--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/persistentstorage/sql/SQLite/where.c Fri Jan 22 11:06:30 2010 +0200
@@ -0,0 +1,2895 @@
+/*
+** 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 module contains C code that generates VDBE code used to process
+** the WHERE clause of SQL statements. This module is responsible for
+** generating the code that loops through a table looking for applicable
+** rows. Indices are selected and used to speed the search when doing
+** so is applicable. Because this module is responsible for selecting
+** indices, you might also think of this module as the "query optimizer".
+**
+** $Id: where.c,v 1.319 2008/08/01 17:37:41 danielk1977 Exp $
+*/
+#include "sqliteInt.h"
+
+/*
+** The number of bits in a Bitmask. "BMS" means "BitMask Size".
+*/
+#define BMS (sizeof(Bitmask)*8)
+
+/*
+** Trace output macros
+*/
+#if defined(SQLITE_TEST) || defined(SQLITE_DEBUG)
+int sqlite3WhereTrace = 0;
+#endif
+#if 0
+# define WHERETRACE(X) if(sqlite3WhereTrace) sqlite3DebugPrintf X
+#else
+# define WHERETRACE(X)
+#endif
+
+/* Forward reference
+*/
+typedef struct WhereClause WhereClause;
+typedef struct ExprMaskSet ExprMaskSet;
+
+/*
+** The query generator uses an array of instances of this structure to
+** help it analyze the subexpressions of the WHERE clause. Each WHERE
+** clause subexpression is separated from the others by an AND operator.
+**
+** All WhereTerms are collected into a single WhereClause structure.
+** The following identity holds:
+**
+** WhereTerm.pWC->a[WhereTerm.idx] == WhereTerm
+**
+** When a term is of the form:
+**
+** X <op> <expr>
+**
+** where X is a column name and <op> is one of certain operators,
+** then WhereTerm.leftCursor and WhereTerm.leftColumn record the
+** cursor number and column number for X. WhereTerm.operator records
+** the <op> using a bitmask encoding defined by WO_xxx below. The
+** use of a bitmask encoding for the operator allows us to search
+** quickly for terms that match any of several different operators.
+**
+** prereqRight and prereqAll record sets of cursor numbers,
+** but they do so indirectly. A single ExprMaskSet structure translates
+** cursor number into bits and the translated bit is stored in the prereq
+** fields. The translation is used in order to maximize the number of
+** bits that will fit in a Bitmask. The VDBE cursor numbers might be
+** spread out over the non-negative integers. For example, the cursor
+** numbers might be 3, 8, 9, 10, 20, 23, 41, and 45. The ExprMaskSet
+** translates these sparse cursor numbers into consecutive integers
+** beginning with 0 in order to make the best possible use of the available
+** bits in the Bitmask. So, in the example above, the cursor numbers
+** would be mapped into integers 0 through 7.
+*/
+typedef struct WhereTerm WhereTerm;
+struct WhereTerm {
+ Expr *pExpr; /* Pointer to the subexpression */
+ i16 iParent; /* Disable pWC->a[iParent] when this term disabled */
+ i16 leftCursor; /* Cursor number of X in "X <op> <expr>" */
+ i16 leftColumn; /* Column number of X in "X <op> <expr>" */
+ u16 eOperator; /* A WO_xx value describing <op> */
+ u8 flags; /* Bit flags. See below */
+ u8 nChild; /* Number of children that must disable us */
+ WhereClause *pWC; /* The clause this term is part of */
+ Bitmask prereqRight; /* Bitmask of tables used by pRight */
+ Bitmask prereqAll; /* Bitmask of tables referenced by p */
+};
+
+/*
+** Allowed values of WhereTerm.flags
+*/
+#define TERM_DYNAMIC 0x01 /* Need to call sqlite3ExprDelete(db, pExpr) */
+#define TERM_VIRTUAL 0x02 /* Added by the optimizer. Do not code */
+#define TERM_CODED 0x04 /* This term is already coded */
+#define TERM_COPIED 0x08 /* Has a child */
+#define TERM_OR_OK 0x10 /* Used during OR-clause processing */
+
+/*
+** An instance of the following structure holds all information about a
+** WHERE clause. Mostly this is a container for one or more WhereTerms.
+*/
+struct WhereClause {
+ Parse *pParse; /* The parser context */
+ ExprMaskSet *pMaskSet; /* Mapping of table indices to bitmasks */
+ int nTerm; /* Number of terms */
+ int nSlot; /* Number of entries in a[] */
+ WhereTerm *a; /* Each a[] describes a term of the WHERE cluase */
+ WhereTerm aStatic[10]; /* Initial static space for a[] */
+};
+
+/*
+** An instance of the following structure keeps track of a mapping
+** between VDBE cursor numbers and bits of the bitmasks in WhereTerm.
+**
+** The VDBE cursor numbers are small integers contained in
+** SrcList_item.iCursor and Expr.iTable fields. For any given WHERE
+** clause, the cursor numbers might not begin with 0 and they might
+** contain gaps in the numbering sequence. But we want to make maximum
+** use of the bits in our bitmasks. This structure provides a mapping
+** from the sparse cursor numbers into consecutive integers beginning
+** with 0.
+**
+** If ExprMaskSet.ix[A]==B it means that The A-th bit of a Bitmask
+** corresponds VDBE cursor number B. The A-th bit of a bitmask is 1<<A.
+**
+** For example, if the WHERE clause expression used these VDBE
+** cursors: 4, 5, 8, 29, 57, 73. Then the ExprMaskSet structure
+** would map those cursor numbers into bits 0 through 5.
+**
+** Note that the mapping is not necessarily ordered. In the example
+** above, the mapping might go like this: 4->3, 5->1, 8->2, 29->0,
+** 57->5, 73->4. Or one of 719 other combinations might be used. It
+** does not really matter. What is important is that sparse cursor
+** numbers all get mapped into bit numbers that begin with 0 and contain
+** no gaps.
+*/
+struct ExprMaskSet {
+ int n; /* Number of assigned cursor values */
+ int ix[sizeof(Bitmask)*8]; /* Cursor assigned to each bit */
+};
+
+
+/*
+** Bitmasks for the operators that indices are able to exploit. An
+** OR-ed combination of these values can be used when searching for
+** terms in the where clause.
+*/
+#define WO_IN 1
+#define WO_EQ 2
+#define WO_LT (WO_EQ<<(TK_LT-TK_EQ))
+#define WO_LE (WO_EQ<<(TK_LE-TK_EQ))
+#define WO_GT (WO_EQ<<(TK_GT-TK_EQ))
+#define WO_GE (WO_EQ<<(TK_GE-TK_EQ))
+#define WO_MATCH 64
+#define WO_ISNULL 128
+
+/*
+** Value for flags returned by bestIndex().
+**
+** The least significant byte is reserved as a mask for WO_ values above.
+** The WhereLevel.flags field is usually set to WO_IN|WO_EQ|WO_ISNULL.
+** But if the table is the right table of a left join, WhereLevel.flags
+** is set to WO_IN|WO_EQ. The WhereLevel.flags field can then be used as
+** the "op" parameter to findTerm when we are resolving equality constraints.
+** ISNULL constraints will then not be used on the right table of a left
+** join. Tickets #2177 and #2189.
+*/
+#define WHERE_ROWID_EQ 0x000100 /* rowid=EXPR or rowid IN (...) */
+#define WHERE_ROWID_RANGE 0x000200 /* rowid<EXPR and/or rowid>EXPR */
+#define WHERE_COLUMN_EQ 0x001000 /* x=EXPR or x IN (...) */
+#define WHERE_COLUMN_RANGE 0x002000 /* x<EXPR and/or x>EXPR */
+#define WHERE_COLUMN_IN 0x004000 /* x IN (...) */
+#define WHERE_TOP_LIMIT 0x010000 /* x<EXPR or x<=EXPR constraint */
+#define WHERE_BTM_LIMIT 0x020000 /* x>EXPR or x>=EXPR constraint */
+#define WHERE_IDX_ONLY 0x080000 /* Use index only - omit table */
+#define WHERE_ORDERBY 0x100000 /* Output will appear in correct order */
+#define WHERE_REVERSE 0x200000 /* Scan in reverse order */
+#define WHERE_UNIQUE 0x400000 /* Selects no more than one row */
+#define WHERE_VIRTUALTABLE 0x800000 /* Use virtual-table processing */
+
+/*
+** Initialize a preallocated WhereClause structure.
+*/
+static void whereClauseInit(
+ WhereClause *pWC, /* The WhereClause to be initialized */
+ Parse *pParse, /* The parsing context */
+ ExprMaskSet *pMaskSet /* Mapping from table indices to bitmasks */
+){
+ pWC->pParse = pParse;
+ pWC->pMaskSet = pMaskSet;
+ pWC->nTerm = 0;
+ pWC->nSlot = ArraySize(pWC->aStatic);
+ pWC->a = pWC->aStatic;
+}
+
+/*
+** Deallocate a WhereClause structure. The WhereClause structure
+** itself is not freed. This routine is the inverse of whereClauseInit().
+*/
+static void whereClauseClear(WhereClause *pWC){
+ int i;
+ WhereTerm *a;
+ sqlite3 *db = pWC->pParse->db;
+ for(i=pWC->nTerm-1, a=pWC->a; i>=0; i--, a++){
+ if( a->flags & TERM_DYNAMIC ){
+ sqlite3ExprDelete(db, a->pExpr);
+ }
+ }
+ if( pWC->a!=pWC->aStatic ){
+ sqlite3DbFree(db, pWC->a);
+ }
+}
+
+/*
+** Add a new entries to the WhereClause structure. Increase the allocated
+** space as necessary.
+**
+** If the flags argument includes TERM_DYNAMIC, then responsibility
+** for freeing the expression p is assumed by the WhereClause object.
+**
+** WARNING: This routine might reallocate the space used to store
+** WhereTerms. All pointers to WhereTerms should be invalidated after
+** calling this routine. Such pointers may be reinitialized by referencing
+** the pWC->a[] array.
+*/
+static int whereClauseInsert(WhereClause *pWC, Expr *p, int flags){
+ WhereTerm *pTerm;
+ int idx;
+ if( pWC->nTerm>=pWC->nSlot ){
+ WhereTerm *pOld = pWC->a;
+ sqlite3 *db = pWC->pParse->db;
+ pWC->a = sqlite3DbMallocRaw(db, sizeof(pWC->a[0])*pWC->nSlot*2 );
+ if( pWC->a==0 ){
+ if( flags & TERM_DYNAMIC ){
+ sqlite3ExprDelete(db, p);
+ }
+ pWC->a = pOld;
+ return 0;
+ }
+ memcpy(pWC->a, pOld, sizeof(pWC->a[0])*pWC->nTerm);
+ if( pOld!=pWC->aStatic ){
+ sqlite3DbFree(db, pOld);
+ }
+ pWC->nSlot *= 2;
+ }
+ pTerm = &pWC->a[idx = pWC->nTerm];
+ pWC->nTerm++;
+ pTerm->pExpr = p;
+ pTerm->flags = flags;
+ pTerm->pWC = pWC;
+ pTerm->iParent = -1;
+ return idx;
+}
+
+/*
+** This routine identifies subexpressions in the WHERE clause where
+** each subexpression is separated by the AND operator or some other
+** operator specified in the op parameter. The WhereClause structure
+** is filled with pointers to subexpressions. For example:
+**
+** WHERE a=='hello' AND coalesce(b,11)<10 AND (c+12!=d OR c==22)
+** \________/ \_______________/ \________________/
+** slot[0] slot[1] slot[2]
+**
+** The original WHERE clause in pExpr is unaltered. All this routine
+** does is make slot[] entries point to substructure within pExpr.
+**
+** In the previous sentence and in the diagram, "slot[]" refers to
+** the WhereClause.a[] array. This array grows as needed to contain
+** all terms of the WHERE clause.
+*/
+static void whereSplit(WhereClause *pWC, Expr *pExpr, int op){
+ if( pExpr==0 ) return;
+ if( pExpr->op!=op ){
+ whereClauseInsert(pWC, pExpr, 0);
+ }else{
+ whereSplit(pWC, pExpr->pLeft, op);
+ whereSplit(pWC, pExpr->pRight, op);
+ }
+}
+
+/*
+** Initialize an expression mask set
+*/
+#define initMaskSet(P) memset(P, 0, sizeof(*P))
+
+/*
+** Return the bitmask for the given cursor number. Return 0 if
+** iCursor is not in the set.
+*/
+static Bitmask getMask(ExprMaskSet *pMaskSet, int iCursor){
+ int i;
+ for(i=0; i<pMaskSet->n; i++){
+ if( pMaskSet->ix[i]==iCursor ){
+ return ((Bitmask)1)<<i;
+ }
+ }
+ return 0;
+}
+
+/*
+** Create a new mask for cursor iCursor.
+**
+** There is one cursor per table in the FROM clause. The number of
+** tables in the FROM clause is limited by a test early in the
+** sqlite3WhereBegin() routine. So we know that the pMaskSet->ix[]
+** array will never overflow.
+*/
+static void createMask(ExprMaskSet *pMaskSet, int iCursor){
+ assert( pMaskSet->n < ArraySize(pMaskSet->ix) );
+ pMaskSet->ix[pMaskSet->n++] = iCursor;
+}
+
+/*
+** This routine walks (recursively) an expression tree and generates
+** a bitmask indicating which tables are used in that expression
+** tree.
+**
+** In order for this routine to work, the calling function must have
+** previously invoked sqlite3ExprResolveNames() on the expression. See
+** the header comment on that routine for additional information.
+** The sqlite3ExprResolveNames() routines looks for column names and
+** sets their opcodes to TK_COLUMN and their Expr.iTable fields to
+** the VDBE cursor number of the table. This routine just has to
+** translate the cursor numbers into bitmask values and OR all
+** the bitmasks together.
+*/
+static Bitmask exprListTableUsage(ExprMaskSet*, ExprList*);
+static Bitmask exprSelectTableUsage(ExprMaskSet*, Select*);
+static Bitmask exprTableUsage(ExprMaskSet *pMaskSet, Expr *p){
+ Bitmask mask = 0;
+ if( p==0 ) return 0;
+ if( p->op==TK_COLUMN ){
+ mask = getMask(pMaskSet, p->iTable);
+ return mask;
+ }
+ mask = exprTableUsage(pMaskSet, p->pRight);
+ mask |= exprTableUsage(pMaskSet, p->pLeft);
+ mask |= exprListTableUsage(pMaskSet, p->pList);
+ mask |= exprSelectTableUsage(pMaskSet, p->pSelect);
+ return mask;
+}
+static Bitmask exprListTableUsage(ExprMaskSet *pMaskSet, ExprList *pList){
+ int i;
+ Bitmask mask = 0;
+ if( pList ){
+ for(i=0; i<pList->nExpr; i++){
+ mask |= exprTableUsage(pMaskSet, pList->a[i].pExpr);
+ }
+ }
+ return mask;
+}
+static Bitmask exprSelectTableUsage(ExprMaskSet *pMaskSet, Select *pS){
+ Bitmask mask = 0;
+ while( pS ){
+ mask |= exprListTableUsage(pMaskSet, pS->pEList);
+ mask |= exprListTableUsage(pMaskSet, pS->pGroupBy);
+ mask |= exprListTableUsage(pMaskSet, pS->pOrderBy);
+ mask |= exprTableUsage(pMaskSet, pS->pWhere);
+ mask |= exprTableUsage(pMaskSet, pS->pHaving);
+ pS = pS->pPrior;
+ }
+ return mask;
+}
+
+/*
+** Return TRUE if the given operator is one of the operators that is
+** allowed for an indexable WHERE clause term. The allowed operators are
+** "=", "<", ">", "<=", ">=", and "IN".
+*/
+static int allowedOp(int op){
+ assert( TK_GT>TK_EQ && TK_GT<TK_GE );
+ assert( TK_LT>TK_EQ && TK_LT<TK_GE );
+ assert( TK_LE>TK_EQ && TK_LE<TK_GE );
+ assert( TK_GE==TK_EQ+4 );
+ return op==TK_IN || (op>=TK_EQ && op<=TK_GE) || op==TK_ISNULL;
+}
+
+/*
+** Swap two objects of type T.
+*/
+#define SWAP(TYPE,A,B) {TYPE t=A; A=B; B=t;}
+
+/*
+** Commute a comparison operator. Expressions of the form "X op Y"
+** are converted into "Y op X".
+**
+** If a collation sequence is associated with either the left or right
+** side of the comparison, it remains associated with the same side after
+** the commutation. So "Y collate NOCASE op X" becomes
+** "X collate NOCASE op Y". This is because any collation sequence on
+** the left hand side of a comparison overrides any collation sequence
+** attached to the right. For the same reason the EP_ExpCollate flag
+** is not commuted.
+*/
+static void exprCommute(Expr *pExpr){
+ u16 expRight = (pExpr->pRight->flags & EP_ExpCollate);
+ u16 expLeft = (pExpr->pLeft->flags & EP_ExpCollate);
+ assert( allowedOp(pExpr->op) && pExpr->op!=TK_IN );
+ SWAP(CollSeq*,pExpr->pRight->pColl,pExpr->pLeft->pColl);
+ pExpr->pRight->flags = (pExpr->pRight->flags & ~EP_ExpCollate) | expLeft;
+ pExpr->pLeft->flags = (pExpr->pLeft->flags & ~EP_ExpCollate) | expRight;
+ SWAP(Expr*,pExpr->pRight,pExpr->pLeft);
+ if( pExpr->op>=TK_GT ){
+ assert( TK_LT==TK_GT+2 );
+ assert( TK_GE==TK_LE+2 );
+ assert( TK_GT>TK_EQ );
+ assert( TK_GT<TK_LE );
+ assert( pExpr->op>=TK_GT && pExpr->op<=TK_GE );
+ pExpr->op = ((pExpr->op-TK_GT)^2)+TK_GT;
+ }
+}
+
+/*
+** Translate from TK_xx operator to WO_xx bitmask.
+*/
+static int operatorMask(int op){
+ int c;
+ assert( allowedOp(op) );
+ if( op==TK_IN ){
+ c = WO_IN;
+ }else if( op==TK_ISNULL ){
+ c = WO_ISNULL;
+ }else{
+ c = WO_EQ<<(op-TK_EQ);
+ }
+ assert( op!=TK_ISNULL || c==WO_ISNULL );
+ assert( op!=TK_IN || c==WO_IN );
+ assert( op!=TK_EQ || c==WO_EQ );
+ assert( op!=TK_LT || c==WO_LT );
+ assert( op!=TK_LE || c==WO_LE );
+ assert( op!=TK_GT || c==WO_GT );
+ assert( op!=TK_GE || c==WO_GE );
+ return c;
+}
+
+/*
+** Search for a term in the WHERE clause that is of the form "X <op> <expr>"
+** where X is a reference to the iColumn of table iCur and <op> is one of
+** the WO_xx operator codes specified by the op parameter.
+** Return a pointer to the term. Return 0 if not found.
+*/
+static WhereTerm *findTerm(
+ WhereClause *pWC, /* The WHERE clause to be searched */
+ int iCur, /* Cursor number of LHS */
+ int iColumn, /* Column number of LHS */
+ Bitmask notReady, /* RHS must not overlap with this mask */
+ u16 op, /* Mask of WO_xx values describing operator */
+ Index *pIdx /* Must be compatible with this index, if not NULL */
+){
+ WhereTerm *pTerm;
+ int k;
+ assert( iCur>=0 );
+ for(pTerm=pWC->a, k=pWC->nTerm; k; k--, pTerm++){
+ if( pTerm->leftCursor==iCur
+ && (pTerm->prereqRight & notReady)==0
+ && pTerm->leftColumn==iColumn
+ && (pTerm->eOperator & op)!=0
+ ){
+ if( pIdx && pTerm->eOperator!=WO_ISNULL ){
+ Expr *pX = pTerm->pExpr;
+ CollSeq *pColl;
+ char idxaff;
+ int j;
+ Parse *pParse = pWC->pParse;
+
+ idxaff = pIdx->pTable->aCol[iColumn].affinity;
+ if( !sqlite3IndexAffinityOk(pX, idxaff) ) continue;
+
+ /* Figure out the collation sequence required from an index for
+ ** it to be useful for optimising expression pX. Store this
+ ** value in variable pColl.
+ */
+ assert(pX->pLeft);
+ pColl = sqlite3BinaryCompareCollSeq(pParse, pX->pLeft, pX->pRight);
+ if( !pColl ){
+ pColl = pParse->db->pDfltColl;
+ }
+
+ for(j=0; pIdx->aiColumn[j]!=iColumn; j++){
+ if( NEVER(j>=pIdx->nColumn) ) return 0;
+ }
+ if( sqlite3StrICmp(pColl->zName, pIdx->azColl[j]) ) continue;
+ }
+ return pTerm;
+ }
+ }
+ return 0;
+}
+
+/* Forward reference */
+static void exprAnalyze(SrcList*, WhereClause*, int);
+
+/*
+** Call exprAnalyze on all terms in a WHERE clause.
+**
+**
+*/
+static void exprAnalyzeAll(
+ SrcList *pTabList, /* the FROM clause */
+ WhereClause *pWC /* the WHERE clause to be analyzed */
+){
+ int i;
+ for(i=pWC->nTerm-1; i>=0; i--){
+ exprAnalyze(pTabList, pWC, i);
+ }
+}
+
+#ifndef SQLITE_OMIT_LIKE_OPTIMIZATION
+/*
+** Check to see if the given expression is a LIKE or GLOB operator that
+** can be optimized using inequality constraints. Return TRUE if it is
+** so and false if not.
+**
+** In order for the operator to be optimizible, the RHS must be a string
+** literal that does not begin with a wildcard.
+*/
+static int isLikeOrGlob(
+ sqlite3 *db, /* The database */
+ Expr *pExpr, /* Test this expression */
+ int *pnPattern, /* Number of non-wildcard prefix characters */
+ int *pisComplete, /* True if the only wildcard is % in the last character */
+ int *pnoCase /* True if uppercase is equivalent to lowercase */
+){
+ const char *z;
+ Expr *pRight, *pLeft;
+ ExprList *pList;
+ int c, cnt;
+ char wc[3];
+ CollSeq *pColl;
+
+ if( !sqlite3IsLikeFunction(db, pExpr, pnoCase, wc) ){
+ return 0;
+ }
+#ifdef SQLITE_EBCDIC
+ if( *pnoCase ) return 0;
+#endif
+ pList = pExpr->pList;
+ pRight = pList->a[0].pExpr;
+ if( pRight->op!=TK_STRING
+ && (pRight->op!=TK_REGISTER || pRight->iColumn!=TK_STRING) ){
+ return 0;
+ }
+ pLeft = pList->a[1].pExpr;
+ if( pLeft->op!=TK_COLUMN ){
+ return 0;
+ }
+ pColl = pLeft->pColl;
+ assert( pColl!=0 || pLeft->iColumn==-1 );
+ if( pColl==0 ){
+ /* No collation is defined for the ROWID. Use the default. */
+ pColl = db->pDfltColl;
+ }
+ if( (pColl->type!=SQLITE_COLL_BINARY || *pnoCase) &&
+ (pColl->type!=SQLITE_COLL_NOCASE || !*pnoCase) ){
+ return 0;
+ }
+ sqlite3DequoteExpr(db, pRight);
+ z = (char *)pRight->token.z;
+ cnt = 0;
+ if( z ){
+ while( (c=z[cnt])!=0 && c!=wc[0] && c!=wc[1] && c!=wc[2] ){ cnt++; }
+ }
+ if( cnt==0 || 255==(u8)z[cnt] ){
+ return 0;
+ }
+ *pisComplete = z[cnt]==wc[0] && z[cnt+1]==0;
+ *pnPattern = cnt;
+ return 1;
+}
+#endif /* SQLITE_OMIT_LIKE_OPTIMIZATION */
+
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/*
+** Check to see if the given expression is of the form
+**
+** column MATCH expr
+**
+** If it is then return TRUE. If not, return FALSE.
+*/
+static int isMatchOfColumn(
+ Expr *pExpr /* Test this expression */
+){
+ ExprList *pList;
+
+ if( pExpr->op!=TK_FUNCTION ){
+ return 0;
+ }
+ if( pExpr->token.n!=5 ||
+ sqlite3StrNICmp((const char*)pExpr->token.z,"match",5)!=0 ){
+ return 0;
+ }
+ pList = pExpr->pList;
+ if( pList->nExpr!=2 ){
+ return 0;
+ }
+ if( pList->a[1].pExpr->op != TK_COLUMN ){
+ return 0;
+ }
+ return 1;
+}
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+/*
+** If the pBase expression originated in the ON or USING clause of
+** a join, then transfer the appropriate markings over to derived.
+*/
+static void transferJoinMarkings(Expr *pDerived, Expr *pBase){
+ pDerived->flags |= pBase->flags & EP_FromJoin;
+ pDerived->iRightJoinTable = pBase->iRightJoinTable;
+}
+
+#if !defined(SQLITE_OMIT_OR_OPTIMIZATION) && !defined(SQLITE_OMIT_SUBQUERY)
+/*
+** Return TRUE if the given term of an OR clause can be converted
+** into an IN clause. The iCursor and iColumn define the left-hand
+** side of the IN clause.
+**
+** The context is that we have multiple OR-connected equality terms
+** like this:
+**
+** a=<expr1> OR a=<expr2> OR b=<expr3> OR ...
+**
+** The pOrTerm input to this routine corresponds to a single term of
+** this OR clause. In order for the term to be a candidate for
+** conversion to an IN operator, the following must be true:
+**
+** * The left-hand side of the term must be the column which
+** is identified by iCursor and iColumn.
+**
+** * If the right-hand side is also a column, then the affinities
+** of both right and left sides must be such that no type
+** conversions are required on the right. (Ticket #2249)
+**
+** If both of these conditions are true, then return true. Otherwise
+** return false.
+*/
+static int orTermIsOptCandidate(WhereTerm *pOrTerm, int iCursor, int iColumn){
+ int affLeft, affRight;
+ assert( pOrTerm->eOperator==WO_EQ );
+ if( pOrTerm->leftCursor!=iCursor ){
+ return 0;
+ }
+ if( pOrTerm->leftColumn!=iColumn ){
+ return 0;
+ }
+ affRight = sqlite3ExprAffinity(pOrTerm->pExpr->pRight);
+ if( affRight==0 ){
+ return 1;
+ }
+ affLeft = sqlite3ExprAffinity(pOrTerm->pExpr->pLeft);
+ if( affRight!=affLeft ){
+ return 0;
+ }
+ return 1;
+}
+
+/*
+** Return true if the given term of an OR clause can be ignored during
+** a check to make sure all OR terms are candidates for optimization.
+** In other words, return true if a call to the orTermIsOptCandidate()
+** above returned false but it is not necessary to disqualify the
+** optimization.
+**
+** Suppose the original OR phrase was this:
+**
+** a=4 OR a=11 OR a=b
+**
+** During analysis, the third term gets flipped around and duplicate
+** so that we are left with this:
+**
+** a=4 OR a=11 OR a=b OR b=a
+**
+** Since the last two terms are duplicates, only one of them
+** has to qualify in order for the whole phrase to qualify. When
+** this routine is called, we know that pOrTerm did not qualify.
+** This routine merely checks to see if pOrTerm has a duplicate that
+** might qualify. If there is a duplicate that has not yet been
+** disqualified, then return true. If there are no duplicates, or
+** the duplicate has also been disqualified, return false.
+*/
+static int orTermHasOkDuplicate(WhereClause *pOr, WhereTerm *pOrTerm){
+ if( pOrTerm->flags & TERM_COPIED ){
+ /* This is the original term. The duplicate is to the left had
+ ** has not yet been analyzed and thus has not yet been disqualified. */
+ return 1;
+ }
+ if( (pOrTerm->flags & TERM_VIRTUAL)!=0
+ && (pOr->a[pOrTerm->iParent].flags & TERM_OR_OK)!=0 ){
+ /* This is a duplicate term. The original qualified so this one
+ ** does not have to. */
+ return 1;
+ }
+ /* This is either a singleton term or else it is a duplicate for
+ ** which the original did not qualify. Either way we are done for. */
+ return 0;
+}
+#endif /* !SQLITE_OMIT_OR_OPTIMIZATION && !SQLITE_OMIT_SUBQUERY */
+
+/*
+** The input to this routine is an WhereTerm structure with only the
+** "pExpr" field filled in. The job of this routine is to analyze the
+** subexpression and populate all the other fields of the WhereTerm
+** structure.
+**
+** If the expression is of the form "<expr> <op> X" it gets commuted
+** to the standard form of "X <op> <expr>". If the expression is of
+** the form "X <op> Y" where both X and Y are columns, then the original
+** expression is unchanged and a new virtual expression of the form
+** "Y <op> X" is added to the WHERE clause and analyzed separately.
+*/
+static void exprAnalyze(
+ SrcList *pSrc, /* the FROM clause */
+ WhereClause *pWC, /* the WHERE clause */
+ int idxTerm /* Index of the term to be analyzed */
+){
+ WhereTerm *pTerm;
+ ExprMaskSet *pMaskSet;
+ Expr *pExpr;
+ Bitmask prereqLeft;
+ Bitmask prereqAll;
+ Bitmask extraRight = 0;
+ int nPattern;
+ int isComplete;
+ int noCase;
+ int op;
+ Parse *pParse = pWC->pParse;
+ sqlite3 *db = pParse->db;
+
+ if( db->mallocFailed ){
+ return;
+ }
+ pTerm = &pWC->a[idxTerm];
+ pMaskSet = pWC->pMaskSet;
+ pExpr = pTerm->pExpr;
+ prereqLeft = exprTableUsage(pMaskSet, pExpr->pLeft);
+ op = pExpr->op;
+ if( op==TK_IN ){
+ assert( pExpr->pRight==0 );
+ pTerm->prereqRight = exprListTableUsage(pMaskSet, pExpr->pList)
+ | exprSelectTableUsage(pMaskSet, pExpr->pSelect);
+ }else if( op==TK_ISNULL ){
+ pTerm->prereqRight = 0;
+ }else{
+ pTerm->prereqRight = exprTableUsage(pMaskSet, pExpr->pRight);
+ }
+ prereqAll = exprTableUsage(pMaskSet, pExpr);
+ if( ExprHasProperty(pExpr, EP_FromJoin) ){
+ Bitmask x = getMask(pMaskSet, pExpr->iRightJoinTable);
+ prereqAll |= x;
+ extraRight = x-1; /* ON clause terms may not be used with an index
+ ** on left table of a LEFT JOIN. Ticket #3015 */
+ }
+ pTerm->prereqAll = prereqAll;
+ pTerm->leftCursor = -1;
+ pTerm->iParent = -1;
+ pTerm->eOperator = 0;
+ if( allowedOp(op) && (pTerm->prereqRight & prereqLeft)==0 ){
+ Expr *pLeft = pExpr->pLeft;
+ Expr *pRight = pExpr->pRight;
+ if( pLeft->op==TK_COLUMN ){
+ pTerm->leftCursor = pLeft->iTable;
+ pTerm->leftColumn = pLeft->iColumn;
+ pTerm->eOperator = operatorMask(op);
+ }
+ if( pRight && pRight->op==TK_COLUMN ){
+ WhereTerm *pNew;
+ Expr *pDup;
+ if( pTerm->leftCursor>=0 ){
+ int idxNew;
+ pDup = sqlite3ExprDup(db, pExpr);
+ if( db->mallocFailed ){
+ sqlite3ExprDelete(db, pDup);
+ return;
+ }
+ idxNew = whereClauseInsert(pWC, pDup, TERM_VIRTUAL|TERM_DYNAMIC);
+ if( idxNew==0 ) return;
+ pNew = &pWC->a[idxNew];
+ pNew->iParent = idxTerm;
+ pTerm = &pWC->a[idxTerm];
+ pTerm->nChild = 1;
+ pTerm->flags |= TERM_COPIED;
+ }else{
+ pDup = pExpr;
+ pNew = pTerm;
+ }
+ exprCommute(pDup);
+ pLeft = pDup->pLeft;
+ pNew->leftCursor = pLeft->iTable;
+ pNew->leftColumn = pLeft->iColumn;
+ pNew->prereqRight = prereqLeft;
+ pNew->prereqAll = prereqAll;
+ pNew->eOperator = operatorMask(pDup->op);
+ }
+ }
+
+#ifndef SQLITE_OMIT_BETWEEN_OPTIMIZATION
+ /* If a term is the BETWEEN operator, create two new virtual terms
+ ** that define the range that the BETWEEN implements.
+ */
+ else if( pExpr->op==TK_BETWEEN ){
+ ExprList *pList = pExpr->pList;
+ int i;
+ static const u8 ops[] = {TK_GE, TK_LE};
+ assert( pList!=0 );
+ assert( pList->nExpr==2 );
+ for(i=0; i<2; i++){
+ Expr *pNewExpr;
+ int idxNew;
+ pNewExpr = sqlite3Expr(db, ops[i], sqlite3ExprDup(db, pExpr->pLeft),
+ sqlite3ExprDup(db, pList->a[i].pExpr), 0);
+ idxNew = whereClauseInsert(pWC, pNewExpr, TERM_VIRTUAL|TERM_DYNAMIC);
+ exprAnalyze(pSrc, pWC, idxNew);
+ pTerm = &pWC->a[idxTerm];
+ pWC->a[idxNew].iParent = idxTerm;
+ }
+ pTerm->nChild = 2;
+ }
+#endif /* SQLITE_OMIT_BETWEEN_OPTIMIZATION */
+
+#if !defined(SQLITE_OMIT_OR_OPTIMIZATION) && !defined(SQLITE_OMIT_SUBQUERY)
+ /* Attempt to convert OR-connected terms into an IN operator so that
+ ** they can make use of indices. Example:
+ **
+ ** x = expr1 OR expr2 = x OR x = expr3
+ **
+ ** is converted into
+ **
+ ** x IN (expr1,expr2,expr3)
+ **
+ ** This optimization must be omitted if OMIT_SUBQUERY is defined because
+ ** the compiler for the the IN operator is part of sub-queries.
+ */
+ else if( pExpr->op==TK_OR ){
+ int ok;
+ int i, j;
+ int iColumn, iCursor;
+ WhereClause sOr;
+ WhereTerm *pOrTerm;
+
+ assert( (pTerm->flags & TERM_DYNAMIC)==0 );
+ whereClauseInit(&sOr, pWC->pParse, pMaskSet);
+ whereSplit(&sOr, pExpr, TK_OR);
+ exprAnalyzeAll(pSrc, &sOr);
+ assert( sOr.nTerm>=2 );
+ j = 0;
+ if( db->mallocFailed ) goto or_not_possible;
+ do{
+ assert( j<sOr.nTerm );
+ iColumn = sOr.a[j].leftColumn;
+ iCursor = sOr.a[j].leftCursor;
+ ok = iCursor>=0;
+ for(i=sOr.nTerm-1, pOrTerm=sOr.a; i>=0 && ok; i--, pOrTerm++){
+ if( pOrTerm->eOperator!=WO_EQ ){
+ goto or_not_possible;
+ }
+ if( orTermIsOptCandidate(pOrTerm, iCursor, iColumn) ){
+ pOrTerm->flags |= TERM_OR_OK;
+ }else if( orTermHasOkDuplicate(&sOr, pOrTerm) ){
+ pOrTerm->flags &= ~TERM_OR_OK;
+ }else{
+ ok = 0;
+ }
+ }
+ }while( !ok && (sOr.a[j++].flags & TERM_COPIED)!=0 && j<2 );
+ if( ok ){
+ ExprList *pList = 0;
+ Expr *pNew, *pDup;
+ Expr *pLeft = 0;
+ for(i=sOr.nTerm-1, pOrTerm=sOr.a; i>=0; i--, pOrTerm++){
+ if( (pOrTerm->flags & TERM_OR_OK)==0 ) continue;
+ pDup = sqlite3ExprDup(db, pOrTerm->pExpr->pRight);
+ pList = sqlite3ExprListAppend(pWC->pParse, pList, pDup, 0);
+ pLeft = pOrTerm->pExpr->pLeft;
+ }
+ assert( pLeft!=0 );
+ pDup = sqlite3ExprDup(db, pLeft);
+ pNew = sqlite3Expr(db, TK_IN, pDup, 0, 0);
+ if( pNew ){
+ int idxNew;
+ transferJoinMarkings(pNew, pExpr);
+ pNew->pList = pList;
+ idxNew = whereClauseInsert(pWC, pNew, TERM_VIRTUAL|TERM_DYNAMIC);
+ exprAnalyze(pSrc, pWC, idxNew);
+ pTerm = &pWC->a[idxTerm];
+ pWC->a[idxNew].iParent = idxTerm;
+ pTerm->nChild = 1;
+ }else{
+ sqlite3ExprListDelete(db, pList);
+ }
+ }
+or_not_possible:
+ whereClauseClear(&sOr);
+ }
+#endif /* SQLITE_OMIT_OR_OPTIMIZATION */
+
+#ifndef SQLITE_OMIT_LIKE_OPTIMIZATION
+ /* Add constraints to reduce the search space on a LIKE or GLOB
+ ** operator.
+ **
+ ** A like pattern of the form "x LIKE 'abc%'" is changed into constraints
+ **
+ ** x>='abc' AND x<'abd' AND x LIKE 'abc%'
+ **
+ ** The last character of the prefix "abc" is incremented to form the
+ ** termination condition "abd".
+ */
+ if( isLikeOrGlob(db, pExpr, &nPattern, &isComplete, &noCase) ){
+ Expr *pLeft, *pRight;
+ Expr *pStr1, *pStr2;
+ Expr *pNewExpr1, *pNewExpr2;
+ int idxNew1, idxNew2;
+
+ pLeft = pExpr->pList->a[1].pExpr;
+ pRight = pExpr->pList->a[0].pExpr;
+ pStr1 = sqlite3PExpr(pParse, TK_STRING, 0, 0, 0);
+ if( pStr1 ){
+ sqlite3TokenCopy(db, &pStr1->token, &pRight->token);
+ pStr1->token.n = nPattern;
+ pStr1->flags = EP_Dequoted;
+ }
+ pStr2 = sqlite3ExprDup(db, pStr1);
+ if( !db->mallocFailed ){
+ u8 c, *pC;
+ assert( pStr2->token.dyn );
+ pC = (u8*)&pStr2->token.z[nPattern-1];
+ c = *pC;
+ if( noCase ){
+ if( c=='@' ) isComplete = 0;
+ c = sqlite3UpperToLower[c];
+ }
+ *pC = c + 1;
+ }
+ pNewExpr1 = sqlite3PExpr(pParse, TK_GE, sqlite3ExprDup(db,pLeft), pStr1, 0);
+ idxNew1 = whereClauseInsert(pWC, pNewExpr1, TERM_VIRTUAL|TERM_DYNAMIC);
+ exprAnalyze(pSrc, pWC, idxNew1);
+ pNewExpr2 = sqlite3PExpr(pParse, TK_LT, sqlite3ExprDup(db,pLeft), pStr2, 0);
+ idxNew2 = whereClauseInsert(pWC, pNewExpr2, TERM_VIRTUAL|TERM_DYNAMIC);
+ exprAnalyze(pSrc, pWC, idxNew2);
+ pTerm = &pWC->a[idxTerm];
+ if( isComplete ){
+ pWC->a[idxNew1].iParent = idxTerm;
+ pWC->a[idxNew2].iParent = idxTerm;
+ pTerm->nChild = 2;
+ }
+ }
+#endif /* SQLITE_OMIT_LIKE_OPTIMIZATION */
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+ /* Add a WO_MATCH auxiliary term to the constraint set if the
+ ** current expression is of the form: column MATCH expr.
+ ** This information is used by the xBestIndex methods of
+ ** virtual tables. The native query optimizer does not attempt
+ ** to do anything with MATCH functions.
+ */
+ if( isMatchOfColumn(pExpr) ){
+ int idxNew;
+ Expr *pRight, *pLeft;
+ WhereTerm *pNewTerm;
+ Bitmask prereqColumn, prereqExpr;
+
+ pRight = pExpr->pList->a[0].pExpr;
+ pLeft = pExpr->pList->a[1].pExpr;
+ prereqExpr = exprTableUsage(pMaskSet, pRight);
+ prereqColumn = exprTableUsage(pMaskSet, pLeft);
+ if( (prereqExpr & prereqColumn)==0 ){
+ Expr *pNewExpr;
+ pNewExpr = sqlite3Expr(db, TK_MATCH, 0, sqlite3ExprDup(db, pRight), 0);
+ idxNew = whereClauseInsert(pWC, pNewExpr, TERM_VIRTUAL|TERM_DYNAMIC);
+ pNewTerm = &pWC->a[idxNew];
+ pNewTerm->prereqRight = prereqExpr;
+ pNewTerm->leftCursor = pLeft->iTable;
+ pNewTerm->leftColumn = pLeft->iColumn;
+ pNewTerm->eOperator = WO_MATCH;
+ pNewTerm->iParent = idxTerm;
+ pTerm = &pWC->a[idxTerm];
+ pTerm->nChild = 1;
+ pTerm->flags |= TERM_COPIED;
+ pNewTerm->prereqAll = pTerm->prereqAll;
+ }
+ }
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+ /* Prevent ON clause terms of a LEFT JOIN from being used to drive
+ ** an index for tables to the left of the join.
+ */
+ pTerm->prereqRight |= extraRight;
+}
+
+/*
+** Return TRUE if any of the expressions in pList->a[iFirst...] contain
+** a reference to any table other than the iBase table.
+*/
+static int referencesOtherTables(
+ ExprList *pList, /* Search expressions in ths list */
+ ExprMaskSet *pMaskSet, /* Mapping from tables to bitmaps */
+ int iFirst, /* Be searching with the iFirst-th expression */
+ int iBase /* Ignore references to this table */
+){
+ Bitmask allowed = ~getMask(pMaskSet, iBase);
+ while( iFirst<pList->nExpr ){
+ if( (exprTableUsage(pMaskSet, pList->a[iFirst++].pExpr)&allowed)!=0 ){
+ return 1;
+ }
+ }
+ return 0;
+}
+
+
+/*
+** This routine decides if pIdx can be used to satisfy the ORDER BY
+** clause. If it can, it returns 1. If pIdx cannot satisfy the
+** ORDER BY clause, this routine returns 0.
+**
+** pOrderBy is an ORDER BY clause from a SELECT statement. pTab is the
+** left-most table in the FROM clause of that same SELECT statement and
+** the table has a cursor number of "base". pIdx is an index on pTab.
+**
+** nEqCol is the number of columns of pIdx that are used as equality
+** constraints. Any of these columns may be missing from the ORDER BY
+** clause and the match can still be a success.
+**
+** All terms of the ORDER BY that match against the index must be either
+** ASC or DESC. (Terms of the ORDER BY clause past the end of a UNIQUE
+** index do not need to satisfy this constraint.) The *pbRev value is
+** set to 1 if the ORDER BY clause is all DESC and it is set to 0 if
+** the ORDER BY clause is all ASC.
+*/
+static int isSortingIndex(
+ Parse *pParse, /* Parsing context */
+ ExprMaskSet *pMaskSet, /* Mapping from table indices to bitmaps */
+ Index *pIdx, /* The index we are testing */
+ int base, /* Cursor number for the table to be sorted */
+ ExprList *pOrderBy, /* The ORDER BY clause */
+ int nEqCol, /* Number of index columns with == constraints */
+ int *pbRev /* Set to 1 if ORDER BY is DESC */
+){
+ int i, j; /* Loop counters */
+ int sortOrder = 0; /* XOR of index and ORDER BY sort direction */
+ int nTerm; /* Number of ORDER BY terms */
+ struct ExprList_item *pTerm; /* A term of the ORDER BY clause */
+ sqlite3 *db = pParse->db;
+
+ assert( pOrderBy!=0 );
+ nTerm = pOrderBy->nExpr;
+ assert( nTerm>0 );
+
+ /* Match terms of the ORDER BY clause against columns of
+ ** the index.
+ **
+ ** Note that indices have pIdx->nColumn regular columns plus
+ ** one additional column containing the rowid. The rowid column
+ ** of the index is also allowed to match against the ORDER BY
+ ** clause.
+ */
+ for(i=j=0, pTerm=pOrderBy->a; j<nTerm && i<=pIdx->nColumn; i++){
+ Expr *pExpr; /* The expression of the ORDER BY pTerm */
+ CollSeq *pColl; /* The collating sequence of pExpr */
+ int termSortOrder; /* Sort order for this term */
+ int iColumn; /* The i-th column of the index. -1 for rowid */
+ int iSortOrder; /* 1 for DESC, 0 for ASC on the i-th index term */
+ const char *zColl; /* Name of the collating sequence for i-th index term */
+
+ pExpr = pTerm->pExpr;
+ if( pExpr->op!=TK_COLUMN || pExpr->iTable!=base ){
+ /* Can not use an index sort on anything that is not a column in the
+ ** left-most table of the FROM clause */
+ break;
+ }
+ pColl = sqlite3ExprCollSeq(pParse, pExpr);
+ if( !pColl ){
+ pColl = db->pDfltColl;
+ }
+ if( i<pIdx->nColumn ){
+ iColumn = pIdx->aiColumn[i];
+ if( iColumn==pIdx->pTable->iPKey ){
+ iColumn = -1;
+ }
+ iSortOrder = pIdx->aSortOrder[i];
+ zColl = pIdx->azColl[i];
+ }else{
+ iColumn = -1;
+ iSortOrder = 0;
+ zColl = pColl->zName;
+ }
+ if( pExpr->iColumn!=iColumn || sqlite3StrICmp(pColl->zName, zColl) ){
+ /* Term j of the ORDER BY clause does not match column i of the index */
+ if( i<nEqCol ){
+ /* If an index column that is constrained by == fails to match an
+ ** ORDER BY term, that is OK. Just ignore that column of the index
+ */
+ continue;
+ }else if( i==pIdx->nColumn ){
+ /* Index column i is the rowid. All other terms match. */
+ break;
+ }else{
+ /* If an index column fails to match and is not constrained by ==
+ ** then the index cannot satisfy the ORDER BY constraint.
+ */
+ return 0;
+ }
+ }
+ assert( pIdx->aSortOrder!=0 );
+ assert( pTerm->sortOrder==0 || pTerm->sortOrder==1 );
+ assert( iSortOrder==0 || iSortOrder==1 );
+ termSortOrder = iSortOrder ^ pTerm->sortOrder;
+ if( i>nEqCol ){
+ if( termSortOrder!=sortOrder ){
+ /* Indices can only be used if all ORDER BY terms past the
+ ** equality constraints are all either DESC or ASC. */
+ return 0;
+ }
+ }else{
+ sortOrder = termSortOrder;
+ }
+ j++;
+ pTerm++;
+ if( iColumn<0 && !referencesOtherTables(pOrderBy, pMaskSet, j, base) ){
+ /* If the indexed column is the primary key and everything matches
+ ** so far and none of the ORDER BY terms to the right reference other
+ ** tables in the join, then we are assured that the index can be used
+ ** to sort because the primary key is unique and so none of the other
+ ** columns will make any difference
+ */
+ j = nTerm;
+ }
+ }
+
+ *pbRev = sortOrder!=0;
+ if( j>=nTerm ){
+ /* All terms of the ORDER BY clause are covered by this index so
+ ** this index can be used for sorting. */
+ return 1;
+ }
+ if( pIdx->onError!=OE_None && i==pIdx->nColumn
+ && !referencesOtherTables(pOrderBy, pMaskSet, j, base) ){
+ /* All terms of this index match some prefix of the ORDER BY clause
+ ** and the index is UNIQUE and no terms on the tail of the ORDER BY
+ ** clause reference other tables in a join. If this is all true then
+ ** the order by clause is superfluous. */
+ return 1;
+ }
+ return 0;
+}
+
+/*
+** Check table to see if the ORDER BY clause in pOrderBy can be satisfied
+** by sorting in order of ROWID. Return true if so and set *pbRev to be
+** true for reverse ROWID and false for forward ROWID order.
+*/
+static int sortableByRowid(
+ int base, /* Cursor number for table to be sorted */
+ ExprList *pOrderBy, /* The ORDER BY clause */
+ ExprMaskSet *pMaskSet, /* Mapping from tables to bitmaps */
+ int *pbRev /* Set to 1 if ORDER BY is DESC */
+){
+ Expr *p;
+
+ assert( pOrderBy!=0 );
+ assert( pOrderBy->nExpr>0 );
+ p = pOrderBy->a[0].pExpr;
+ if( p->op==TK_COLUMN && p->iTable==base && p->iColumn==-1
+ && !referencesOtherTables(pOrderBy, pMaskSet, 1, base) ){
+ *pbRev = pOrderBy->a[0].sortOrder;
+ return 1;
+ }
+ return 0;
+}
+
+/*
+** Prepare a crude estimate of the logarithm of the input value.
+** The results need not be exact. This is only used for estimating
+** the total cost of performing operations with O(logN) or O(NlogN)
+** complexity. Because N is just a guess, it is no great tragedy if
+** logN is a little off.
+*/
+static double estLog(double N){
+ double logN = 1;
+ double x = 10;
+ while( N>x ){
+ logN += 1;
+ x *= 10;
+ }
+ return logN;
+}
+
+/*
+** Two routines for printing the content of an sqlite3_index_info
+** structure. Used for testing and debugging only. If neither
+** SQLITE_TEST or SQLITE_DEBUG are defined, then these routines
+** are no-ops.
+*/
+#if !defined(SQLITE_OMIT_VIRTUALTABLE) && defined(SQLITE_DEBUG)
+static void TRACE_IDX_INPUTS(sqlite3_index_info *p){
+ int i;
+ if( !sqlite3WhereTrace ) return;
+ for(i=0; i<p->nConstraint; i++){
+ sqlite3DebugPrintf(" constraint[%d]: col=%d termid=%d op=%d usabled=%d\n",
+ i,
+ p->aConstraint[i].iColumn,
+ p->aConstraint[i].iTermOffset,
+ p->aConstraint[i].op,
+ p->aConstraint[i].usable);
+ }
+ for(i=0; i<p->nOrderBy; i++){
+ sqlite3DebugPrintf(" orderby[%d]: col=%d desc=%d\n",
+ i,
+ p->aOrderBy[i].iColumn,
+ p->aOrderBy[i].desc);
+ }
+}
+static void TRACE_IDX_OUTPUTS(sqlite3_index_info *p){
+ int i;
+ if( !sqlite3WhereTrace ) return;
+ for(i=0; i<p->nConstraint; i++){
+ sqlite3DebugPrintf(" usage[%d]: argvIdx=%d omit=%d\n",
+ i,
+ p->aConstraintUsage[i].argvIndex,
+ p->aConstraintUsage[i].omit);
+ }
+ sqlite3DebugPrintf(" idxNum=%d\n", p->idxNum);
+ sqlite3DebugPrintf(" idxStr=%s\n", p->idxStr);
+ sqlite3DebugPrintf(" orderByConsumed=%d\n", p->orderByConsumed);
+ sqlite3DebugPrintf(" estimatedCost=%g\n", p->estimatedCost);
+}
+#else
+#define TRACE_IDX_INPUTS(A)
+#define TRACE_IDX_OUTPUTS(A)
+#endif
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+/*
+** Compute the best index for a virtual table.
+**
+** The best index is computed by the xBestIndex method of the virtual
+** table module. This routine is really just a wrapper that sets up
+** the sqlite3_index_info structure that is used to communicate with
+** xBestIndex.
+**
+** In a join, this routine might be called multiple times for the
+** same virtual table. The sqlite3_index_info structure is created
+** and initialized on the first invocation and reused on all subsequent
+** invocations. The sqlite3_index_info structure is also used when
+** code is generated to access the virtual table. The whereInfoDelete()
+** routine takes care of freeing the sqlite3_index_info structure after
+** everybody has finished with it.
+*/
+static double bestVirtualIndex(
+ Parse *pParse, /* The parsing context */
+ WhereClause *pWC, /* The WHERE clause */
+ struct SrcList_item *pSrc, /* The FROM clause term to search */
+ Bitmask notReady, /* Mask of cursors that are not available */
+ ExprList *pOrderBy, /* The order by clause */
+ int orderByUsable, /* True if we can potential sort */
+ sqlite3_index_info **ppIdxInfo /* Index information passed to xBestIndex */
+){
+ Table *pTab = pSrc->pTab;
+ sqlite3_vtab *pVtab = pTab->pVtab;
+ sqlite3_index_info *pIdxInfo;
+ struct sqlite3_index_constraint *pIdxCons;
+ struct sqlite3_index_orderby *pIdxOrderBy;
+ struct sqlite3_index_constraint_usage *pUsage;
+ WhereTerm *pTerm;
+ int i, j;
+ int nOrderBy;
+ int rc;
+
+ /* If the sqlite3_index_info structure has not been previously
+ ** allocated and initialized for this virtual table, then allocate
+ ** and initialize it now
+ */
+ pIdxInfo = *ppIdxInfo;
+ if( pIdxInfo==0 ){
+ WhereTerm *pTerm;
+ int nTerm;
+ WHERETRACE(("Recomputing index info for %s...\n", pTab->zName));
+
+ /* Count the number of possible WHERE clause constraints referring
+ ** to this virtual table */
+ for(i=nTerm=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
+ if( pTerm->leftCursor != pSrc->iCursor ) continue;
+ if( (pTerm->eOperator&(pTerm->eOperator-1))==0 );
+ testcase( pTerm->eOperator==WO_IN );
+ testcase( pTerm->eOperator==WO_ISNULL );
+ if( pTerm->eOperator & (WO_IN|WO_ISNULL) ) continue;
+ nTerm++;
+ }
+
+ /* If the ORDER BY clause contains only columns in the current
+ ** virtual table then allocate space for the aOrderBy part of
+ ** the sqlite3_index_info structure.
+ */
+ nOrderBy = 0;
+ if( pOrderBy ){
+ for(i=0; i<pOrderBy->nExpr; i++){
+ Expr *pExpr = pOrderBy->a[i].pExpr;
+ if( pExpr->op!=TK_COLUMN || pExpr->iTable!=pSrc->iCursor ) break;
+ }
+ if( i==pOrderBy->nExpr ){
+ nOrderBy = pOrderBy->nExpr;
+ }
+ }
+
+ /* Allocate the sqlite3_index_info structure
+ */
+ pIdxInfo = sqlite3DbMallocZero(pParse->db, sizeof(*pIdxInfo)
+ + (sizeof(*pIdxCons) + sizeof(*pUsage))*nTerm
+ + sizeof(*pIdxOrderBy)*nOrderBy );
+ if( pIdxInfo==0 ){
+ sqlite3ErrorMsg(pParse, "out of memory");
+ return 0.0;
+ }
+ *ppIdxInfo = pIdxInfo;
+
+ /* Initialize the structure. The sqlite3_index_info structure contains
+ ** many fields that are declared "const" to prevent xBestIndex from
+ ** changing them. We have to do some funky casting in order to
+ ** initialize those fields.
+ */
+ pIdxCons = (struct sqlite3_index_constraint*)&pIdxInfo[1];
+ pIdxOrderBy = (struct sqlite3_index_orderby*)&pIdxCons[nTerm];
+ pUsage = (struct sqlite3_index_constraint_usage*)&pIdxOrderBy[nOrderBy];
+ *(int*)&pIdxInfo->nConstraint = nTerm;
+ *(int*)&pIdxInfo->nOrderBy = nOrderBy;
+ *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint = pIdxCons;
+ *(struct sqlite3_index_orderby**)&pIdxInfo->aOrderBy = pIdxOrderBy;
+ *(struct sqlite3_index_constraint_usage**)&pIdxInfo->aConstraintUsage =
+ pUsage;
+
+ for(i=j=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
+ if( pTerm->leftCursor != pSrc->iCursor ) continue;
+ if( (pTerm->eOperator&(pTerm->eOperator-1))==0 );
+ testcase( pTerm->eOperator==WO_IN );
+ testcase( pTerm->eOperator==WO_ISNULL );
+ if( pTerm->eOperator & (WO_IN|WO_ISNULL) ) continue;
+ pIdxCons[j].iColumn = pTerm->leftColumn;
+ pIdxCons[j].iTermOffset = i;
+ pIdxCons[j].op = pTerm->eOperator;
+ /* The direct assignment in the previous line is possible only because
+ ** the WO_ and SQLITE_INDEX_CONSTRAINT_ codes are identical. The
+ ** following asserts verify this fact. */
+ assert( WO_EQ==SQLITE_INDEX_CONSTRAINT_EQ );
+ assert( WO_LT==SQLITE_INDEX_CONSTRAINT_LT );
+ assert( WO_LE==SQLITE_INDEX_CONSTRAINT_LE );
+ assert( WO_GT==SQLITE_INDEX_CONSTRAINT_GT );
+ assert( WO_GE==SQLITE_INDEX_CONSTRAINT_GE );
+ assert( WO_MATCH==SQLITE_INDEX_CONSTRAINT_MATCH );
+ assert( pTerm->eOperator & (WO_EQ|WO_LT|WO_LE|WO_GT|WO_GE|WO_MATCH) );
+ j++;
+ }
+ for(i=0; i<nOrderBy; i++){
+ Expr *pExpr = pOrderBy->a[i].pExpr;
+ pIdxOrderBy[i].iColumn = pExpr->iColumn;
+ pIdxOrderBy[i].desc = pOrderBy->a[i].sortOrder;
+ }
+ }
+
+ /* At this point, the sqlite3_index_info structure that pIdxInfo points
+ ** to will have been initialized, either during the current invocation or
+ ** during some prior invocation. Now we just have to customize the
+ ** details of pIdxInfo for the current invocation and pass it to
+ ** xBestIndex.
+ */
+
+ /* The module name must be defined. Also, by this point there must
+ ** be a pointer to an sqlite3_vtab structure. Otherwise
+ ** sqlite3ViewGetColumnNames() would have picked up the error.
+ */
+ assert( pTab->azModuleArg && pTab->azModuleArg[0] );
+ assert( pVtab );
+#if 0
+ if( pTab->pVtab==0 ){
+ sqlite3ErrorMsg(pParse, "undefined module %s for table %s",
+ pTab->azModuleArg[0], pTab->zName);
+ return 0.0;
+ }
+#endif
+
+ /* Set the aConstraint[].usable fields and initialize all
+ ** output variables to zero.
+ **
+ ** aConstraint[].usable is true for constraints where the right-hand
+ ** side contains only references to tables to the left of the current
+ ** table. In other words, if the constraint is of the form:
+ **
+ ** column = expr
+ **
+ ** and we are evaluating a join, then the constraint on column is
+ ** only valid if all tables referenced in expr occur to the left
+ ** of the table containing column.
+ **
+ ** The aConstraints[] array contains entries for all constraints
+ ** on the current table. That way we only have to compute it once
+ ** even though we might try to pick the best index multiple times.
+ ** For each attempt at picking an index, the order of tables in the
+ ** join might be different so we have to recompute the usable flag
+ ** each time.
+ */
+ pIdxCons = *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint;
+ pUsage = pIdxInfo->aConstraintUsage;
+ for(i=0; i<pIdxInfo->nConstraint; i++, pIdxCons++){
+ j = pIdxCons->iTermOffset;
+ pTerm = &pWC->a[j];
+ pIdxCons->usable = (pTerm->prereqRight & notReady)==0;
+ }
+ memset(pUsage, 0, sizeof(pUsage[0])*pIdxInfo->nConstraint);
+ if( pIdxInfo->needToFreeIdxStr ){
+ sqlite3_free(pIdxInfo->idxStr);
+ }
+ pIdxInfo->idxStr = 0;
+ pIdxInfo->idxNum = 0;
+ pIdxInfo->needToFreeIdxStr = 0;
+ pIdxInfo->orderByConsumed = 0;
+ pIdxInfo->estimatedCost = SQLITE_BIG_DBL / 2.0;
+ nOrderBy = pIdxInfo->nOrderBy;
+ if( pIdxInfo->nOrderBy && !orderByUsable ){
+ *(int*)&pIdxInfo->nOrderBy = 0;
+ }
+
+ (void)sqlite3SafetyOff(pParse->db);
+ WHERETRACE(("xBestIndex for %s\n", pTab->zName));
+ TRACE_IDX_INPUTS(pIdxInfo);
+ rc = pVtab->pModule->xBestIndex(pVtab, pIdxInfo);
+ TRACE_IDX_OUTPUTS(pIdxInfo);
+ (void)sqlite3SafetyOn(pParse->db);
+
+ if( rc!=SQLITE_OK ){
+ if( rc==SQLITE_NOMEM ){
+ pParse->db->mallocFailed = 1;
+ }else if( !pVtab->zErrMsg ){
+ sqlite3ErrorMsg(pParse, "%s", sqlite3ErrStr(rc));
+ }else{
+ sqlite3ErrorMsg(pParse, "%s", pVtab->zErrMsg);
+ }
+ }
+ sqlite3DbFree(pParse->db, pVtab->zErrMsg);
+ pVtab->zErrMsg = 0;
+
+ for(i=0; i<pIdxInfo->nConstraint; i++){
+ if( !pIdxInfo->aConstraint[i].usable && pUsage[i].argvIndex>0 ){
+ sqlite3ErrorMsg(pParse,
+ "table %s: xBestIndex returned an invalid plan", pTab->zName);
+ return 0.0;
+ }
+ }
+
+ *(int*)&pIdxInfo->nOrderBy = nOrderBy;
+ return pIdxInfo->estimatedCost;
+}
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+/*
+** Find the best index for accessing a particular table. Return a pointer
+** to the index, flags that describe how the index should be used, the
+** number of equality constraints, and the "cost" for this index.
+**
+** The lowest cost index wins. The cost is an estimate of the amount of
+** CPU and disk I/O need to process the request using the selected index.
+** Factors that influence cost include:
+**
+** * The estimated number of rows that will be retrieved. (The
+** fewer the better.)
+**
+** * Whether or not sorting must occur.
+**
+** * Whether or not there must be separate lookups in the
+** index and in the main table.
+**
+*/
+static double bestIndex(
+ Parse *pParse, /* The parsing context */
+ WhereClause *pWC, /* The WHERE clause */
+ struct SrcList_item *pSrc, /* The FROM clause term to search */
+ Bitmask notReady, /* Mask of cursors that are not available */
+ ExprList *pOrderBy, /* The order by clause */
+ Index **ppIndex, /* Make *ppIndex point to the best index */
+ int *pFlags, /* Put flags describing this choice in *pFlags */
+ int *pnEq /* Put the number of == or IN constraints here */
+){
+ WhereTerm *pTerm;
+ Index *bestIdx = 0; /* Index that gives the lowest cost */
+ double lowestCost; /* The cost of using bestIdx */
+ int bestFlags = 0; /* Flags associated with bestIdx */
+ int bestNEq = 0; /* Best value for nEq */
+ int iCur = pSrc->iCursor; /* The cursor of the table to be accessed */
+ Index *pProbe; /* An index we are evaluating */
+ int rev; /* True to scan in reverse order */
+ int flags; /* Flags associated with pProbe */
+ int nEq; /* Number of == or IN constraints */
+ int eqTermMask; /* Mask of valid equality operators */
+ double cost; /* Cost of using pProbe */
+
+ WHERETRACE(("bestIndex: tbl=%s notReady=%llx\n", pSrc->pTab->zName, notReady));
+ lowestCost = SQLITE_BIG_DBL;
+ pProbe = pSrc->pTab->pIndex;
+
+ /* If the table has no indices and there are no terms in the where
+ ** clause that refer to the ROWID, then we will never be able to do
+ ** anything other than a full table scan on this table. We might as
+ ** well put it first in the join order. That way, perhaps it can be
+ ** referenced by other tables in the join.
+ */
+ if( pProbe==0 &&
+ findTerm(pWC, iCur, -1, 0, WO_EQ|WO_IN|WO_LT|WO_LE|WO_GT|WO_GE,0)==0 &&
+ (pOrderBy==0 || !sortableByRowid(iCur, pOrderBy, pWC->pMaskSet, &rev)) ){
+ *pFlags = 0;
+ *ppIndex = 0;
+ *pnEq = 0;
+ return 0.0;
+ }
+
+ /* Check for a rowid=EXPR or rowid IN (...) constraints
+ */
+ pTerm = findTerm(pWC, iCur, -1, notReady, WO_EQ|WO_IN, 0);
+ if( pTerm ){
+ Expr *pExpr;
+ *ppIndex = 0;
+ bestFlags = WHERE_ROWID_EQ;
+ if( pTerm->eOperator & WO_EQ ){
+ /* Rowid== is always the best pick. Look no further. Because only
+ ** a single row is generated, output is always in sorted order */
+ *pFlags = WHERE_ROWID_EQ | WHERE_UNIQUE;
+ *pnEq = 1;
+ WHERETRACE(("... best is rowid\n"));
+ return 0.0;
+ }else if( (pExpr = pTerm->pExpr)->pList!=0 ){
+ /* Rowid IN (LIST): cost is NlogN where N is the number of list
+ ** elements. */
+ lowestCost = pExpr->pList->nExpr;
+ lowestCost *= estLog(lowestCost);
+ }else{
+ /* Rowid IN (SELECT): cost is NlogN where N is the number of rows
+ ** in the result of the inner select. We have no way to estimate
+ ** that value so make a wild guess. */
+ lowestCost = 200;
+ }
+ WHERETRACE(("... rowid IN cost: %.9g\n", lowestCost));
+ }
+
+ /* Estimate the cost of a table scan. If we do not know how many
+ ** entries are in the table, use 1 million as a guess.
+ */
+ cost = pProbe ? pProbe->aiRowEst[0] : 1000000;
+ WHERETRACE(("... table scan base cost: %.9g\n", cost));
+ flags = WHERE_ROWID_RANGE;
+
+ /* Check for constraints on a range of rowids in a table scan.
+ */
+ pTerm = findTerm(pWC, iCur, -1, notReady, WO_LT|WO_LE|WO_GT|WO_GE, 0);
+ if( pTerm ){
+ if( findTerm(pWC, iCur, -1, notReady, WO_LT|WO_LE, 0) ){
+ flags |= WHERE_TOP_LIMIT;
+ cost /= 3; /* Guess that rowid<EXPR eliminates two-thirds or rows */
+ }
+ if( findTerm(pWC, iCur, -1, notReady, WO_GT|WO_GE, 0) ){
+ flags |= WHERE_BTM_LIMIT;
+ cost /= 3; /* Guess that rowid>EXPR eliminates two-thirds of rows */
+ }
+ WHERETRACE(("... rowid range reduces cost to %.9g\n", cost));
+ }else{
+ flags = 0;
+ }
+
+ /* If the table scan does not satisfy the ORDER BY clause, increase
+ ** the cost by NlogN to cover the expense of sorting. */
+ if( pOrderBy ){
+ if( sortableByRowid(iCur, pOrderBy, pWC->pMaskSet, &rev) ){
+ flags |= WHERE_ORDERBY|WHERE_ROWID_RANGE;
+ if( rev ){
+ flags |= WHERE_REVERSE;
+ }
+ }else{
+ cost += cost*estLog(cost);
+ WHERETRACE(("... sorting increases cost to %.9g\n", cost));
+ }
+ }
+ if( cost<lowestCost ){
+ lowestCost = cost;
+ bestFlags = flags;
+ }
+
+ /* If the pSrc table is the right table of a LEFT JOIN then we may not
+ ** use an index to satisfy IS NULL constraints on that table. This is
+ ** because columns might end up being NULL if the table does not match -
+ ** a circumstance which the index cannot help us discover. Ticket #2177.
+ */
+ if( (pSrc->jointype & JT_LEFT)!=0 ){
+ eqTermMask = WO_EQ|WO_IN;
+ }else{
+ eqTermMask = WO_EQ|WO_IN|WO_ISNULL;
+ }
+
+ /* Look at each index.
+ */
+ for(; pProbe; pProbe=pProbe->pNext){
+ int i; /* Loop counter */
+ double inMultiplier = 1;
+
+ WHERETRACE(("... index %s:\n", pProbe->zName));
+
+ /* Count the number of columns in the index that are satisfied
+ ** by x=EXPR constraints or x IN (...) constraints.
+ */
+ flags = 0;
+ for(i=0; i<pProbe->nColumn; i++){
+ int j = pProbe->aiColumn[i];
+ pTerm = findTerm(pWC, iCur, j, notReady, eqTermMask, pProbe);
+ if( pTerm==0 ) break;
+ flags |= WHERE_COLUMN_EQ;
+ if( pTerm->eOperator & WO_IN ){
+ Expr *pExpr = pTerm->pExpr;
+ flags |= WHERE_COLUMN_IN;
+ if( pExpr->pSelect!=0 ){
+ inMultiplier *= 25;
+ }else if( ALWAYS(pExpr->pList) ){
+ inMultiplier *= pExpr->pList->nExpr + 1;
+ }
+ }
+ }
+ cost = pProbe->aiRowEst[i] * inMultiplier * estLog(inMultiplier);
+ nEq = i;
+ if( pProbe->onError!=OE_None && (flags & WHERE_COLUMN_IN)==0
+ && nEq==pProbe->nColumn ){
+ flags |= WHERE_UNIQUE;
+ }
+ WHERETRACE(("...... nEq=%d inMult=%.9g cost=%.9g\n",nEq,inMultiplier,cost));
+
+ /* Look for range constraints
+ */
+ if( nEq<pProbe->nColumn ){
+ int j = pProbe->aiColumn[nEq];
+ pTerm = findTerm(pWC, iCur, j, notReady, WO_LT|WO_LE|WO_GT|WO_GE, pProbe);
+ if( pTerm ){
+ flags |= WHERE_COLUMN_RANGE;
+ if( findTerm(pWC, iCur, j, notReady, WO_LT|WO_LE, pProbe) ){
+ flags |= WHERE_TOP_LIMIT;
+ cost /= 3;
+ }
+ if( findTerm(pWC, iCur, j, notReady, WO_GT|WO_GE, pProbe) ){
+ flags |= WHERE_BTM_LIMIT;
+ cost /= 3;
+ }
+ WHERETRACE(("...... range reduces cost to %.9g\n", cost));
+ }
+ }
+
+ /* Add the additional cost of sorting if that is a factor.
+ */
+ if( pOrderBy ){
+ if( (flags & WHERE_COLUMN_IN)==0 &&
+ isSortingIndex(pParse,pWC->pMaskSet,pProbe,iCur,pOrderBy,nEq,&rev) ){
+ if( flags==0 ){
+ flags = WHERE_COLUMN_RANGE;
+ }
+ flags |= WHERE_ORDERBY;
+ if( rev ){
+ flags |= WHERE_REVERSE;
+ }
+ }else{
+ cost += cost*estLog(cost);
+ WHERETRACE(("...... orderby increases cost to %.9g\n", cost));
+ }
+ }
+
+ /* Check to see if we can get away with using just the index without
+ ** ever reading the table. If that is the case, then halve the
+ ** cost of this index.
+ */
+ if( flags && pSrc->colUsed < (((Bitmask)1)<<(BMS-1)) ){
+ Bitmask m = pSrc->colUsed;
+ int j;
+ for(j=0; j<pProbe->nColumn; j++){
+ int x = pProbe->aiColumn[j];
+ if( x<BMS-1 ){
+ m &= ~(((Bitmask)1)<<x);
+ }
+ }
+ if( m==0 ){
+ flags |= WHERE_IDX_ONLY;
+ cost /= 2;
+ WHERETRACE(("...... idx-only reduces cost to %.9g\n", cost));
+ }
+ }
+
+ /* If this index has achieved the lowest cost so far, then use it.
+ */
+ if( flags && cost < lowestCost ){
+ bestIdx = pProbe;
+ lowestCost = cost;
+ bestFlags = flags;
+ bestNEq = nEq;
+ }
+ }
+
+ /* Report the best result
+ */
+ *ppIndex = bestIdx;
+ WHERETRACE(("best index is %s, cost=%.9g, flags=%x, nEq=%d\n",
+ bestIdx ? bestIdx->zName : "(none)", lowestCost, bestFlags, bestNEq));
+ *pFlags = bestFlags | eqTermMask;
+ *pnEq = bestNEq;
+ return lowestCost;
+}
+
+
+/*
+** Disable a term in the WHERE clause. Except, do not disable the term
+** if it controls a LEFT OUTER JOIN and it did not originate in the ON
+** or USING clause of that join.
+**
+** Consider the term t2.z='ok' in the following queries:
+**
+** (1) SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.x WHERE t2.z='ok'
+** (2) SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.x AND t2.z='ok'
+** (3) SELECT * FROM t1, t2 WHERE t1.a=t2.x AND t2.z='ok'
+**
+** The t2.z='ok' is disabled in the in (2) because it originates
+** in the ON clause. The term is disabled in (3) because it is not part
+** of a LEFT OUTER JOIN. In (1), the term is not disabled.
+**
+** Disabling a term causes that term to not be tested in the inner loop
+** of the join. Disabling is an optimization. When terms are satisfied
+** by indices, we disable them to prevent redundant tests in the inner
+** loop. We would get the correct results if nothing were ever disabled,
+** but joins might run a little slower. The trick is to disable as much
+** as we can without disabling too much. If we disabled in (1), we'd get
+** the wrong answer. See ticket #813.
+*/
+static void disableTerm(WhereLevel *pLevel, WhereTerm *pTerm){
+ if( pTerm
+ && ALWAYS((pTerm->flags & TERM_CODED)==0)
+ && (pLevel->iLeftJoin==0 || ExprHasProperty(pTerm->pExpr, EP_FromJoin))
+ ){
+ pTerm->flags |= TERM_CODED;
+ if( pTerm->iParent>=0 ){
+ WhereTerm *pOther = &pTerm->pWC->a[pTerm->iParent];
+ if( (--pOther->nChild)==0 ){
+ disableTerm(pLevel, pOther);
+ }
+ }
+ }
+}
+
+/*
+** Apply the affinities associated with the first n columns of index
+** pIdx to the values in the n registers starting at base.
+*/
+static void codeApplyAffinity(Parse *pParse, int base, int n, Index *pIdx){
+ if( n>0 ){
+ Vdbe *v = pParse->pVdbe;
+ assert( v!=0 );
+ sqlite3VdbeAddOp2(v, OP_Affinity, base, n);
+ sqlite3IndexAffinityStr(v, pIdx);
+ sqlite3ExprCacheAffinityChange(pParse, base, n);
+ }
+}
+
+
+/*
+** Generate code for a single equality term of the WHERE clause. An equality
+** term can be either X=expr or X IN (...). pTerm is the term to be
+** coded.
+**
+** The current value for the constraint is left in register iReg.
+**
+** For a constraint of the form X=expr, the expression is evaluated and its
+** result is left on the stack. For constraints of the form X IN (...)
+** this routine sets up a loop that will iterate over all values of X.
+*/
+static int codeEqualityTerm(
+ Parse *pParse, /* The parsing context */
+ WhereTerm *pTerm, /* The term of the WHERE clause to be coded */
+ WhereLevel *pLevel, /* When level of the FROM clause we are working on */
+ int iTarget /* Attempt to leave results in this register */
+){
+ Expr *pX = pTerm->pExpr;
+ Vdbe *v = pParse->pVdbe;
+ int iReg; /* Register holding results */
+
+ if( iTarget<=0 ){
+ iReg = iTarget = sqlite3GetTempReg(pParse);
+ }
+ if( pX->op==TK_EQ ){
+ iReg = sqlite3ExprCodeTarget(pParse, pX->pRight, iTarget);
+ }else if( pX->op==TK_ISNULL ){
+ iReg = iTarget;
+ sqlite3VdbeAddOp2(v, OP_Null, 0, iReg);
+#ifndef SQLITE_OMIT_SUBQUERY
+ }else{
+ int eType;
+ int iTab;
+ struct InLoop *pIn;
+
+ assert( pX->op==TK_IN );
+ iReg = iTarget;
+ eType = sqlite3FindInIndex(pParse, pX, 0);
+ iTab = pX->iTable;
+ sqlite3VdbeAddOp2(v, OP_Rewind, iTab, 0);
+ VdbeComment((v, "%.*s", pX->span.n, pX->span.z));
+ if( pLevel->nIn==0 ){
+ pLevel->nxt = sqlite3VdbeMakeLabel(v);
+ }
+ pLevel->nIn++;
+ pLevel->aInLoop = sqlite3DbReallocOrFree(pParse->db, pLevel->aInLoop,
+ sizeof(pLevel->aInLoop[0])*pLevel->nIn);
+ pIn = pLevel->aInLoop;
+ if( pIn ){
+ pIn += pLevel->nIn - 1;
+ pIn->iCur = iTab;
+ if( eType==IN_INDEX_ROWID ){
+ pIn->topAddr = sqlite3VdbeAddOp2(v, OP_Rowid, iTab, iReg);
+ }else{
+ pIn->topAddr = sqlite3VdbeAddOp3(v, OP_Column, iTab, 0, iReg);
+ }
+ sqlite3VdbeAddOp1(v, OP_IsNull, iReg);
+ }else{
+ pLevel->nIn = 0;
+ }
+#endif
+ }
+ disableTerm(pLevel, pTerm);
+ return iReg;
+}
+
+/*
+** Generate code that will evaluate all == and IN constraints for an
+** index. The values for all constraints are left on the stack.
+**
+** For example, consider table t1(a,b,c,d,e,f) with index i1(a,b,c).
+** Suppose the WHERE clause is this: a==5 AND b IN (1,2,3) AND c>5 AND c<10
+** The index has as many as three equality constraints, but in this
+** example, the third "c" value is an inequality. So only two
+** constraints are coded. This routine will generate code to evaluate
+** a==5 and b IN (1,2,3). The current values for a and b will be left
+** on the stack - a is the deepest and b the shallowest.
+**
+** In the example above nEq==2. But this subroutine works for any value
+** of nEq including 0. If nEq==0, this routine is nearly a no-op.
+** The only thing it does is allocate the pLevel->iMem memory cell.
+**
+** This routine always allocates at least one memory cell and puts
+** the address of that memory cell in pLevel->iMem. The code that
+** calls this routine will use pLevel->iMem to store the termination
+** key value of the loop. If one or more IN operators appear, then
+** this routine allocates an additional nEq memory cells for internal
+** use.
+*/
+static int codeAllEqualityTerms(
+ Parse *pParse, /* Parsing context */
+ WhereLevel *pLevel, /* Which nested loop of the FROM we are coding */
+ WhereClause *pWC, /* The WHERE clause */
+ Bitmask notReady, /* Which parts of FROM have not yet been coded */
+ int nExtraReg /* Number of extra registers to allocate */
+){
+ int nEq = pLevel->nEq; /* The number of == or IN constraints to code */
+ Vdbe *v = pParse->pVdbe; /* The virtual machine under construction */
+ Index *pIdx = pLevel->pIdx; /* The index being used for this loop */
+ int iCur = pLevel->iTabCur; /* The cursor of the table */
+ WhereTerm *pTerm; /* A single constraint term */
+ int j; /* Loop counter */
+ int regBase; /* Base register */
+
+ /* Figure out how many memory cells we will need then allocate them.
+ ** We always need at least one used to store the loop terminator
+ ** value. If there are IN operators we'll need one for each == or
+ ** IN constraint.
+ */
+ pLevel->iMem = pParse->nMem + 1;
+ regBase = pParse->nMem + 2;
+ pParse->nMem += pLevel->nEq + 2 + nExtraReg;
+
+ /* Evaluate the equality constraints
+ */
+ assert( pIdx->nColumn>=nEq );
+ for(j=0; j<nEq; j++){
+ int r1;
+ int k = pIdx->aiColumn[j];
+ pTerm = findTerm(pWC, iCur, k, notReady, pLevel->flags, pIdx);
+ if( NEVER(pTerm==0) ) break;
+ assert( (pTerm->flags & TERM_CODED)==0 );
+ r1 = codeEqualityTerm(pParse, pTerm, pLevel, regBase+j);
+ if( r1!=regBase+j ){
+ sqlite3VdbeAddOp2(v, OP_SCopy, r1, regBase+j);
+ }
+ testcase( pTerm->eOperator & WO_ISNULL );
+ testcase( pTerm->eOperator & WO_IN );
+ if( (pTerm->eOperator & (WO_ISNULL|WO_IN))==0 ){
+ sqlite3VdbeAddOp2(v, OP_IsNull, regBase+j, pLevel->brk);
+ }
+ }
+ return regBase;
+}
+
+#if defined(SQLITE_TEST)
+/*
+** The following variable holds a text description of query plan generated
+** by the most recent call to sqlite3WhereBegin(). Each call to WhereBegin
+** overwrites the previous. This information is used for testing and
+** analysis only.
+*/
+char sqlite3_query_plan[BMS*2*40]; /* Text of the join */
+static int nQPlan = 0; /* Next free slow in _query_plan[] */
+
+#endif /* SQLITE_TEST */
+
+
+/*
+** Free a WhereInfo structure
+*/
+static void whereInfoFree(WhereInfo *pWInfo){
+ if( pWInfo ){
+ int i;
+ sqlite3 *db = pWInfo->pParse->db;
+ for(i=0; i<pWInfo->nLevel; i++){
+ sqlite3_index_info *pInfo = pWInfo->a[i].pIdxInfo;
+ if( pInfo ){
+ assert( pInfo->needToFreeIdxStr==0 );
+ sqlite3DbFree(db, pInfo);
+ }
+ }
+ sqlite3DbFree(db, pWInfo);
+ }
+}
+
+
+/*
+** Generate the beginning of the loop used for WHERE clause processing.
+** The return value is a pointer to an opaque structure that contains
+** information needed to terminate the loop. Later, the calling routine
+** should invoke sqlite3WhereEnd() with the return value of this function
+** in order to complete the WHERE clause processing.
+**
+** If an error occurs, this routine returns NULL.
+**
+** The basic idea is to do a nested loop, one loop for each table in
+** the FROM clause of a select. (INSERT and UPDATE statements are the
+** same as a SELECT with only a single table in the FROM clause.) For
+** example, if the SQL is this:
+**
+** SELECT * FROM t1, t2, t3 WHERE ...;
+**
+** Then the code generated is conceptually like the following:
+**
+** foreach row1 in t1 do \ Code generated
+** foreach row2 in t2 do |-- by sqlite3WhereBegin()
+** foreach row3 in t3 do /
+** ...
+** end \ Code generated
+** end |-- by sqlite3WhereEnd()
+** end /
+**
+** Note that the loops might not be nested in the order in which they
+** appear in the FROM clause if a different order is better able to make
+** use of indices. Note also that when the IN operator appears in
+** the WHERE clause, it might result in additional nested loops for
+** scanning through all values on the right-hand side of the IN.
+**
+** There are Btree cursors associated with each table. t1 uses cursor
+** number pTabList->a[0].iCursor. t2 uses the cursor pTabList->a[1].iCursor.
+** And so forth. This routine generates code to open those VDBE cursors
+** and sqlite3WhereEnd() generates the code to close them.
+**
+** The code that sqlite3WhereBegin() generates leaves the cursors named
+** in pTabList pointing at their appropriate entries. The [...] code
+** can use OP_Column and OP_Rowid opcodes on these cursors to extract
+** data from the various tables of the loop.
+**
+** If the WHERE clause is empty, the foreach loops must each scan their
+** entire tables. Thus a three-way join is an O(N^3) operation. But if
+** the tables have indices and there are terms in the WHERE clause that
+** refer to those indices, a complete table scan can be avoided and the
+** code will run much faster. Most of the work of this routine is checking
+** to see if there are indices that can be used to speed up the loop.
+**
+** Terms of the WHERE clause are also used to limit which rows actually
+** make it to the "..." in the middle of the loop. After each "foreach",
+** terms of the WHERE clause that use only terms in that loop and outer
+** loops are evaluated and if false a jump is made around all subsequent
+** inner loops (or around the "..." if the test occurs within the inner-
+** most loop)
+**
+** OUTER JOINS
+**
+** An outer join of tables t1 and t2 is conceptally coded as follows:
+**
+** foreach row1 in t1 do
+** flag = 0
+** foreach row2 in t2 do
+** start:
+** ...
+** flag = 1
+** end
+** if flag==0 then
+** move the row2 cursor to a null row
+** goto start
+** fi
+** end
+**
+** ORDER BY CLAUSE PROCESSING
+**
+** *ppOrderBy is a pointer to the ORDER BY clause of a SELECT statement,
+** if there is one. If there is no ORDER BY clause or if this routine
+** is called from an UPDATE or DELETE statement, then ppOrderBy is NULL.
+**
+** If an index can be used so that the natural output order of the table
+** scan is correct for the ORDER BY clause, then that index is used and
+** *ppOrderBy is set to NULL. This is an optimization that prevents an
+** unnecessary sort of the result set if an index appropriate for the
+** ORDER BY clause already exists.
+**
+** If the where clause loops cannot be arranged to provide the correct
+** output order, then the *ppOrderBy is unchanged.
+*/
+WhereInfo *sqlite3WhereBegin(
+ Parse *pParse, /* The parser context */
+ SrcList *pTabList, /* A list of all tables to be scanned */
+ Expr *pWhere, /* The WHERE clause */
+ ExprList **ppOrderBy, /* An ORDER BY clause, or NULL */
+ u8 wflags /* One of the WHERE_* flags defined in sqliteInt.h */
+){
+ int i; /* Loop counter */
+ WhereInfo *pWInfo; /* Will become the return value of this function */
+ Vdbe *v = pParse->pVdbe; /* The virtual database engine */
+ int brk, cont = 0; /* Addresses used during code generation */
+ Bitmask notReady; /* Cursors that are not yet positioned */
+ WhereTerm *pTerm; /* A single term in the WHERE clause */
+ ExprMaskSet maskSet; /* The expression mask set */
+ WhereClause wc; /* The WHERE clause is divided into these terms */
+ struct SrcList_item *pTabItem; /* A single entry from pTabList */
+ WhereLevel *pLevel; /* A single level in the pWInfo list */
+ int iFrom; /* First unused FROM clause element */
+ int andFlags; /* AND-ed combination of all wc.a[].flags */
+ sqlite3 *db; /* Database connection */
+ ExprList *pOrderBy = 0;
+
+ /* The number of tables in the FROM clause is limited by the number of
+ ** bits in a Bitmask
+ */
+ if( pTabList->nSrc>BMS ){
+ sqlite3ErrorMsg(pParse, "at most %d tables in a join", BMS);
+ return 0;
+ }
+
+ if( ppOrderBy ){
+ pOrderBy = *ppOrderBy;
+ }
+
+ /* Split the WHERE clause into separate subexpressions where each
+ ** subexpression is separated by an AND operator.
+ */
+ initMaskSet(&maskSet);
+ whereClauseInit(&wc, pParse, &maskSet);
+ sqlite3ExprCodeConstants(pParse, pWhere);
+ whereSplit(&wc, pWhere, TK_AND);
+
+ /* Allocate and initialize the WhereInfo structure that will become the
+ ** return value.
+ */
+ db = pParse->db;
+ pWInfo = sqlite3DbMallocZero(db,
+ sizeof(WhereInfo) + pTabList->nSrc*sizeof(WhereLevel));
+ if( db->mallocFailed ){
+ goto whereBeginNoMem;
+ }
+ pWInfo->nLevel = pTabList->nSrc;
+ pWInfo->pParse = pParse;
+ pWInfo->pTabList = pTabList;
+ pWInfo->iBreak = sqlite3VdbeMakeLabel(v);
+
+ /* Special case: a WHERE clause that is constant. Evaluate the
+ ** expression and either jump over all of the code or fall thru.
+ */
+ if( pWhere && (pTabList->nSrc==0 || sqlite3ExprIsConstantNotJoin(pWhere)) ){
+ sqlite3ExprIfFalse(pParse, pWhere, pWInfo->iBreak, SQLITE_JUMPIFNULL);
+ pWhere = 0;
+ }
+
+ /* Assign a bit from the bitmask to every term in the FROM clause.
+ **
+ ** When assigning bitmask values to FROM clause cursors, it must be
+ ** the case that if X is the bitmask for the N-th FROM clause term then
+ ** the bitmask for all FROM clause terms to the left of the N-th term
+ ** is (X-1). An expression from the ON clause of a LEFT JOIN can use
+ ** its Expr.iRightJoinTable value to find the bitmask of the right table
+ ** of the join. Subtracting one from the right table bitmask gives a
+ ** bitmask for all tables to the left of the join. Knowing the bitmask
+ ** for all tables to the left of a left join is important. Ticket #3015.
+ */
+ for(i=0; i<pTabList->nSrc; i++){
+ createMask(&maskSet, pTabList->a[i].iCursor);
+ }
+#ifndef NDEBUG
+ {
+ Bitmask toTheLeft = 0;
+ for(i=0; i<pTabList->nSrc; i++){
+ Bitmask m = getMask(&maskSet, pTabList->a[i].iCursor);
+ assert( (m-1)==toTheLeft );
+ toTheLeft |= m;
+ }
+ }
+#endif
+
+ /* Analyze all of the subexpressions. Note that exprAnalyze() might
+ ** add new virtual terms onto the end of the WHERE clause. We do not
+ ** want to analyze these virtual terms, so start analyzing at the end
+ ** and work forward so that the added virtual terms are never processed.
+ */
+ exprAnalyzeAll(pTabList, &wc);
+ if( db->mallocFailed ){
+ goto whereBeginNoMem;
+ }
+
+ /* Chose the best index to use for each table in the FROM clause.
+ **
+ ** This loop fills in the following fields:
+ **
+ ** pWInfo->a[].pIdx The index to use for this level of the loop.
+ ** pWInfo->a[].flags WHERE_xxx flags associated with pIdx
+ ** pWInfo->a[].nEq The number of == and IN constraints
+ ** pWInfo->a[].iFrom When term of the FROM clause is being coded
+ ** pWInfo->a[].iTabCur The VDBE cursor for the database table
+ ** pWInfo->a[].iIdxCur The VDBE cursor for the index
+ **
+ ** This loop also figures out the nesting order of tables in the FROM
+ ** clause.
+ */
+ notReady = ~(Bitmask)0;
+ pTabItem = pTabList->a;
+ pLevel = pWInfo->a;
+ andFlags = ~0;
+ WHERETRACE(("*** Optimizer Start ***\n"));
+ for(i=iFrom=0, pLevel=pWInfo->a; i<pTabList->nSrc; i++, pLevel++){
+ Index *pIdx; /* Index for FROM table at pTabItem */
+ int flags; /* Flags asssociated with pIdx */
+ int nEq; /* Number of == or IN constraints */
+ double cost; /* The cost for pIdx */
+ int j; /* For looping over FROM tables */
+ Index *pBest = 0; /* The best index seen so far */
+ int bestFlags = 0; /* Flags associated with pBest */
+ int bestNEq = 0; /* nEq associated with pBest */
+ double lowestCost; /* Cost of the pBest */
+ int bestJ = 0; /* The value of j */
+ Bitmask m; /* Bitmask value for j or bestJ */
+ int once = 0; /* True when first table is seen */
+ sqlite3_index_info *pIndex; /* Current virtual index */
+
+ lowestCost = SQLITE_BIG_DBL;
+ for(j=iFrom, pTabItem=&pTabList->a[j]; j<pTabList->nSrc; j++, pTabItem++){
+ int doNotReorder; /* True if this table should not be reordered */
+
+ doNotReorder = (pTabItem->jointype & (JT_LEFT|JT_CROSS))!=0;
+ if( once && doNotReorder ) break;
+ m = getMask(&maskSet, pTabItem->iCursor);
+ if( (m & notReady)==0 ){
+ if( j==iFrom ) iFrom++;
+ continue;
+ }
+ assert( pTabItem->pTab );
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+ if( IsVirtual(pTabItem->pTab) ){
+ sqlite3_index_info **ppIdxInfo = &pWInfo->a[j].pIdxInfo;
+ cost = bestVirtualIndex(pParse, &wc, pTabItem, notReady,
+ ppOrderBy ? *ppOrderBy : 0, i==0,
+ ppIdxInfo);
+ flags = WHERE_VIRTUALTABLE;
+ pIndex = *ppIdxInfo;
+ if( pIndex && pIndex->orderByConsumed ){
+ flags = WHERE_VIRTUALTABLE | WHERE_ORDERBY;
+ }
+ pIdx = 0;
+ nEq = 0;
+ if( (SQLITE_BIG_DBL/2.0)<cost ){
+ /* The cost is not allowed to be larger than SQLITE_BIG_DBL (the
+ ** inital value of lowestCost in this loop. If it is, then
+ ** the (cost<lowestCost) test below will never be true and
+ ** pLevel->pBestIdx never set.
+ */
+ cost = (SQLITE_BIG_DBL/2.0);
+ }
+ }else
+#endif
+ {
+ cost = bestIndex(pParse, &wc, pTabItem, notReady,
+ (i==0 && ppOrderBy) ? *ppOrderBy : 0,
+ &pIdx, &flags, &nEq);
+ pIndex = 0;
+ }
+ if( cost<lowestCost ){
+ once = 1;
+ lowestCost = cost;
+ pBest = pIdx;
+ bestFlags = flags;
+ bestNEq = nEq;
+ bestJ = j;
+ pLevel->pBestIdx = pIndex;
+ }
+ if( doNotReorder ) break;
+ }
+ WHERETRACE(("*** Optimizer selects table %d for loop %d\n", bestJ,
+ pLevel-pWInfo->a));
+ if( (bestFlags & WHERE_ORDERBY)!=0 ){
+ *ppOrderBy = 0;
+ }
+ andFlags &= bestFlags;
+ pLevel->flags = bestFlags;
+ pLevel->pIdx = pBest;
+ pLevel->nEq = bestNEq;
+ pLevel->aInLoop = 0;
+ pLevel->nIn = 0;
+ if( pBest ){
+ pLevel->iIdxCur = pParse->nTab++;
+ }else{
+ pLevel->iIdxCur = -1;
+ }
+ notReady &= ~getMask(&maskSet, pTabList->a[bestJ].iCursor);
+ pLevel->iFrom = bestJ;
+ }
+ WHERETRACE(("*** Optimizer Finished ***\n"));
+
+ /* If the total query only selects a single row, then the ORDER BY
+ ** clause is irrelevant.
+ */
+ if( (andFlags & WHERE_UNIQUE)!=0 && ppOrderBy ){
+ *ppOrderBy = 0;
+ }
+
+ /* If the caller is an UPDATE or DELETE statement that is requesting
+ ** to use a one-pass algorithm, determine if this is appropriate.
+ ** The one-pass algorithm only works if the WHERE clause constraints
+ ** the statement to update a single row.
+ */
+ assert( (wflags & WHERE_ONEPASS_DESIRED)==0 || pWInfo->nLevel==1 );
+ if( (wflags & WHERE_ONEPASS_DESIRED)!=0 && (andFlags & WHERE_UNIQUE)!=0 ){
+ pWInfo->okOnePass = 1;
+ pWInfo->a[0].flags &= ~WHERE_IDX_ONLY;
+ }
+
+ /* Open all tables in the pTabList and any indices selected for
+ ** searching those tables.
+ */
+ sqlite3CodeVerifySchema(pParse, -1); /* Insert the cookie verifier Goto */
+ for(i=0, pLevel=pWInfo->a; i<pTabList->nSrc; i++, pLevel++){
+ Table *pTab; /* Table to open */
+ Index *pIx; /* Index used to access pTab (if any) */
+ int iDb; /* Index of database containing table/index */
+ int iIdxCur = pLevel->iIdxCur;
+
+#ifndef SQLITE_OMIT_EXPLAIN
+ if( pParse->explain==2 ){
+ char *zMsg;
+ struct SrcList_item *pItem = &pTabList->a[pLevel->iFrom];
+ zMsg = sqlite3MPrintf(db, "TABLE %s", pItem->zName);
+ if( pItem->zAlias ){
+ zMsg = sqlite3MAppendf(db, zMsg, "%s AS %s", zMsg, pItem->zAlias);
+ }
+ if( (pIx = pLevel->pIdx)!=0 ){
+ zMsg = sqlite3MAppendf(db, zMsg, "%s WITH INDEX %s", zMsg, pIx->zName);
+ }else if( pLevel->flags & (WHERE_ROWID_EQ|WHERE_ROWID_RANGE) ){
+ zMsg = sqlite3MAppendf(db, zMsg, "%s USING PRIMARY KEY", zMsg);
+ }
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+ else if( pLevel->pBestIdx ){
+ sqlite3_index_info *pBestIdx = pLevel->pBestIdx;
+ zMsg = sqlite3MAppendf(db, zMsg, "%s VIRTUAL TABLE INDEX %d:%s", zMsg,
+ pBestIdx->idxNum, pBestIdx->idxStr);
+ }
+#endif
+ if( pLevel->flags & WHERE_ORDERBY ){
+ zMsg = sqlite3MAppendf(db, zMsg, "%s ORDER BY", zMsg);
+ }
+ sqlite3VdbeAddOp4(v, OP_Explain, i, pLevel->iFrom, 0, zMsg, P4_DYNAMIC);
+ }
+#endif /* SQLITE_OMIT_EXPLAIN */
+ pTabItem = &pTabList->a[pLevel->iFrom];
+ pTab = pTabItem->pTab;
+ iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
+ if( pTab->isEphem || pTab->pSelect ) continue;
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+ if( pLevel->pBestIdx ){
+ int iCur = pTabItem->iCursor;
+ sqlite3VdbeAddOp4(v, OP_VOpen, iCur, 0, 0,
+ (const char*)pTab->pVtab, P4_VTAB);
+ }else
+#endif
+ if( (pLevel->flags & WHERE_IDX_ONLY)==0 ){
+ int op = pWInfo->okOnePass ? OP_OpenWrite : OP_OpenRead;
+ sqlite3OpenTable(pParse, pTabItem->iCursor, iDb, pTab, op);
+ if( !pWInfo->okOnePass && pTab->nCol<(sizeof(Bitmask)*8) ){
+ Bitmask b = pTabItem->colUsed;
+ int n = 0;
+ for(; b; b=b>>1, n++){}
+ sqlite3VdbeChangeP2(v, sqlite3VdbeCurrentAddr(v)-2, n);
+ assert( n<=pTab->nCol );
+ }
+ }else{
+ sqlite3TableLock(pParse, iDb, pTab->tnum, 0, pTab->zName);
+ }
+ pLevel->iTabCur = pTabItem->iCursor;
+ if( (pIx = pLevel->pIdx)!=0 ){
+ KeyInfo *pKey = sqlite3IndexKeyinfo(pParse, pIx);
+ assert( pIx->pSchema==pTab->pSchema );
+ sqlite3VdbeAddOp2(v, OP_SetNumColumns, 0, pIx->nColumn+1);
+ sqlite3VdbeAddOp4(v, OP_OpenRead, iIdxCur, pIx->tnum, iDb,
+ (char*)pKey, P4_KEYINFO_HANDOFF);
+ VdbeComment((v, "%s", pIx->zName));
+ }
+ sqlite3CodeVerifySchema(pParse, iDb);
+ }
+ pWInfo->iTop = sqlite3VdbeCurrentAddr(v);
+
+ /* Generate the code to do the search. Each iteration of the for
+ ** loop below generates code for a single nested loop of the VM
+ ** program.
+ */
+ notReady = ~(Bitmask)0;
+ for(i=0, pLevel=pWInfo->a; i<pTabList->nSrc; i++, pLevel++){
+ int j;
+ int iCur = pTabItem->iCursor; /* The VDBE cursor for the table */
+ Index *pIdx; /* The index we will be using */
+ int nxt; /* Where to jump to continue with the next IN case */
+ int iIdxCur; /* The VDBE cursor for the index */
+ int omitTable; /* True if we use the index only */
+ int bRev; /* True if we need to scan in reverse order */
+
+ pTabItem = &pTabList->a[pLevel->iFrom];
+ iCur = pTabItem->iCursor;
+ pIdx = pLevel->pIdx;
+ iIdxCur = pLevel->iIdxCur;
+ bRev = (pLevel->flags & WHERE_REVERSE)!=0;
+ omitTable = (pLevel->flags & WHERE_IDX_ONLY)!=0;
+
+ /* Create labels for the "break" and "continue" instructions
+ ** for the current loop. Jump to brk to break out of a loop.
+ ** Jump to cont to go immediately to the next iteration of the
+ ** loop.
+ **
+ ** When there is an IN operator, we also have a "nxt" label that
+ ** means to continue with the next IN value combination. When
+ ** there are no IN operators in the constraints, the "nxt" label
+ ** is the same as "brk".
+ */
+ brk = pLevel->brk = pLevel->nxt = sqlite3VdbeMakeLabel(v);
+ cont = pLevel->cont = sqlite3VdbeMakeLabel(v);
+
+ /* If this is the right table of a LEFT OUTER JOIN, allocate and
+ ** initialize a memory cell that records if this table matches any
+ ** row of the left table of the join.
+ */
+ if( pLevel->iFrom>0 && (pTabItem[0].jointype & JT_LEFT)!=0 ){
+ pLevel->iLeftJoin = ++pParse->nMem;
+ sqlite3VdbeAddOp2(v, OP_Integer, 0, pLevel->iLeftJoin);
+ VdbeComment((v, "init LEFT JOIN no-match flag"));
+ }
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+ if( pLevel->pBestIdx ){
+ /* Case 0: The table is a virtual-table. Use the VFilter and VNext
+ ** to access the data.
+ */
+ int j;
+ int iReg; /* P3 Value for OP_VFilter */
+ sqlite3_index_info *pBestIdx = pLevel->pBestIdx;
+ int nConstraint = pBestIdx->nConstraint;
+ struct sqlite3_index_constraint_usage *aUsage =
+ pBestIdx->aConstraintUsage;
+ const struct sqlite3_index_constraint *aConstraint =
+ pBestIdx->aConstraint;
+
+ iReg = sqlite3GetTempRange(pParse, nConstraint+2);
+ pParse->disableColCache++;
+ for(j=1; j<=nConstraint; j++){
+ int k;
+ for(k=0; k<nConstraint; k++){
+ if( aUsage[k].argvIndex==j ){
+ int iTerm = aConstraint[k].iTermOffset;
+ assert( pParse->disableColCache );
+ sqlite3ExprCode(pParse, wc.a[iTerm].pExpr->pRight, iReg+j+1);
+ break;
+ }
+ }
+ if( k==nConstraint ) break;
+ }
+ assert( pParse->disableColCache );
+ pParse->disableColCache--;
+ sqlite3VdbeAddOp2(v, OP_Integer, pBestIdx->idxNum, iReg);
+ sqlite3VdbeAddOp2(v, OP_Integer, j-1, iReg+1);
+ sqlite3VdbeAddOp4(v, OP_VFilter, iCur, brk, iReg, pBestIdx->idxStr,
+ pBestIdx->needToFreeIdxStr ? P4_MPRINTF : P4_STATIC);
+ sqlite3ReleaseTempRange(pParse, iReg, nConstraint+2);
+ pBestIdx->needToFreeIdxStr = 0;
+ for(j=0; j<nConstraint; j++){
+ if( aUsage[j].omit ){
+ int iTerm = aConstraint[j].iTermOffset;
+ disableTerm(pLevel, &wc.a[iTerm]);
+ }
+ }
+ pLevel->op = OP_VNext;
+ pLevel->p1 = iCur;
+ pLevel->p2 = sqlite3VdbeCurrentAddr(v);
+ }else
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+ if( pLevel->flags & WHERE_ROWID_EQ ){
+ /* Case 1: We can directly reference a single row using an
+ ** equality comparison against the ROWID field. Or
+ ** we reference multiple rows using a "rowid IN (...)"
+ ** construct.
+ */
+ int r1;
+ pTerm = findTerm(&wc, iCur, -1, notReady, WO_EQ|WO_IN, 0);
+ assert( pTerm!=0 );
+ assert( pTerm->pExpr!=0 );
+ assert( pTerm->leftCursor==iCur );
+ assert( omitTable==0 );
+ r1 = codeEqualityTerm(pParse, pTerm, pLevel, 0);
+ nxt = pLevel->nxt;
+ sqlite3VdbeAddOp2(v, OP_MustBeInt, r1, nxt);
+ sqlite3VdbeAddOp3(v, OP_NotExists, iCur, nxt, r1);
+ VdbeComment((v, "pk"));
+ pLevel->op = OP_Noop;
+ }else if( pLevel->flags & WHERE_ROWID_RANGE ){
+ /* Case 2: We have an inequality comparison against the ROWID field.
+ */
+ int testOp = OP_Noop;
+ int start;
+ WhereTerm *pStart, *pEnd;
+
+ assert( omitTable==0 );
+ pStart = findTerm(&wc, iCur, -1, notReady, WO_GT|WO_GE, 0);
+ pEnd = findTerm(&wc, iCur, -1, notReady, WO_LT|WO_LE, 0);
+ if( bRev ){
+ pTerm = pStart;
+ pStart = pEnd;
+ pEnd = pTerm;
+ }
+ if( pStart ){
+ Expr *pX;
+ int r1, regFree1;
+ pX = pStart->pExpr;
+ assert( pX!=0 );
+ assert( pStart->leftCursor==iCur );
+ r1 = sqlite3ExprCodeTemp(pParse, pX->pRight, ®Free1);
+ sqlite3VdbeAddOp3(v, OP_ForceInt, r1, brk,
+ pX->op==TK_LE || pX->op==TK_GT);
+ sqlite3VdbeAddOp3(v, bRev ? OP_MoveLt : OP_MoveGe, iCur, brk, r1);
+ VdbeComment((v, "pk"));
+ sqlite3ReleaseTempReg(pParse, regFree1);
+ disableTerm(pLevel, pStart);
+ }else{
+ sqlite3VdbeAddOp2(v, bRev ? OP_Last : OP_Rewind, iCur, brk);
+ }
+ if( pEnd ){
+ Expr *pX;
+ pX = pEnd->pExpr;
+ assert( pX!=0 );
+ assert( pEnd->leftCursor==iCur );
+ pLevel->iMem = ++pParse->nMem;
+ sqlite3ExprCode(pParse, pX->pRight, pLevel->iMem);
+ if( pX->op==TK_LT || pX->op==TK_GT ){
+ testOp = bRev ? OP_Le : OP_Ge;
+ }else{
+ testOp = bRev ? OP_Lt : OP_Gt;
+ }
+ disableTerm(pLevel, pEnd);
+ }
+ start = sqlite3VdbeCurrentAddr(v);
+ pLevel->op = bRev ? OP_Prev : OP_Next;
+ pLevel->p1 = iCur;
+ pLevel->p2 = start;
+ if( testOp!=OP_Noop ){
+ int r1 = sqlite3GetTempReg(pParse);
+ sqlite3VdbeAddOp2(v, OP_Rowid, iCur, r1);
+ /* sqlite3VdbeAddOp2(v, OP_SCopy, pLevel->iMem, 0); */
+ sqlite3VdbeAddOp3(v, testOp, pLevel->iMem, brk, r1);
+ sqlite3VdbeChangeP5(v, SQLITE_AFF_NUMERIC | SQLITE_JUMPIFNULL);
+ sqlite3ReleaseTempReg(pParse, r1);
+ }
+ }else if( pLevel->flags & (WHERE_COLUMN_RANGE|WHERE_COLUMN_EQ) ){
+ /* Case 3: A scan using an index.
+ **
+ ** The WHERE clause may contain zero or more equality
+ ** terms ("==" or "IN" operators) that refer to the N
+ ** left-most columns of the index. It may also contain
+ ** inequality constraints (>, <, >= or <=) on the indexed
+ ** column that immediately follows the N equalities. Only
+ ** the right-most column can be an inequality - the rest must
+ ** use the "==" and "IN" operators. For example, if the
+ ** index is on (x,y,z), then the following clauses are all
+ ** optimized:
+ **
+ ** x=5
+ ** x=5 AND y=10
+ ** x=5 AND y<10
+ ** x=5 AND y>5 AND y<10
+ ** x=5 AND y=5 AND z<=10
+ **
+ ** The z<10 term of the following cannot be used, only
+ ** the x=5 term:
+ **
+ ** x=5 AND z<10
+ **
+ ** N may be zero if there are inequality constraints.
+ ** If there are no inequality constraints, then N is at
+ ** least one.
+ **
+ ** This case is also used when there are no WHERE clause
+ ** constraints but an index is selected anyway, in order
+ ** to force the output order to conform to an ORDER BY.
+ */
+ int aStartOp[] = {
+ 0,
+ 0,
+ OP_Rewind, /* 2: (!start_constraints && startEq && !bRev) */
+ OP_Last, /* 3: (!start_constraints && startEq && bRev) */
+ OP_MoveGt, /* 4: (start_constraints && !startEq && !bRev) */
+ OP_MoveLt, /* 5: (start_constraints && !startEq && bRev) */
+ OP_MoveGe, /* 6: (start_constraints && startEq && !bRev) */
+ OP_MoveLe /* 7: (start_constraints && startEq && bRev) */
+ };
+ int aEndOp[] = {
+ OP_Noop, /* 0: (!end_constraints) */
+ OP_IdxGE, /* 1: (end_constraints && !bRev) */
+ OP_IdxLT /* 2: (end_constraints && bRev) */
+ };
+ int nEq = pLevel->nEq;
+ int isMinQuery = 0; /* If this is an optimized SELECT min(x).. */
+ int regBase; /* Base register holding constraint values */
+ int r1; /* Temp register */
+ WhereTerm *pRangeStart = 0; /* Inequality constraint at range start */
+ WhereTerm *pRangeEnd = 0; /* Inequality constraint at range end */
+ int startEq; /* True if range start uses ==, >= or <= */
+ int endEq; /* True if range end uses ==, >= or <= */
+ int start_constraints; /* Start of range is constrained */
+ int k = pIdx->aiColumn[nEq]; /* Column for inequality constraints */
+ int nConstraint; /* Number of constraint terms */
+ int op;
+
+ /* Generate code to evaluate all constraint terms using == or IN
+ ** and store the values of those terms in an array of registers
+ ** starting at regBase.
+ */
+ regBase = codeAllEqualityTerms(pParse, pLevel, &wc, notReady, 2);
+ nxt = pLevel->nxt;
+
+ /* If this loop satisfies a sort order (pOrderBy) request that
+ ** was passed to this function to implement a "SELECT min(x) ..."
+ ** query, then the caller will only allow the loop to run for
+ ** a single iteration. This means that the first row returned
+ ** should not have a NULL value stored in 'x'. If column 'x' is
+ ** the first one after the nEq equality constraints in the index,
+ ** this requires some special handling.
+ */
+ if( (wflags&WHERE_ORDERBY_MIN)!=0
+ && (pLevel->flags&WHERE_ORDERBY)
+ && (pIdx->nColumn>nEq)
+ ){
+ assert( pOrderBy->nExpr==1 );
+ assert( pOrderBy->a[0].pExpr->iColumn==pIdx->aiColumn[nEq] );
+ isMinQuery = 1;
+ }
+
+ /* Find any inequality constraint terms for the start and end
+ ** of the range.
+ */
+ if( pLevel->flags & WHERE_TOP_LIMIT ){
+ pRangeEnd = findTerm(&wc, iCur, k, notReady, (WO_LT|WO_LE), pIdx);
+ }
+ if( pLevel->flags & WHERE_BTM_LIMIT ){
+ pRangeStart = findTerm(&wc, iCur, k, notReady, (WO_GT|WO_GE), pIdx);
+ }
+
+ /* If we are doing a reverse order scan on an ascending index, or
+ ** a forward order scan on a descending index, interchange the
+ ** start and end terms (pRangeStart and pRangeEnd).
+ */
+ if( bRev==(pIdx->aSortOrder[nEq]==SQLITE_SO_ASC) ){
+ SWAP(WhereTerm *, pRangeEnd, pRangeStart);
+ }
+
+ testcase( pRangeStart && pRangeStart->eOperator & WO_LE );
+ testcase( pRangeStart && pRangeStart->eOperator & WO_GE );
+ testcase( pRangeEnd && pRangeEnd->eOperator & WO_LE );
+ testcase( pRangeEnd && pRangeEnd->eOperator & WO_GE );
+ startEq = !pRangeStart || pRangeStart->eOperator & (WO_LE|WO_GE);
+ endEq = !pRangeEnd || pRangeEnd->eOperator & (WO_LE|WO_GE);
+ start_constraints = pRangeStart || nEq>0;
+
+ /* Seek the index cursor to the start of the range. */
+ nConstraint = nEq;
+ if( pRangeStart ){
+ int dcc = pParse->disableColCache;
+ if( pRangeEnd ){
+ pParse->disableColCache++;
+ }
+ sqlite3ExprCode(pParse, pRangeStart->pExpr->pRight, regBase+nEq);
+ pParse->disableColCache = dcc;
+ sqlite3VdbeAddOp2(v, OP_IsNull, regBase+nEq, nxt);
+ nConstraint++;
+ }else if( isMinQuery ){
+ sqlite3VdbeAddOp2(v, OP_Null, 0, regBase+nEq);
+ nConstraint++;
+ startEq = 0;
+ start_constraints = 1;
+ }
+ codeApplyAffinity(pParse, regBase, nConstraint, pIdx);
+ op = aStartOp[(start_constraints<<2) + (startEq<<1) + bRev];
+ assert( op!=0 );
+ testcase( op==OP_Rewind );
+ testcase( op==OP_Last );
+ testcase( op==OP_MoveGt );
+ testcase( op==OP_MoveGe );
+ testcase( op==OP_MoveLe );
+ testcase( op==OP_MoveLt );
+ sqlite3VdbeAddOp4(v, op, iIdxCur, nxt, regBase,
+ SQLITE_INT_TO_PTR(nConstraint), P4_INT32);
+
+ /* Load the value for the inequality constraint at the end of the
+ ** range (if any).
+ */
+ nConstraint = nEq;
+ if( pRangeEnd ){
+ sqlite3ExprCode(pParse, pRangeEnd->pExpr->pRight, regBase+nEq);
+ sqlite3VdbeAddOp2(v, OP_IsNull, regBase+nEq, nxt);
+ codeApplyAffinity(pParse, regBase, nEq+1, pIdx);
+ nConstraint++;
+ }
+
+ /* Top of the loop body */
+ pLevel->p2 = sqlite3VdbeCurrentAddr(v);
+
+ /* Check if the index cursor is past the end of the range. */
+ op = aEndOp[(pRangeEnd || nEq) * (1 + bRev)];
+ testcase( op==OP_Noop );
+ testcase( op==OP_IdxGE );
+ testcase( op==OP_IdxLT );
+ sqlite3VdbeAddOp4(v, op, iIdxCur, nxt, regBase,
+ SQLITE_INT_TO_PTR(nConstraint), P4_INT32);
+ sqlite3VdbeChangeP5(v, endEq!=bRev);
+
+ /* If there are inequality constraints, check that the value
+ ** of the table column that the inequality contrains is not NULL.
+ ** If it is, jump to the next iteration of the loop.
+ */
+ r1 = sqlite3GetTempReg(pParse);
+ testcase( pLevel->flags & WHERE_BTM_LIMIT );
+ testcase( pLevel->flags & WHERE_TOP_LIMIT );
+ if( pLevel->flags & (WHERE_BTM_LIMIT|WHERE_TOP_LIMIT) ){
+ sqlite3VdbeAddOp3(v, OP_Column, iIdxCur, nEq, r1);
+ sqlite3VdbeAddOp2(v, OP_IsNull, r1, cont);
+ }
+
+ /* Seek the table cursor, if required */
+ if( !omitTable ){
+ sqlite3VdbeAddOp2(v, OP_IdxRowid, iIdxCur, r1);
+ sqlite3VdbeAddOp3(v, OP_MoveGe, iCur, 0, r1); /* Deferred seek */
+ }
+ sqlite3ReleaseTempReg(pParse, r1);
+
+ /* Record the instruction used to terminate the loop. Disable
+ ** WHERE clause terms made redundant by the index range scan.
+ */
+ pLevel->op = bRev ? OP_Prev : OP_Next;
+ pLevel->p1 = iIdxCur;
+ disableTerm(pLevel, pRangeStart);
+ disableTerm(pLevel, pRangeEnd);
+ }else{
+ /* Case 4: There is no usable index. We must do a complete
+ ** scan of the entire table.
+ */
+ assert( omitTable==0 );
+ assert( bRev==0 );
+ pLevel->op = OP_Next;
+ pLevel->p1 = iCur;
+ pLevel->p2 = 1 + sqlite3VdbeAddOp2(v, OP_Rewind, iCur, brk);
+ }
+ notReady &= ~getMask(&maskSet, iCur);
+
+ /* Insert code to test every subexpression that can be completely
+ ** computed using the current set of tables.
+ */
+ for(pTerm=wc.a, j=wc.nTerm; j>0; j--, pTerm++){
+ Expr *pE;
+ testcase( pTerm->flags & TERM_VIRTUAL );
+ testcase( pTerm->flags & TERM_CODED );
+ if( pTerm->flags & (TERM_VIRTUAL|TERM_CODED) ) continue;
+ if( (pTerm->prereqAll & notReady)!=0 ) continue;
+ pE = pTerm->pExpr;
+ assert( pE!=0 );
+ if( pLevel->iLeftJoin && !ExprHasProperty(pE, EP_FromJoin) ){
+ continue;
+ }
+ sqlite3ExprIfFalse(pParse, pE, cont, SQLITE_JUMPIFNULL);
+ pTerm->flags |= TERM_CODED;
+ }
+
+ /* For a LEFT OUTER JOIN, generate code that will record the fact that
+ ** at least one row of the right table has matched the left table.
+ */
+ if( pLevel->iLeftJoin ){
+ pLevel->top = sqlite3VdbeCurrentAddr(v);
+ sqlite3VdbeAddOp2(v, OP_Integer, 1, pLevel->iLeftJoin);
+ VdbeComment((v, "record LEFT JOIN hit"));
+ sqlite3ExprClearColumnCache(pParse, pLevel->iTabCur);
+ sqlite3ExprClearColumnCache(pParse, pLevel->iIdxCur);
+ for(pTerm=wc.a, j=0; j<wc.nTerm; j++, pTerm++){
+ testcase( pTerm->flags & TERM_VIRTUAL );
+ testcase( pTerm->flags & TERM_CODED );
+ if( pTerm->flags & (TERM_VIRTUAL|TERM_CODED) ) continue;
+ if( (pTerm->prereqAll & notReady)!=0 ) continue;
+ assert( pTerm->pExpr );
+ sqlite3ExprIfFalse(pParse, pTerm->pExpr, cont, SQLITE_JUMPIFNULL);
+ pTerm->flags |= TERM_CODED;
+ }
+ }
+ }
+
+#ifdef SQLITE_TEST /* For testing and debugging use only */
+ /* Record in the query plan information about the current table
+ ** and the index used to access it (if any). If the table itself
+ ** is not used, its name is just '{}'. If no index is used
+ ** the index is listed as "{}". If the primary key is used the
+ ** index name is '*'.
+ */
+ for(i=0; i<pTabList->nSrc; i++){
+ char *z;
+ int n;
+ pLevel = &pWInfo->a[i];
+ pTabItem = &pTabList->a[pLevel->iFrom];
+ z = pTabItem->zAlias;
+ if( z==0 ) z = pTabItem->pTab->zName;
+ n = strlen(z);
+ if( n+nQPlan < sizeof(sqlite3_query_plan)-10 ){
+ if( pLevel->flags & WHERE_IDX_ONLY ){
+ memcpy(&sqlite3_query_plan[nQPlan], "{}", 2);
+ nQPlan += 2;
+ }else{
+ memcpy(&sqlite3_query_plan[nQPlan], z, n);
+ nQPlan += n;
+ }
+ sqlite3_query_plan[nQPlan++] = ' ';
+ }
+ testcase( pLevel->flags & WHERE_ROWID_EQ );
+ testcase( pLevel->flags & WHERE_ROWID_RANGE );
+ if( pLevel->flags & (WHERE_ROWID_EQ|WHERE_ROWID_RANGE) ){
+ memcpy(&sqlite3_query_plan[nQPlan], "* ", 2);
+ nQPlan += 2;
+ }else if( pLevel->pIdx==0 ){
+ memcpy(&sqlite3_query_plan[nQPlan], "{} ", 3);
+ nQPlan += 3;
+ }else{
+ n = strlen(pLevel->pIdx->zName);
+ if( n+nQPlan < sizeof(sqlite3_query_plan)-2 ){
+ memcpy(&sqlite3_query_plan[nQPlan], pLevel->pIdx->zName, n);
+ nQPlan += n;
+ sqlite3_query_plan[nQPlan++] = ' ';
+ }
+ }
+ }
+ while( nQPlan>0 && sqlite3_query_plan[nQPlan-1]==' ' ){
+ sqlite3_query_plan[--nQPlan] = 0;
+ }
+ sqlite3_query_plan[nQPlan] = 0;
+ nQPlan = 0;
+#endif /* SQLITE_TEST // Testing and debugging use only */
+
+ /* Record the continuation address in the WhereInfo structure. Then
+ ** clean up and return.
+ */
+ pWInfo->iContinue = cont;
+ whereClauseClear(&wc);
+ return pWInfo;
+
+ /* Jump here if malloc fails */
+whereBeginNoMem:
+ whereClauseClear(&wc);
+ whereInfoFree(pWInfo);
+ return 0;
+}
+
+/*
+** Generate the end of the WHERE loop. See comments on
+** sqlite3WhereBegin() for additional information.
+*/
+void sqlite3WhereEnd(WhereInfo *pWInfo){
+ Parse *pParse = pWInfo->pParse;
+ Vdbe *v = pParse->pVdbe;
+ int i;
+ WhereLevel *pLevel;
+ SrcList *pTabList = pWInfo->pTabList;
+ sqlite3 *db = pParse->db;
+
+ /* Generate loop termination code.
+ */
+ sqlite3ExprClearColumnCache(pParse, -1);
+ for(i=pTabList->nSrc-1; i>=0; i--){
+ pLevel = &pWInfo->a[i];
+ sqlite3VdbeResolveLabel(v, pLevel->cont);
+ if( pLevel->op!=OP_Noop ){
+ sqlite3VdbeAddOp2(v, pLevel->op, pLevel->p1, pLevel->p2);
+ }
+ if( pLevel->nIn ){
+ struct InLoop *pIn;
+ int j;
+ sqlite3VdbeResolveLabel(v, pLevel->nxt);
+ for(j=pLevel->nIn, pIn=&pLevel->aInLoop[j-1]; j>0; j--, pIn--){
+ sqlite3VdbeJumpHere(v, pIn->topAddr+1);
+ sqlite3VdbeAddOp2(v, OP_Next, pIn->iCur, pIn->topAddr);
+ sqlite3VdbeJumpHere(v, pIn->topAddr-1);
+ }
+ sqlite3DbFree(db, pLevel->aInLoop);
+ }
+ sqlite3VdbeResolveLabel(v, pLevel->brk);
+ if( pLevel->iLeftJoin ){
+ int addr;
+ addr = sqlite3VdbeAddOp1(v, OP_IfPos, pLevel->iLeftJoin);
+ sqlite3VdbeAddOp1(v, OP_NullRow, pTabList->a[i].iCursor);
+ if( pLevel->iIdxCur>=0 ){
+ sqlite3VdbeAddOp1(v, OP_NullRow, pLevel->iIdxCur);
+ }
+ sqlite3VdbeAddOp2(v, OP_Goto, 0, pLevel->top);
+ sqlite3VdbeJumpHere(v, addr);
+ }
+ }
+
+ /* The "break" point is here, just past the end of the outer loop.
+ ** Set it.
+ */
+ sqlite3VdbeResolveLabel(v, pWInfo->iBreak);
+
+ /* Close all of the cursors that were opened by sqlite3WhereBegin.
+ */
+ for(i=0, pLevel=pWInfo->a; i<pTabList->nSrc; i++, pLevel++){
+ struct SrcList_item *pTabItem = &pTabList->a[pLevel->iFrom];
+ Table *pTab = pTabItem->pTab;
+ assert( pTab!=0 );
+ if( pTab->isEphem || pTab->pSelect ) continue;
+ if( !pWInfo->okOnePass && (pLevel->flags & WHERE_IDX_ONLY)==0 ){
+ sqlite3VdbeAddOp1(v, OP_Close, pTabItem->iCursor);
+ }
+ if( pLevel->pIdx!=0 ){
+ sqlite3VdbeAddOp1(v, OP_Close, pLevel->iIdxCur);
+ }
+
+ /* If this scan uses an index, make code substitutions to read data
+ ** from the index in preference to the table. Sometimes, this means
+ ** the table need never be read from. This is a performance boost,
+ ** as the vdbe level waits until the table is read before actually
+ ** seeking the table cursor to the record corresponding to the current
+ ** position in the index.
+ **
+ ** Calls to the code generator in between sqlite3WhereBegin and
+ ** sqlite3WhereEnd will have created code that references the table
+ ** directly. This loop scans all that code looking for opcodes
+ ** that reference the table and converts them into opcodes that
+ ** reference the index.
+ */
+ if( pLevel->pIdx ){
+ int k, j, last;
+ VdbeOp *pOp;
+ Index *pIdx = pLevel->pIdx;
+ int useIndexOnly = pLevel->flags & WHERE_IDX_ONLY;
+
+ assert( pIdx!=0 );
+ pOp = sqlite3VdbeGetOp(v, pWInfo->iTop);
+ last = sqlite3VdbeCurrentAddr(v);
+ for(k=pWInfo->iTop; k<last; k++, pOp++){
+ if( pOp->p1!=pLevel->iTabCur ) continue;
+ if( pOp->opcode==OP_Column ){
+ for(j=0; j<pIdx->nColumn; j++){
+ if( pOp->p2==pIdx->aiColumn[j] ){
+ pOp->p2 = j;
+ pOp->p1 = pLevel->iIdxCur;
+ break;
+ }
+ }
+ assert(!useIndexOnly || j<pIdx->nColumn);
+ }else if( pOp->opcode==OP_Rowid ){
+ pOp->p1 = pLevel->iIdxCur;
+ pOp->opcode = OP_IdxRowid;
+ }else if( pOp->opcode==OP_NullRow && useIndexOnly ){
+ pOp->opcode = OP_Noop;
+ }
+ }
+ }
+ }
+
+ /* Final cleanup
+ */
+ whereInfoFree(pWInfo);
+ return;
+}