPR_DEPTH-Parse.nHeight) height. This is a bit
+** more conservative than necessary, but much easier than enforcing
+** an exact limit.
+*/
+pParse->nHeight += sqlite3SelectExprHeight(p);
+/* Check to see if the subquery can be absorbed into the parent. */
+isAggSub = (pSub->selFlags & SF_Aggregate)!=0;
+if( flattenSubquery(pParse, p, i, isAgg, isAggSub) ){
+if( isAggSub ){
+isAgg = 1;
+p->selFlags |= SF_Aggregate;
+}
+i = -1;
+}else{
+sqlite3SelectDestInit(&dest, SRT_EphemTab, pItem->iCursor);
+assert( pItem->isPopulated==0 );
+sqlite3Select(pParse, pSub, &dest);
+pItem->isPopulated = 1;
+}
+if( pParse->nErr || db->mallocFailed ){
+goto select_end;
+}
+pParse->nHeight -= sqlite3SelectExprHeight(p);
+pTabList = p->pSrc;
+if( !IgnorableOrderby(pDest) ){
+pOrderBy = p->pOrderBy;
+}
+}
+pEList = p->pEList;
+#endif
+pWhere = p->pWhere;
+pGroupBy = p->pGroupBy;
+pHaving = p->pHaving;
+isDistinct = (p->selFlags & SF_Distinct)!=0;
+#ifndef SQLITE_OMIT_COMPOUND_SELECT
+/* If there is are a sequence of queries, do the earlier ones first.
+*/
+if( p->pPrior ){
+if( p->pRightmost==0 ){
+Select *pLoop, *pRight = 0;
+int cnt = 0;
+int mxSelect;
+for(pLoop=p; pLoop; pLoop=pLoop->pPrior, cnt++){
+pLoop->pRightmost = p;
+pLoop->pNext = pRight;
+pRight = pLoop;
+}
+mxSelect = db->aLimit[SQLITE_LIMIT_COMPOUND_SELECT];
+if( mxSelect && cnt>mxSelect ){
+sqlite3ErrorMsg(pParse, "too many terms in compound SELECT");
+return 1;
+}
+}
+return multiSelect(pParse, p, pDest);
+}
+#endif
+/* If writing to memory or generating a set
+** only a single column may be output.
+*/
+#ifndef SQLITE_OMIT_SUBQUERY
+if( checkForMultiColumnSelectError(pParse, pDest, pEList->nExpr) ){
+goto select_end;
+}
+#endif
+/* If possible, rewrite the query to use GROUP BY instead of DISTINCT.
+** GROUP BY might use an index, DISTINCT never does.
+*/
+if( (p->selFlags & (SF_Distinct|SF_Aggregate))==SF_Distinct && !p->pGroupBy ){
+p->pGroupBy = sqlite3ExprListDup(db, p->pEList);
+pGroupBy = p->pGroupBy;
+p->selFlags &= ~SF_Distinct;
+isDistinct = 0;
+}
+/* If there is an ORDER BY clause, then this sorting
+** index might end up being unused if the data can be
+** extracted in pre-sorted order.  If that is the case, then the
+** OP_OpenEphemeral instruction will be changed to an OP_Noop once
+** we figure out that the sorting index is not needed.  The addrSortIndex
+** variable is used to facilitate that change.
+*/
+if( pOrderBy ){
+KeyInfo *pKeyInfo;
+pKeyInfo = keyInfoFromExprList(pParse, pOrderBy);
+pOrderBy->iECursor = pParse->nTab++;
+p->addrOpenEphm[2] = addrSortIndex =
+sqlite3VdbeAddOp4(v, OP_OpenEphemeral,
+pOrderBy->iECursor, pOrderBy->nExpr+2, 0,
+(char*)pKeyInfo, P4_KEYINFO_HANDOFF);
+}else{
+addrSortIndex = -1;
+}
+/* If the output is destined for a temporary table, open that table.
+*/
+if( pDest->eDest==SRT_EphemTab ){
+sqlite3VdbeAddOp2(v, OP_OpenEphemeral, pDest->iParm, pEList->nExpr);
+}
+/* Set the limiter.
+*/
+iEnd = sqlite3VdbeMakeLabel(v);
+computeLimitRegisters(pParse, p, iEnd);
+/* Open a virtual index to use for the distinct set.
+*/
+if( isDistinct ){
+KeyInfo *pKeyInfo;
+assert( isAgg || pGroupBy );
+distinct = pParse->nTab++;
+pKeyInfo = keyInfoFromExprList(pParse, p->pEList);
+sqlite3VdbeAddOp4(v, OP_OpenEphemeral, distinct, 0, 0,
+(char*)pKeyInfo, P4_KEYINFO_HANDOFF);
+}else{
+distinct = -1;
+}
+/* Aggregate and non-aggregate queries are handled differently */
+if( !isAgg && pGroupBy==0 ){
+/* This case is for non-aggregate queries
+** Begin the database scan
+*/
+pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, &pOrderBy, 0);
+if( pWInfo==0 ) goto select_end;
+/* If sorting index that was created by a prior OP_OpenEphemeral
+** instruction ended up not being needed, then change the OP_OpenEphemeral
+** into an OP_Noop.
+*/
+if( addrSortIndex>=0 && pOrderBy==0 ){
+sqlite3VdbeChangeToNoop(v, addrSortIndex, 1);
+p->addrOpenEphm[2] = -1;
+}
+/* Use the standard inner loop
+*/
+assert(!isDistinct);
+selectInnerLoop(pParse, p, pEList, 0, 0, pOrderBy, -1, pDest,
+pWInfo->iContinue, pWInfo->iBreak);
+/* End the database scan loop.
+*/
+sqlite3WhereEnd(pWInfo);
+}else{
+/* This is the processing for aggregate queries */
+NameContext sNC;    /* Name context for processing aggregate information */
+int iAMem;          /* First Mem address for storing current GROUP BY */
+int iBMem;          /* First Mem address for previous GROUP BY */
+int iUseFlag;       /* Mem address holding flag indicating that at least
+** one row of the input to the aggregator has been
+** processed */
+int iAbortFlag;     /* Mem address which causes query abort if positive */
+int groupBySort;    /* Rows come from source in GROUP BY order */
+int addrEnd;        /* End of processing for this SELECT */
+/* Remove any and all aliases between the result set and the
+** GROUP BY clause.
+*/
+if( pGroupBy ){
+int i;                        /* Loop counter */
+struct ExprList_item *pItem;  /* For looping over expression in a list */
+for(i=p->pEList->nExpr, pItem=p->pEList->a; i>0; i--, pItem++){
+pItem->iAlias = 0;
+}
+for(i=pGroupBy->nExpr, pItem=pGroupBy->a; i>0; i--, pItem++){
+pItem->iAlias = 0;
+}
+}
+/* Create a label to jump to when we want to abort the query */
+addrEnd = sqlite3VdbeMakeLabel(v);
+/* Convert TK_COLUMN nodes into TK_AGG_COLUMN and make entries in
+** sAggInfo for all TK_AGG_FUNCTION nodes in expressions of the
+** SELECT statement.
+*/
+memset(&sNC, 0, sizeof(sNC));
+sNC.pParse = pParse;
+sNC.pSrcList = pTabList;
+sNC.pAggInfo = &sAggInfo;
+sAggInfo.nSortingColumn = pGroupBy ? pGroupBy->nExpr+1 : 0;
+sAggInfo.pGroupBy = pGroupBy;
+sqlite3ExprAnalyzeAggList(&sNC, pEList);
+sqlite3ExprAnalyzeAggList(&sNC, pOrderBy);
+if( pHaving ){
+sqlite3ExprAnalyzeAggregates(&sNC, pHaving);
+}
+sAggInfo.nAccumulator = sAggInfo.nColumn;
+for(i=0; i<sAggInfo.nFunc; i++){
+sqlite3ExprAnalyzeAggList(&sNC, sAggInfo.aFunc[i].pExpr->pList);
+}
+if( db->mallocFailed ) goto select_end;
+/* Processing for aggregates with GROUP BY is very different and
+** much more complex than aggregates without a GROUP BY.
+*/
+if( pGroupBy ){
+KeyInfo *pKeyInfo;  /* Keying information for the group by clause */
+int j1;             /* A-vs-B comparision jump */
+int addrOutputRow;  /* Start of subroutine that outputs a result row */
+int regOutputRow;   /* Return address register for output subroutine */
+int addrSetAbort;   /* Set the abort flag and return */
+int addrTopOfLoop;  /* Top of the input loop */
+int addrSortingIdx; /* The OP_OpenEphemeral for the sorting index */
+int addrReset;      /* Subroutine for resetting the accumulator */
+int regReset;       /* Return address register for reset subroutine */
+/* If there is a GROUP BY clause we might need a sorting index to
+** implement it.  Allocate that sorting index now.  If it turns out
+** that we do not need it after all, the OpenEphemeral instruction
+** will be converted into a Noop.
+*/
+sAggInfo.sortingIdx = pParse->nTab++;
+pKeyInfo = keyInfoFromExprList(pParse, pGroupBy);
+addrSortingIdx = sqlite3VdbeAddOp4(v, OP_OpenEphemeral,
+sAggInfo.sortingIdx, sAggInfo.nSortingColumn,
+0, (char*)pKeyInfo, P4_KEYINFO_HANDOFF);
+/* Initialize memory locations used by GROUP BY aggregate processing
+*/
+iUseFlag = ++pParse->nMem;
+iAbortFlag = ++pParse->nMem;
+regOutputRow = ++pParse->nMem;
+addrOutputRow = sqlite3VdbeMakeLabel(v);
+regReset = ++pParse->nMem;
+addrReset = sqlite3VdbeMakeLabel(v);
+iAMem = pParse->nMem + 1;
+pParse->nMem += pGroupBy->nExpr;
+iBMem = pParse->nMem + 1;
+pParse->nMem += pGroupBy->nExpr;
+sqlite3VdbeAddOp2(v, OP_Integer, 0, iAbortFlag);
+VdbeComment((v, "clear abort flag"));
+sqlite3VdbeAddOp2(v, OP_Integer, 0, iUseFlag);
+VdbeComment((v, "indicate accumulator empty"));
+/* Begin a loop that will extract all source rows in GROUP BY order.
+** This might involve two separate loops with an OP_Sort in between, or
+** it might be a single loop that uses an index to extract information
+** in the right order to begin with.
+*/
+sqlite3VdbeAddOp2(v, OP_Gosub, regReset, addrReset);
+pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, &pGroupBy, 0);
+if( pWInfo==0 ) goto select_end;
+if( pGroupBy==0 ){
+/* The optimizer is able to deliver rows in group by order so
+** we do not have to sort.  The OP_OpenEphemeral table will be
+** cancelled later because we still need to use the pKeyInfo
+*/
+pGroupBy = p->pGroupBy;
+groupBySort = 0;
+}else{
+/* Rows are coming out in undetermined order.  We have to push
+** each row into a sorting index, terminate the first loop,
+** then loop over the sorting index in order to get the output
+** in sorted order
+*/
+int regBase;
+int regRecord;
+int nCol;
+int nGroupBy;
+groupBySort = 1;
+nGroupBy = pGroupBy->nExpr;
+nCol = nGroupBy + 1;
+j = nGroupBy+1;
+for(i=0; i<sAggInfo.nColumn; i++){
+if( sAggInfo.aCol[i].iSorterColumn>=j ){
+nCol++;
+j++;
+}
+}
+regBase = sqlite3GetTempRange(pParse, nCol);
+sqlite3ExprCodeExprList(pParse, pGroupBy, regBase, 0);
+sqlite3VdbeAddOp2(v, OP_Sequence, sAggInfo.sortingIdx,regBase+nGroupBy);
+j = nGroupBy+1;
+for(i=0; i<sAggInfo.nColumn; i++){
+struct AggInfo_col *pCol = &sAggInfo.aCol[i];
+if( pCol->iSorterColumn>=j ){
+int r1 = j + regBase;
+int r2;
+r2 = sqlite3ExprCodeGetColumn(pParse,
+pCol->pTab, pCol->iColumn, pCol->iTable, r1, 0);
+if( r1!=r2 ){
+sqlite3VdbeAddOp2(v, OP_SCopy, r2, r1);
+}
+j++;
+}
+}
+regRecord = sqlite3GetTempReg(pParse);
+sqlite3VdbeAddOp3(v, OP_MakeRecord, regBase, nCol, regRecord);
+sqlite3VdbeAddOp2(v, OP_IdxInsert, sAggInfo.sortingIdx, regRecord);
+sqlite3ReleaseTempReg(pParse, regRecord);
+sqlite3ReleaseTempRange(pParse, regBase, nCol);
+sqlite3WhereEnd(pWInfo);
+sqlite3VdbeAddOp2(v, OP_Sort, sAggInfo.sortingIdx, addrEnd);
+VdbeComment((v, "GROUP BY sort"));
+sAggInfo.useSortingIdx = 1;
+}
+/* Evaluate the current GROUP BY terms and store in b0, b1, b2...
+** (b0 is memory location iBMem+0, b1 is iBMem+1, and so forth)
+** Then compare the current GROUP BY terms against the GROUP BY terms
+** from the previous row currently stored in a0, a1, a2...
+*/
+addrTopOfLoop = sqlite3VdbeCurrentAddr(v);
+for(j=0; j<pGroupBy->nExpr; j++){
+if( groupBySort ){
+sqlite3VdbeAddOp3(v, OP_Column, sAggInfo.sortingIdx, j, iBMem+j);
+}else{
+sAggInfo.directMode = 1;
+sqlite3ExprCode(pParse, pGroupBy->a[j].pExpr, iBMem+j);
+}
+}
+sqlite3VdbeAddOp4(v, OP_Compare, iAMem, iBMem, pGroupBy->nExpr,
+(char*)pKeyInfo, P4_KEYINFO);
+j1 = sqlite3VdbeCurrentAddr(v);
+sqlite3VdbeAddOp3(v, OP_Jump, j1+1, 0, j1+1);
+/* Generate code that runs whenever the GROUP BY changes.
+** Changes in the GROUP BY are detected by the previous code
+** block.  If there were no changes, this block is skipped.
+**
+** This code copies current group by terms in b0,b1,b2,...
+** over to a0,a1,a2.  It then calls the output subroutine
+** and resets the aggregate accumulator registers in preparation
+** for the next GROUP BY batch.
+*/
+sqlite3ExprCodeMove(pParse, iBMem, iAMem, pGroupBy->nExpr);
+sqlite3VdbeAddOp2(v, OP_Gosub, regOutputRow, addrOutputRow);
+VdbeComment((v, "output one row"));
+sqlite3VdbeAddOp2(v, OP_IfPos, iAbortFlag, addrEnd);
+VdbeComment((v, "check abort flag"));
+sqlite3VdbeAddOp2(v, OP_Gosub, regReset, addrReset);
+VdbeComment((v, "reset accumulator"));
+/* Update the aggregate accumulators based on the content of
+** the current row
+*/
+sqlite3VdbeJumpHere(v, j1);
+updateAccumulator(pParse, &sAggInfo);
+sqlite3VdbeAddOp2(v, OP_Integer, 1, iUseFlag);
+VdbeComment((v, "indicate data in accumulator"));
+/* End of the loop
+*/
+if( groupBySort ){
+sqlite3VdbeAddOp2(v, OP_Next, sAggInfo.sortingIdx, addrTopOfLoop);
+}else{
+sqlite3WhereEnd(pWInfo);
+sqlite3VdbeChangeToNoop(v, addrSortingIdx, 1);
+}
+/* Output the final row of result
+*/
+sqlite3VdbeAddOp2(v, OP_Gosub, regOutputRow, addrOutputRow);
+VdbeComment((v, "output final row"));
+/* Jump over the subroutines
+*/
+sqlite3VdbeAddOp2(v, OP_Goto, 0, addrEnd);
+/* Generate a subroutine that outputs a single row of the result
+** set.  This subroutine first looks at the iUseFlag.  If iUseFlag
+** is less than or equal to zero, the subroutine is a no-op.  If
+** the processing calls for the query to abort, this subroutine
+** increments the iAbortFlag memory location before returning in
+** order to signal the caller to abort.
+*/
+addrSetAbort = sqlite3VdbeCurrentAddr(v);
+sqlite3VdbeAddOp2(v, OP_Integer, 1, iAbortFlag);
+VdbeComment((v, "set abort flag"));
+sqlite3VdbeAddOp1(v, OP_Return, regOutputRow);
+sqlite3VdbeResolveLabel(v, addrOutputRow);
+addrOutputRow = sqlite3VdbeCurrentAddr(v);
+sqlite3VdbeAddOp2(v, OP_IfPos, iUseFlag, addrOutputRow+2);
+VdbeComment((v, "Groupby result generator entry point"));
+sqlite3VdbeAddOp1(v, OP_Return, regOutputRow);
+finalizeAggFunctions(pParse, &sAggInfo);
+if( pHaving ){
+sqlite3ExprIfFalse(pParse, pHaving, addrOutputRow+1, SQLITE_JUMPIFNULL);
+}
+selectInnerLoop(pParse, p, p->pEList, 0, 0, pOrderBy,
+distinct, pDest,
+addrOutputRow+1, addrSetAbort);
+sqlite3VdbeAddOp1(v, OP_Return, regOutputRow);
+VdbeComment((v, "end groupby result generator"));
+/* Generate a subroutine that will reset the group-by accumulator
+*/
+sqlite3VdbeResolveLabel(v, addrReset);
+resetAccumulator(pParse, &sAggInfo);
+sqlite3VdbeAddOp1(v, OP_Return, regReset);
+} /* endif pGroupBy */
+else {
+ExprList *pMinMax = 0;
+ExprList *pDel = 0;
+u8 flag;
+/* Check if the query is of one of the following forms:
+**
+**   SELECT min(x) FROM ...
+**   SELECT max(x) FROM ...
+**
+** If it is, then ask the code in where.c to attempt to sort results
+** as if there was an "ORDER ON x" or "ORDER ON x DESC" clause.
+** If where.c is able to produce results sorted in this order, then
+** add vdbe code to break out of the processing loop after the
+** first iteration (since the first iteration of the loop is
+** guaranteed to operate on the row with the minimum or maximum
+** value of x, the only row required).
+**
+** A special flag must be passed to sqlite3WhereBegin() to slightly
+** modify behaviour as follows:
+**
+**   + If the query is a "SELECT min(x)", then the loop coded by
+**     where.c should not iterate over any values with a NULL value
+**     for x.
+**
+**   + The optimizer code in where.c (the thing that decides which
+**     index or indices to use) should place a different priority on
+**     satisfying the 'ORDER BY' clause than it does in other cases.
+**     Refer to code and comments in where.c for details.
+*/
+flag = minMaxQuery(pParse, p);
+if( flag ){
+pDel = pMinMax = sqlite3ExprListDup(db, p->pEList->a[0].pExpr->pList);
+if( pMinMax && !db->mallocFailed ){
+pMinMax->a[0].sortOrder = flag!=WHERE_ORDERBY_MIN;
+pMinMax->a[0].pExpr->op = TK_COLUMN;
+}
+}
+/* This case runs if the aggregate has no GROUP BY clause.  The
+** processing is much simpler since there is only a single row
+** of output.
+*/
+resetAccumulator(pParse, &sAggInfo);
+pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, &pMinMax, flag);
+if( pWInfo==0 ){
+sqlite3ExprListDelete(db, pDel);
+goto select_end;
+}
+updateAccumulator(pParse, &sAggInfo);
+if( !pMinMax && flag ){
+sqlite3VdbeAddOp2(v, OP_Goto, 0, pWInfo->iBreak);
+VdbeComment((v, "%s() by index",(flag==WHERE_ORDERBY_MIN?"min":"max")));
+}
+sqlite3WhereEnd(pWInfo);
+finalizeAggFunctions(pParse, &sAggInfo);
+pOrderBy = 0;
+if( pHaving ){
+sqlite3ExprIfFalse(pParse, pHaving, addrEnd, SQLITE_JUMPIFNULL);
+}
+selectInnerLoop(pParse, p, p->pEList, 0, 0, 0, -1,
+pDest, addrEnd, addrEnd);
+sqlite3ExprListDelete(db, pDel);
+}
+sqlite3VdbeResolveLabel(v, addrEnd);
+} /* endif aggregate query */
+/* If there is an ORDER BY clause, then we need to sort the results
+** and send them to the callback one by one.
+*/
+if( pOrderBy ){
+generateSortTail(pParse, p, v, pEList->nExpr, pDest);
+}
+/* Jump here to skip this query
+*/
+sqlite3VdbeResolveLabel(v, iEnd);
+/* The SELECT was successfully coded.   Set the return code to 0
+** to indicate no errors.
+*/
+rc = 0;
+/* Control jumps to here if an error is encountered above, or upon
+** successful coding of the SELECT.
+*/
+select_end:
+/* Identify column names if results of the SELECT are to be output.
+*/
+if( rc==SQLITE_OK && pDest->eDest==SRT_Output ){
+generateColumnNames(pParse, pTabList, pEList);
+}
+sqlite3DbFree(db, sAggInfo.aCol);
+sqlite3DbFree(db, sAggInfo.aFunc);
+return rc;
+}
+#if defined(SQLITE_DEBUG)
+/*
+*******************************************************************************
+** The following code is used for testing and debugging only.  The code
+** that follows does not appear in normal builds.
+**
+** These routines are used to print out the content of all or part of a
+** parse structures such as Select or Expr.  Such printouts are useful
+** for helping to understand what is happening inside the code generator
+** during the execution of complex SELECT statements.
+**
+** These routine are not called anywhere from within the normal
+** code base.  Then are intended to be called from within the debugger
+** or from temporary "printf" statements inserted for debugging.
+*/
+void sqlite3PrintExpr(Expr *p){
+if( p->token.z && p->token.n>0 ){
+sqlite3DebugPrintf("(%.*s", p->token.n, p->token.z);
+}else{
+sqlite3DebugPrintf("(%d", p->op);
+}
+if( p->pLeft ){
+sqlite3DebugPrintf(" ");
+sqlite3PrintExpr(p->pLeft);
+}
+if( p->pRight ){
+sqlite3DebugPrintf(" ");
+sqlite3PrintExpr(p->pRight);
+}
+sqlite3DebugPrintf(")");
+}
+void sqlite3PrintExprList(ExprList *pList){
+int i;
+for(i=0; i<pList->nExpr; i++){
+sqlite3PrintExpr(pList->a[i].pExpr);
+if( i<pList->nExpr-1 ){
+sqlite3DebugPrintf(", ");
+}
+}
+}
+void sqlite3PrintSelect(Select *p, int indent){
+sqlite3DebugPrintf("%*sSELECT(%p) ", indent, "", p);
+sqlite3PrintExprList(p->pEList);
+sqlite3DebugPrintf("\n");
+if( p->pSrc ){
+char *zPrefix;
+int i;
+zPrefix = "FROM";
+for(i=0; i<p->pSrc->nSrc; i++){
+struct SrcList_item *pItem = &p->pSrc->a[i];
+sqlite3DebugPrintf("%*s ", indent+6, zPrefix);
+zPrefix = "";
+if( pItem->pSelect ){
+sqlite3DebugPrintf("(\n");
+sqlite3PrintSelect(pItem->pSelect, indent+10);
+sqlite3DebugPrintf("%*s)", indent+8, "");
+}else if( pItem->zName ){
+sqlite3DebugPrintf("%s", pItem->zName);
+}
+if( pItem->pTab ){
+sqlite3DebugPrintf("(table: %s)", pItem->pTab->zName);
+}
+if( pItem->zAlias ){
+sqlite3DebugPrintf(" AS %s", pItem->zAlias);
+}
+if( i<p->pSrc->nSrc-1 ){
+sqlite3DebugPrintf(",");
+}
+sqlite3DebugPrintf("\n");
+}
+}
+if( p->pWhere ){
+sqlite3DebugPrintf("%*s WHERE ", indent, "");
+sqlite3PrintExpr(p->pWhere);
+sqlite3DebugPrintf("\n");
+}
+if( p->pGroupBy ){
+sqlite3DebugPrintf("%*s GROUP BY ", indent, "");
+sqlite3PrintExprList(p->pGroupBy);
+sqlite3DebugPrintf("\n");
+}
+if( p->pHaving ){
+sqlite3DebugPrintf("%*s HAVING ", indent, "");
+sqlite3PrintExpr(p->pHaving);
+sqlite3DebugPrintf("\n");
+}
+if( p->pOrderBy ){
+sqlite3DebugPrintf("%*s ORDER BY ", indent, "");
+sqlite3PrintExprList(p->pOrderBy);
+sqlite3DebugPrintf("\n");
+}
+}
+/* End of the structure debug printing code
+*****************************************************************************/
+#endif /* defined(SQLITE_TEST) || defined(SQLITE_DEBUG) */