--- a/engine/sqlite/src/where.cpp Wed Apr 28 13:20:05 2010 +0100
+++ /dev/null Thu Jan 01 00:00:00 1970 +0000
@@ -1,2789 +0,0 @@
-/*
-** 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 reponsible 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.cpp 1282 2008-11-13 09:31:33Z LarsPson $
-*/
-#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 sqlite3_where_trace = 0;
-# define WHERETRACE(X) if(sqlite3_where_trace) 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(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;
- for(i=pWC->nTerm-1, a=pWC->a; i>=0; i--, a++){
- if( a->flags & TERM_DYNAMIC ){
- sqlite3ExprDelete(a->pExpr);
- }
- }
- if( pWC->a!=pWC->aStatic ){
- sqlite3_free(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 invalided 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;
- pWC->a = (WhereTerm*)sqlite3_malloc( sizeof(pWC->a[0])*pWC->nSlot*2 );
- if( pWC->a==0 ){
- pWC->pParse->db->mallocFailed = 1;
- if( flags & TERM_DYNAMIC ){
- sqlite3ExprDelete(p);
- }
- pWC->a = pOld;
- return 0;
- }
- memcpy(pWC->a, pOld, sizeof(pWC->a[0])*pWC->nTerm);
- if( pOld!=pWC->aStatic ){
- sqlite3_free(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 comparision 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;
- 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( iCur>=0 && 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; j<pIdx->nColumn && pIdx->aiColumn[j]!=iColumn; j++){}
- assert( j<pIdx->nColumn );
- 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 */
-){
- const char *z;
- Expr *pRight, *pLeft;
- ExprList *pList;
- int c, cnt;
- int noCase;
- char wc[3];
- CollSeq *pColl;
-
- if( !sqlite3IsLikeFunction(db, pExpr, &noCase, wc) ){
- return 0;
- }
- pList = pExpr->pList;
- pRight = pList->a[0].pExpr;
- if( pRight->op!=TK_STRING ){
- return 0;
- }
- pLeft = pList->a[1].pExpr;
- if( pLeft->op!=TK_COLUMN ){
- return 0;
- }
- pColl = pLeft->pColl;
- if( pColl==0 ){
- /* TODO: Coverage testing doesn't get this case. Is it actually possible
- ** for an expression of type TK_COLUMN to not have an assigned collation
- ** sequence at this point?
- */
- pColl = db->pDfltColl;
- }
- if( (pColl->type!=SQLITE_COLL_BINARY || noCase) &&
- (pColl->type!=SQLITE_COLL_NOCASE || !noCase) ){
- 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 condidate 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 disqualifed, 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;
- int nPattern;
- int isComplete;
- 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) ){
- prereqAll |= getMask(pMaskSet, pExpr->iRightJoinTable);
- }
- 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(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;
- 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 && ok; 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(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.
- */
- if( isLikeOrGlob(db, pExpr, &nPattern, &isComplete) ){
- 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 ){
- assert( pStr2->token.dyn );
- ++*(u8*)&pStr2->token.z[nPattern-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 */
-}
-
-/*
-** 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 */
- ExprList::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 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 operatings 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( !sqlite3_where_trace ) 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( !sqlite3_where_trace ) 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 */
- SrcList::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_index_info *pIdxInfo;
- sqlite3_index_info::sqlite3_index_constraint *pIdxCons;
- sqlite3_index_info::sqlite3_index_orderby *pIdxOrderBy;
- sqlite3_index_info::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==WO_IN ) continue;
- if( pTerm->eOperator==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 = (sqlite3_index_info*)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 = (sqlite3_index_info::sqlite3_index_constraint*)&pIdxInfo[1];
- pIdxOrderBy = (sqlite3_index_info::sqlite3_index_orderby*)&pIdxCons[nTerm];
- pUsage = (sqlite3_index_info::sqlite3_index_constraint_usage*)&pIdxOrderBy[nOrderBy];
- *(int*)&pIdxInfo->nConstraint = nTerm;
- *(int*)&pIdxInfo->nOrderBy = nOrderBy;
- *(sqlite3_index_info::sqlite3_index_constraint**)&pIdxInfo->aConstraint = pIdxCons;
- *(sqlite3_index_info::sqlite3_index_orderby**)&pIdxInfo->aOrderBy = pIdxOrderBy;
- *(sqlite3_index_info::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==WO_IN ) continue;
- if( pTerm->eOperator==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( pTab->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 = *(sqlite3_index_info::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;
- }
-
- sqlite3SafetyOff(pParse->db);
- WHERETRACE(("xBestIndex for %s\n", pTab->zName));
- TRACE_IDX_INPUTS(pIdxInfo);
- rc = pTab->pVtab->pModule->xBestIndex(pTab->pVtab, pIdxInfo);
- TRACE_IDX_OUTPUTS(pIdxInfo);
- if( rc!=SQLITE_OK ){
- if( rc==SQLITE_NOMEM ){
- pParse->db->mallocFailed = 1;
- }else {
- sqlite3ErrorMsg(pParse, "%s", sqlite3ErrStr(rc));
- }
- sqlite3SafetyOn(pParse->db);
- }else{
- rc = sqlite3SafetyOn(pParse->db);
- }
- *(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 */
- SrcList::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=%x\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( pExpr->pList!=0 ){
- 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
- && (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);
- }
- }
- }
-}
-
-/*
-** Generate code that builds a probe for an index.
-**
-** There should be nColumn values on the stack. The index
-** to be probed is pIdx. Pop the values from the stack and
-** replace them all with a single record that is the index
-** problem.
-*/
-static void buildIndexProbe(
- Vdbe *v, /* Generate code into this VM */
- int nColumn, /* The number of columns to check for NULL */
- Index *pIdx /* Index that we will be searching */
-){
- sqlite3VdbeAddOp(v, OP_MakeRecord, nColumn, 0);
- sqlite3IndexAffinityStr(v, pIdx);
-}
-
-
-/*
-** 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 on the top of the stack.
-**
-** 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 void 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 */
-){
- Expr *pX = pTerm->pExpr;
- Vdbe *v = pParse->pVdbe;
- if( pX->op==TK_EQ ){
- sqlite3ExprCode(pParse, pX->pRight);
- }else if( pX->op==TK_ISNULL ){
- sqlite3VdbeAddOp(v, OP_Null, 0, 0);
-#ifndef SQLITE_OMIT_SUBQUERY
- }else{
- int eType;
- int iTab;
- WhereLevel::InLoop *pIn;
-
- assert( pX->op==TK_IN );
- eType = sqlite3FindInIndex(pParse, pX, 1);
- iTab = pX->iTable;
- sqlite3VdbeAddOp(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 = (WhereLevel::InLoop*)sqlite3DbReallocOrFree(pParse->db, pLevel->aInLoop,
- sizeof(pLevel->aInLoop[0])*pLevel->nIn);
- pIn = (WhereLevel::InLoop*)pLevel->aInLoop;
- if( pIn ){
- int op = ((eType==IN_INDEX_ROWID)?OP_Rowid:OP_Column);
- pIn += pLevel->nIn - 1;
- pIn->iCur = iTab;
- pIn->topAddr = sqlite3VdbeAddOp(v, op, iTab, 0);
- sqlite3VdbeAddOp(v, OP_IsNull, -1, 0);
- }else{
- pLevel->nIn = 0;
- }
-#endif
- }
- disableTerm(pLevel, pTerm);
-}
-
-/*
-** 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 void 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 nEq = pLevel->nEq; /* The number of == or IN constraints to code */
- int termsInMem = 0; /* If true, store value in mem[] cells */
- 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 */
-
- /* 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++;
- if( pLevel->flags & WHERE_COLUMN_IN ){
- pParse->nMem += pLevel->nEq;
- termsInMem = 1;
- }
-
- /* Evaluate the equality constraints
- */
- assert( pIdx->nColumn>=nEq );
- for(j=0; j<nEq; j++){
- int k = pIdx->aiColumn[j];
- pTerm = findTerm(pWC, iCur, k, notReady, pLevel->flags, pIdx);
- if( pTerm==0 ) break;
- assert( (pTerm->flags & TERM_CODED)==0 );
- codeEqualityTerm(pParse, pTerm, pLevel);
- if( (pTerm->eOperator & (WO_ISNULL|WO_IN))==0 ){
- sqlite3VdbeAddOp(v, OP_IsNull, termsInMem ? -1 : -(j+1), pLevel->brk);
- }
- if( termsInMem ){
- sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem+j+1, 1);
- }
- }
-
- /* Make sure all the constraint values are on the top of the stack
- */
- if( termsInMem ){
- for(j=0; j<nEq; j++){
- sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem+j+1, 0);
- }
- }
-}
-
-#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;
- for(i=0; i<pWInfo->nLevel; i++){
- sqlite3_index_info *pInfo = pWInfo->a[i].pIdxInfo;
- if( pInfo ){
- if( pInfo->needToFreeIdxStr ){
- /* Coverage: Don't think this can be reached. By the time this
- ** function is called, the index-strings have been passed
- ** to the vdbe layer for deletion.
- */
- sqlite3_free(pInfo->idxStr);
- }
- sqlite3_free(pInfo);
- }
- }
- sqlite3_free(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 */
-){
- 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 */
- SrcList::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 */
-
- /* 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;
- }
-
- /* Split the WHERE clause into separate subexpressions where each
- ** subexpression is separated by an AND operator.
- */
- initMaskSet(&maskSet);
- whereClauseInit(&wc, pParse, &maskSet);
- whereSplit(&wc, pWhere, TK_AND);
-
- /* Allocate and initialize the WhereInfo structure that will become the
- ** return value.
- */
- db = pParse->db;
- pWInfo = (WhereInfo*)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, 1);
- pWhere = 0;
- }
-
- /* 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.
- */
- for(i=0; i<pTabList->nSrc; i++){
- createMask(&maskSet, pTabList->a[i].iCursor);
- }
- 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 choose 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;
- }
-
- /* 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;
- SrcList::SrcList_item *pItem = &pTabList->a[pLevel->iFrom];
- zMsg = sqlite3MPrintf(db, "TABLE %s", pItem->zName);
- if( pItem->zAlias ){
- zMsg = sqlite3MPrintf(db, "%z AS %s", zMsg, pItem->zAlias);
- }
- if( (pIx = pLevel->pIdx)!=0 ){
- zMsg = sqlite3MPrintf(db, "%z WITH INDEX %s", zMsg, pIx->zName);
- }else if( pLevel->flags & (WHERE_ROWID_EQ|WHERE_ROWID_RANGE) ){
- zMsg = sqlite3MPrintf(db, "%z USING PRIMARY KEY", zMsg);
- }
-#ifndef SQLITE_OMIT_VIRTUALTABLE
- else if( pLevel->pBestIdx ){
- sqlite3_index_info *pBestIdx = pLevel->pBestIdx;
- zMsg = sqlite3MPrintf(db, "%z VIRTUAL TABLE INDEX %d:%s", zMsg,
- pBestIdx->idxNum, pBestIdx->idxStr);
- }
-#endif
- if( pLevel->flags & WHERE_ORDERBY ){
- zMsg = sqlite3MPrintf(db, "%z ORDER BY", zMsg);
- }
- sqlite3VdbeOp3(v, OP_Explain, i, pLevel->iFrom, zMsg, P3_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;
- sqlite3VdbeOp3(v, OP_VOpen, iCur, 0, (const char*)pTab->pVtab, P3_VTAB);
- }else
-#endif
- if( (pLevel->flags & WHERE_IDX_ONLY)==0 ){
- sqlite3OpenTable(pParse, pTabItem->iCursor, iDb, pTab, OP_OpenRead);
- if( pTab->nCol<(sizeof(Bitmask)*8) ){
- Bitmask b = pTabItem->colUsed;
- int n = 0;
- for(; b; b=b>>1, n++){}
- sqlite3VdbeChangeP2(v, sqlite3VdbeCurrentAddr(v)-1, 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 );
- sqlite3VdbeAddOp(v, OP_Integer, iDb, 0);
- VdbeComment((v, "# %s", pIx->zName));
- sqlite3VdbeOp3(v, OP_OpenRead, iIdxCur, pIx->tnum,
- (char*)pKey, P3_KEYINFO_HANDOFF);
- sqlite3VdbeAddOp(v, OP_SetNumColumns, iIdxCur, pIx->nColumn+1);
- }
- 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 ){
- if( !pParse->nMem ) pParse->nMem++;
- pLevel->iLeftJoin = pParse->nMem++;
- sqlite3VdbeAddOp(v, OP_MemInt, 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;
- sqlite3_index_info *pBestIdx = pLevel->pBestIdx;
- int nConstraint = pBestIdx->nConstraint;
- sqlite3_index_info::sqlite3_index_constraint_usage *aUsage =
- pBestIdx->aConstraintUsage;
- const sqlite3_index_info::sqlite3_index_constraint *aConstraint =
- pBestIdx->aConstraint;
-
- for(j=1; j<=nConstraint; j++){
- int k;
- for(k=0; k<nConstraint; k++){
- if( aUsage[k].argvIndex==j ){
- int iTerm = aConstraint[k].iTermOffset;
- sqlite3ExprCode(pParse, wc.a[iTerm].pExpr->pRight);
- break;
- }
- }
- if( k==nConstraint ) break;
- }
- sqlite3VdbeAddOp(v, OP_Integer, j-1, 0);
- sqlite3VdbeAddOp(v, OP_Integer, pBestIdx->idxNum, 0);
- sqlite3VdbeOp3(v, OP_VFilter, iCur, brk, pBestIdx->idxStr,
- pBestIdx->needToFreeIdxStr ? P3_MPRINTF : P3_STATIC);
- pBestIdx->needToFreeIdxStr = 0;
- for(j=0; j<pBestIdx->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.
- */
- 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 );
- codeEqualityTerm(pParse, pTerm, pLevel);
- nxt = pLevel->nxt;
- sqlite3VdbeAddOp(v, OP_MustBeInt, 1, nxt);
- sqlite3VdbeAddOp(v, OP_NotExists, iCur, nxt);
- 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;
- pX = pStart->pExpr;
- assert( pX!=0 );
- assert( pStart->leftCursor==iCur );
- sqlite3ExprCode(pParse, pX->pRight);
- sqlite3VdbeAddOp(v, OP_ForceInt, pX->op==TK_LE || pX->op==TK_GT, brk);
- sqlite3VdbeAddOp(v, bRev ? OP_MoveLt : OP_MoveGe, iCur, brk);
- VdbeComment((v, "pk"));
- disableTerm(pLevel, pStart);
- }else{
- sqlite3VdbeAddOp(v, bRev ? OP_Last : OP_Rewind, iCur, brk);
- }
- if( pEnd ){
- Expr *pX;
- pX = pEnd->pExpr;
- assert( pX!=0 );
- assert( pEnd->leftCursor==iCur );
- sqlite3ExprCode(pParse, pX->pRight);
- pLevel->iMem = pParse->nMem++;
- sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 1);
- 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 ){
- sqlite3VdbeAddOp(v, OP_Rowid, iCur, 0);
- sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0);
- sqlite3VdbeAddOp(v, testOp, SQLITE_AFF_NUMERIC|0x100, brk);
- }
- }else if( pLevel->flags & WHERE_COLUMN_RANGE ){
- /* Case 3: The WHERE clause term that refers to the right-most
- ** column of the index is an inequality. For example, if
- ** the index is on (x,y,z) and the WHERE clause is of the
- ** form "x=5 AND y<10" then this case is used. Only the
- ** right-most column can be an inequality - the rest must
- ** use the "==" and "IN" operators.
- **
- ** 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 start;
- int nEq = pLevel->nEq;
- int topEq=0; /* True if top limit uses ==. False is strictly < */
- int btmEq=0; /* True if btm limit uses ==. False if strictly > */
- int topOp, btmOp; /* Operators for the top and bottom search bounds */
- int testOp;
- int topLimit = (pLevel->flags & WHERE_TOP_LIMIT)!=0;
- int btmLimit = (pLevel->flags & WHERE_BTM_LIMIT)!=0;
-
- /* Generate code to evaluate all constraint terms using == or IN
- ** and level the values of those terms on the stack.
- */
- codeAllEqualityTerms(pParse, pLevel, &wc, notReady);
-
- /* Duplicate the equality term values because they will all be
- ** used twice: once to make the termination key and once to make the
- ** start key.
- */
- for(j=0; j<nEq; j++){
- sqlite3VdbeAddOp(v, OP_Dup, nEq-1, 0);
- }
-
- /* Figure out what comparison operators to use for top and bottom
- ** search bounds. For an ascending index, the bottom bound is a > or >=
- ** operator and the top bound is a < or <= operator. For a descending
- ** index the operators are reversed.
- */
- if( pIdx->aSortOrder[nEq]==SQLITE_SO_ASC ){
- topOp = WO_LT|WO_LE;
- btmOp = WO_GT|WO_GE;
- }else{
- topOp = WO_GT|WO_GE;
- btmOp = WO_LT|WO_LE;
- SWAP(int, topLimit, btmLimit);
- }
-
- /* Generate the termination key. This is the key value that
- ** will end the search. There is no termination key if there
- ** are no equality terms and no "X<..." term.
- **
- ** 2002-Dec-04: On a reverse-order scan, the so-called "termination"
- ** key computed here really ends up being the start key.
- */
- nxt = pLevel->nxt;
- if( topLimit ){
- Expr *pX;
- int k = pIdx->aiColumn[j];
- pTerm = findTerm(&wc, iCur, k, notReady, topOp, pIdx);
- assert( pTerm!=0 );
- pX = pTerm->pExpr;
- assert( (pTerm->flags & TERM_CODED)==0 );
- sqlite3ExprCode(pParse, pX->pRight);
- sqlite3VdbeAddOp(v, OP_IsNull, -(nEq*2+1), nxt);
- topEq = pTerm->eOperator & (WO_LE|WO_GE);
- disableTerm(pLevel, pTerm);
- testOp = OP_IdxGE;
- }else{
- testOp = nEq>0 ? OP_IdxGE : OP_Noop;
- topEq = 1;
- }
- if( testOp!=OP_Noop ){
- int nCol = nEq + topLimit;
- pLevel->iMem = pParse->nMem++;
- buildIndexProbe(v, nCol, pIdx);
- if( bRev ){
- int op = topEq ? OP_MoveLe : OP_MoveLt;
- sqlite3VdbeAddOp(v, op, iIdxCur, nxt);
- }else{
- sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 1);
- }
- }else if( bRev ){
- sqlite3VdbeAddOp(v, OP_Last, iIdxCur, brk);
- }
-
- /* Generate the start key. This is the key that defines the lower
- ** bound on the search. There is no start key if there are no
- ** equality terms and if there is no "X>..." term. In
- ** that case, generate a "Rewind" instruction in place of the
- ** start key search.
- **
- ** 2002-Dec-04: In the case of a reverse-order search, the so-called
- ** "start" key really ends up being used as the termination key.
- */
- if( btmLimit ){
- Expr *pX;
- int k = pIdx->aiColumn[j];
- pTerm = findTerm(&wc, iCur, k, notReady, btmOp, pIdx);
- assert( pTerm!=0 );
- pX = pTerm->pExpr;
- assert( (pTerm->flags & TERM_CODED)==0 );
- sqlite3ExprCode(pParse, pX->pRight);
- sqlite3VdbeAddOp(v, OP_IsNull, -(nEq+1), nxt);
- btmEq = pTerm->eOperator & (WO_LE|WO_GE);
- disableTerm(pLevel, pTerm);
- }else{
- btmEq = 1;
- }
- if( nEq>0 || btmLimit ){
- int nCol = nEq + btmLimit;
- buildIndexProbe(v, nCol, pIdx);
- if( bRev ){
- pLevel->iMem = pParse->nMem++;
- sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 1);
- testOp = OP_IdxLT;
- }else{
- int op = btmEq ? OP_MoveGe : OP_MoveGt;
- sqlite3VdbeAddOp(v, op, iIdxCur, nxt);
- }
- }else if( bRev ){
- testOp = OP_Noop;
- }else{
- sqlite3VdbeAddOp(v, OP_Rewind, iIdxCur, brk);
- }
-
- /* Generate the the top of the loop. If there is a termination
- ** key we have to test for that key and abort at the top of the
- ** loop.
- */
- start = sqlite3VdbeCurrentAddr(v);
- if( testOp!=OP_Noop ){
- sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0);
- sqlite3VdbeAddOp(v, testOp, iIdxCur, nxt);
- if( (topEq && !bRev) || (!btmEq && bRev) ){
- sqlite3VdbeChangeP3(v, -1, "+", P3_STATIC);
- }
- }
- if( topLimit | btmLimit ){
- sqlite3VdbeAddOp(v, OP_Column, iIdxCur, nEq);
- sqlite3VdbeAddOp(v, OP_IsNull, 1, cont);
- }
- if( !omitTable ){
- sqlite3VdbeAddOp(v, OP_IdxRowid, iIdxCur, 0);
- sqlite3VdbeAddOp(v, OP_MoveGe, iCur, 0);
- }
-
- /* Record the instruction used to terminate the loop.
- */
- pLevel->op = bRev ? OP_Prev : OP_Next;
- pLevel->p1 = iIdxCur;
- pLevel->p2 = start;
- }else if( pLevel->flags & WHERE_COLUMN_EQ ){
- /* Case 4: There is an index and all terms of the WHERE clause that
- ** refer to the index using the "==" or "IN" operators.
- */
- int start;
- int nEq = pLevel->nEq;
-
- /* Generate code to evaluate all constraint terms using == or IN
- ** and leave the values of those terms on the stack.
- */
- codeAllEqualityTerms(pParse, pLevel, &wc, notReady);
- nxt = pLevel->nxt;
-
- /* Generate a single key that will be used to both start and terminate
- ** the search
- */
- buildIndexProbe(v, nEq, pIdx);
- sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 0);
-
- /* Generate code (1) to move to the first matching element of the table.
- ** Then generate code (2) that jumps to "nxt" after the cursor is past
- ** the last matching element of the table. The code (1) is executed
- ** once to initialize the search, the code (2) is executed before each
- ** iteration of the scan to see if the scan has finished. */
- if( bRev ){
- /* Scan in reverse order */
- sqlite3VdbeAddOp(v, OP_MoveLe, iIdxCur, nxt);
- start = sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0);
- sqlite3VdbeAddOp(v, OP_IdxLT, iIdxCur, nxt);
- pLevel->op = OP_Prev;
- }else{
- /* Scan in the forward order */
- sqlite3VdbeAddOp(v, OP_MoveGe, iIdxCur, nxt);
- start = sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0);
- sqlite3VdbeOp3(v, OP_IdxGE, iIdxCur, nxt, "+", P3_STATIC);
- pLevel->op = OP_Next;
- }
- if( !omitTable ){
- sqlite3VdbeAddOp(v, OP_IdxRowid, iIdxCur, 0);
- sqlite3VdbeAddOp(v, OP_MoveGe, iCur, 0);
- }
- pLevel->p1 = iIdxCur;
- pLevel->p2 = start;
- }else{
- /* Case 5: 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 + sqlite3VdbeAddOp(v, OP_Rewind, iCur, brk);
- }
- notReady &= ~getMask(&maskSet, iCur);
- sqlite3VdbeAddOp(v, OP_StackDepth, -1, 0);
-
- /* 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;
- 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, 1);
- 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);
- sqlite3VdbeAddOp(v, OP_MemInt, 1, pLevel->iLeftJoin);
- VdbeComment((v, "# record LEFT JOIN hit"));
- for(pTerm=wc.a, j=0; j<wc.nTerm; j++, pTerm++){
- if( pTerm->flags & (TERM_VIRTUAL|TERM_CODED) ) continue;
- if( (pTerm->prereqAll & notReady)!=0 ) continue;
- assert( pTerm->pExpr );
- sqlite3ExprIfFalse(pParse, pTerm->pExpr, cont, 1);
- 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++] = ' ';
- }
- 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){
- Vdbe *v = pWInfo->pParse->pVdbe;
- int i;
- WhereLevel *pLevel;
- SrcList *pTabList = pWInfo->pTabList;
-
- /* Generate loop termination code.
- */
- for(i=pTabList->nSrc-1; i>=0; i--){
- pLevel = &pWInfo->a[i];
- sqlite3VdbeResolveLabel(v, pLevel->cont);
- if( pLevel->op!=OP_Noop ){
- sqlite3VdbeAddOp(v, pLevel->op, pLevel->p1, pLevel->p2);
- }
- if( pLevel->nIn ){
- WhereLevel::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);
- sqlite3VdbeAddOp(v, OP_Next, pIn->iCur, pIn->topAddr);
- sqlite3VdbeJumpHere(v, pIn->topAddr-1);
- }
- sqlite3_free(pLevel->aInLoop);
- }
- sqlite3VdbeResolveLabel(v, pLevel->brk);
- if( pLevel->iLeftJoin ){
- int addr;
- addr = sqlite3VdbeAddOp(v, OP_IfMemPos, pLevel->iLeftJoin, 0);
- sqlite3VdbeAddOp(v, OP_NullRow, pTabList->a[i].iCursor, 0);
- if( pLevel->iIdxCur>=0 ){
- sqlite3VdbeAddOp(v, OP_NullRow, pLevel->iIdxCur, 0);
- }
- sqlite3VdbeAddOp(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++){
- SrcList::SrcList_item *pTabItem = &pTabList->a[pLevel->iFrom];
- Table *pTab = pTabItem->pTab;
- assert( pTab!=0 );
- if( pTab->isEphem || pTab->pSelect ) continue;
- if( (pLevel->flags & WHERE_IDX_ONLY)==0 ){
- sqlite3VdbeAddOp(v, OP_Close, pTabItem->iCursor, 0);
- }
- if( pLevel->pIdx!=0 ){
- sqlite3VdbeAddOp(v, OP_Close, pLevel->iIdxCur, 0);
- }
-
- /* 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;
-}