/*
** Commute a comparison operator. Expressions of the form "X op Y"
** are converted into "Y op X".
**
** If left/right precedence rules come into play when determining the
** collating sequence, then COLLATE operators are adjusted to ensure
** that the collating sequence does not change. For example:
** "Y collate NOCASE op X" becomes "X op Y" 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_Collate flag
** is not commuted.
*/
static void exprCommute(Parse *pParse, Expr *pExpr){
u16 expRight = (pExpr->pRight->flags & EP_Collate);
u16 expLeft = (pExpr->pLeft->flags & EP_Collate);
assert( allowedOp(pExpr->op) && pExpr->op!=TK_IN );
if( expRight==expLeft ){
/* Either X and Y both have COLLATE operator or neither do */
if( expRight ){
/* Both X and Y have COLLATE operators. Make sure X is always
** used by clearing the EP_Collate flag from Y. */
pExpr->pRight->flags &= ~EP_Collate;
}else if( sqlite3ExprCollSeq(pParse, pExpr->pLeft)!=0 ){
/* Neither X nor Y have COLLATE operators, but X has a non-default
** collating sequence. So add the EP_Collate marker on X to cause
** it to be searched first. */
pExpr->pLeft->flags |= EP_Collate;
}
}
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;
}
}
/*
** The input to this routine is an ExprInfo structure with only the
** "p" field filled in. The job of this routine is to analyze the
** subexpression and populate all the other fields of the ExprInfo
** structure.
*/
static void exprAnalyze(SrcList *pSrc, ExprMaskSet *pMaskSet, ExprInfo *pInfo){
Expr *pExpr = pInfo->p;
pInfo->prereqLeft = exprTableUsage(pMaskSet, pExpr->pLeft);
pInfo->prereqRight = exprTableUsage(pMaskSet, pExpr->pRight);
pInfo->prereqAll = exprTableUsage(pMaskSet, pExpr);
pInfo->indexable = 0;
pInfo->idxLeft = -1;
pInfo->idxRight = -1;
if( allowedOp(pExpr->op) && (pInfo->prereqRight & pInfo->prereqLeft)==0 ){
if( pExpr->pRight && pExpr->pRight->op==TK_COLUMN ){
pInfo->idxRight = pExpr->pRight->iTable;
pInfo->indexable = 1;
}
if( pExpr->pLeft->op==TK_COLUMN ){
pInfo->idxLeft = pExpr->pLeft->iTable;
pInfo->indexable = 1;
}
}
if( pInfo->indexable ){
assert( pInfo->idxLeft!=pInfo->idxRight );
/* We want the expression to be of the form "X = expr", not "expr = X".
** So flip it over if necessary. If the expression is "X = Y", then
** we want Y to come from an earlier table than X.
**
** The collating sequence rule is to always choose the left expression.
** So if we do a flip, we also have to move the collating sequence.
*/
if( tableOrder(pSrc,pInfo->idxLeft)<tableOrder(pSrc,pInfo->idxRight) ){
assert( pExpr->op!=TK_IN );
SWAP(CollSeq*,pExpr->pRight->pColl,pExpr->pLeft->pColl);
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;
}
SWAP(unsigned, pInfo->prereqLeft, pInfo->prereqRight);
SWAP(short int, pInfo->idxLeft, pInfo->idxRight);
}
/*
** The input to this routine is an ExprInfo structure with only the
** "p" field filled in. The job of this routine is to analyze the
** subexpression and populate all the other fields of the ExprInfo
** structure.
*/
static void exprAnalyze(ExprMaskSet *pMaskSet, ExprInfo *pInfo){
Expr *pExpr = pInfo->p;
pInfo->prereqLeft = exprTableUsage(pMaskSet, pExpr->pLeft);
pInfo->prereqRight = exprTableUsage(pMaskSet, pExpr->pRight);
pInfo->prereqAll = exprTableUsage(pMaskSet, pExpr);
pInfo->indexable = 0;
pInfo->idxLeft = -1;
pInfo->idxRight = -1;
if( allowedOp(pExpr->op) && (pInfo->prereqRight & pInfo->prereqLeft)==0 ){
if( pExpr->pRight && pExpr->pRight->op==TK_COLUMN ){
pInfo->idxRight = pExpr->pRight->iTable;
pInfo->indexable = 1;
}
if( pExpr->pLeft->op==TK_COLUMN ){
pInfo->idxLeft = pExpr->pLeft->iTable;
pInfo->indexable = 1;
}
}
}
/*
** Translate from TK_xx operator to WO_xx bitmask.
*/
static u16 operatorMask(int op){
u16 c;
assert( allowedOp(op) );
if( op==TK_IN ){
c = WO_IN;
}else if( op==TK_ISNULL ){
c = WO_ISNULL;
}else if( op==TK_IS ){
c = WO_IS;
}else{
assert( (WO_EQ<<(op-TK_EQ)) < 0x7fff );
c = (u16)(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 );
assert( op!=TK_IS || c==WO_IS );
return c;
}
/*
** 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
** term of the form "Y <op> X" is added to the WHERE clause and
** analyzed separately. The original term is marked with TERM_COPIED
** and the new term is marked with TERM_DYNAMIC (because it's pExpr
** needs to be freed with the WhereClause) and TERM_VIRTUAL (because it
** is a commuted copy of a prior term.) The original term has nChild=1
** and the copy has idxParent set to the index of the original term.
*/
static void exprAnalyze(
SrcList *pSrc, /* the FROM clause */
WhereClause *pWC, /* the WHERE clause */
int idxTerm /* Index of the term to be analyzed */
){
WhereInfo *pWInfo = pWC->pWInfo; /* WHERE clause processing context */
WhereTerm *pTerm; /* The term to be analyzed */
WhereMaskSet *pMaskSet; /* Set of table index masks */
Expr *pExpr; /* The expression to be analyzed */
Bitmask prereqLeft; /* Prerequesites of the pExpr->pLeft */
Bitmask prereqAll; /* Prerequesites of pExpr */
Bitmask extraRight = 0; /* Extra dependencies on LEFT JOIN */
Expr *pStr1 = 0; /* RHS of LIKE/GLOB operator */
int isComplete = 0; /* RHS of LIKE/GLOB ends with wildcard */
int noCase = 0; /* uppercase equivalent to lowercase */
int op; /* Top-level operator. pExpr->op */
Parse *pParse = pWInfo->pParse; /* Parsing context */
sqlite3 *db = pParse->db; /* Database connection */
if( db->mallocFailed ){
return;
}
pTerm = &pWC->a[idxTerm];
pMaskSet = &pWInfo->sMaskSet;
pExpr = pTerm->pExpr;
assert( pExpr->op!=TK_AS && pExpr->op!=TK_COLLATE );
prereqLeft = sqlite3WhereExprUsage(pMaskSet, pExpr->pLeft);
op = pExpr->op;
if( op==TK_IN ){
assert( pExpr->pRight==0 );
if( ExprHasProperty(pExpr, EP_xIsSelect) ){
pTerm->prereqRight = exprSelectUsage(pMaskSet, pExpr->x.pSelect);
}else{
pTerm->prereqRight = sqlite3WhereExprListUsage(pMaskSet, pExpr->x.pList);
}
}else if( op==TK_ISNULL ){
pTerm->prereqRight = 0;
}else{
pTerm->prereqRight = sqlite3WhereExprUsage(pMaskSet, pExpr->pRight);
}
prereqAll = sqlite3WhereExprUsage(pMaskSet, pExpr);
if( ExprHasProperty(pExpr, EP_FromJoin) ){
Bitmask x = sqlite3WhereGetMask(pMaskSet, pExpr->iRightJoinTable);
prereqAll |= x;
extraRight = x-1; /* ON clause terms may not be used with an index
** on left table of a LEFT JOIN. Ticket #3015 */
}
pTerm->prereqAll = prereqAll;
pTerm->leftCursor = -1;
pTerm->iParent = -1;
pTerm->eOperator = 0;
if( allowedOp(op) ){
Expr *pLeft = sqlite3ExprSkipCollate(pExpr->pLeft);
Expr *pRight = sqlite3ExprSkipCollate(pExpr->pRight);
u16 opMask = (pTerm->prereqRight & prereqLeft)==0 ? WO_ALL : WO_EQUIV;
if( pLeft->op==TK_COLUMN ){
pTerm->leftCursor = pLeft->iTable;
pTerm->u.leftColumn = pLeft->iColumn;
pTerm->eOperator = operatorMask(op) & opMask;
}
if( op==TK_IS ) pTerm->wtFlags |= TERM_IS;
if( pRight && pRight->op==TK_COLUMN ){
WhereTerm *pNew;
Expr *pDup;
u16 eExtraOp = 0; /* Extra bits for pNew->eOperator */
if( pTerm->leftCursor>=0 ){
int idxNew;
pDup = sqlite3ExprDup(db, pExpr, 0);
if( db->mallocFailed ){
sqlite3ExprDelete(db, pDup);
return;
}
idxNew = whereClauseInsert(pWC, pDup, TERM_VIRTUAL|TERM_DYNAMIC);
if( idxNew==0 ) return;
pNew = &pWC->a[idxNew];
markTermAsChild(pWC, idxNew, idxTerm);
if( op==TK_IS ) pNew->wtFlags |= TERM_IS;
pTerm = &pWC->a[idxTerm];
pTerm->wtFlags |= TERM_COPIED;
if( termIsEquivalence(pParse, pDup) ){
pTerm->eOperator |= WO_EQUIV;
eExtraOp = WO_EQUIV;
}
}else{
pDup = pExpr;
pNew = pTerm;
}
exprCommute(pParse, pDup);
pLeft = sqlite3ExprSkipCollate(pDup->pLeft);
pNew->leftCursor = pLeft->iTable;
pNew->u.leftColumn = pLeft->iColumn;
testcase( (prereqLeft | extraRight) != prereqLeft );
pNew->prereqRight = prereqLeft | extraRight;
pNew->prereqAll = prereqAll;
pNew->eOperator = (operatorMask(pDup->op) + eExtraOp) & opMask;
}
}
#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. For example:
**
** a BETWEEN b AND c
**
** is converted into:
**
** (a BETWEEN b AND c) AND (a>=b) AND (a<=c)
**
** The two new terms are added onto the end of the WhereClause object.
** The new terms are "dynamic" and are children of the original BETWEEN
** term. That means that if the BETWEEN term is coded, the children are
** skipped. Or, if the children are satisfied by an index, the original
** BETWEEN term is skipped.
*/
else if( pExpr->op==TK_BETWEEN && pWC->op==TK_AND ){
ExprList *pList = pExpr->x.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 = sqlite3PExpr(pParse, ops[i],
sqlite3ExprDup(db, pExpr->pLeft, 0),
sqlite3ExprDup(db, pList->a[i].pExpr, 0), 0);
transferJoinMarkings(pNewExpr, pExpr);
idxNew = whereClauseInsert(pWC, pNewExpr, TERM_VIRTUAL|TERM_DYNAMIC);
testcase( idxNew==0 );
exprAnalyze(pSrc, pWC, idxNew);
pTerm = &pWC->a[idxTerm];
markTermAsChild(pWC, idxNew, idxTerm);
}
}
#endif /* SQLITE_OMIT_BETWEEN_OPTIMIZATION */
#if !defined(SQLITE_OMIT_OR_OPTIMIZATION) && !defined(SQLITE_OMIT_SUBQUERY)
/* Analyze a term that is composed of two or more subterms connected by
** an OR operator.
*/
else if( pExpr->op==TK_OR ){
assert( pWC->op==TK_AND );
exprAnalyzeOrTerm(pSrc, pWC, idxTerm);
pTerm = &pWC->a[idxTerm];
}
#endif /* SQLITE_OMIT_OR_OPTIMIZATION */
#ifndef SQLITE_OMIT_LIKE_OPTIMIZATION
/* Add constraints to reduce the search space on a LIKE or GLOB
** operator.
**
** A like pattern of the form "x LIKE 'aBc%'" is changed into constraints
**
** x>='ABC' AND x<'abd' AND x LIKE 'aBc%'
**
** The last character of the prefix "abc" is incremented to form the
** termination condition "abd". If case is not significant (the default
** for LIKE) then the lower-bound is made all uppercase and the upper-
** bound is made all lowercase so that the bounds also work when comparing
** BLOBs.
*/
if( pWC->op==TK_AND
&& isLikeOrGlob(pParse, pExpr, &pStr1, &isComplete, &noCase)
){
Expr *pLeft; /* LHS of LIKE/GLOB operator */
Expr *pStr2; /* Copy of pStr1 - RHS of LIKE/GLOB operator */
Expr *pNewExpr1;
Expr *pNewExpr2;
int idxNew1;
int idxNew2;
const char *zCollSeqName; /* Name of collating sequence */
const u16 wtFlags = TERM_LIKEOPT | TERM_VIRTUAL | TERM_DYNAMIC;
pLeft = pExpr->x.pList->a[1].pExpr;
pStr2 = sqlite3ExprDup(db, pStr1, 0);
/* Convert the lower bound to upper-case and the upper bound to
** lower-case (upper-case is less than lower-case in ASCII) so that
** the range constraints also work for BLOBs
*/
if( noCase && !pParse->db->mallocFailed ){
int i;
char c;
pTerm->wtFlags |= TERM_LIKE;
for(i=0; (c = pStr1->u.zToken[i])!=0; i++){
pStr1->u.zToken[i] = sqlite3Toupper(c);
pStr2->u.zToken[i] = sqlite3Tolower(c);
}
}
if( !db->mallocFailed ){
u8 c, *pC; /* Last character before the first wildcard */
pC = (u8*)&pStr2->u.zToken[sqlite3Strlen30(pStr2->u.zToken)-1];
c = *pC;
if( noCase ){
/* The point is to increment the last character before the first
** wildcard. But if we increment '@', that will push it into the
** alphabetic range where case conversions will mess up the
** inequality. To avoid this, make sure to also run the full
** LIKE on all candidate expressions by clearing the isComplete flag
*/
if( c=='A'-1 ) isComplete = 0;
c = sqlite3UpperToLower[c];
}
*pC = c + 1;
}
zCollSeqName = noCase ? "NOCASE" : "BINARY";
pNewExpr1 = sqlite3ExprDup(db, pLeft, 0);
pNewExpr1 = sqlite3PExpr(pParse, TK_GE,
sqlite3ExprAddCollateString(pParse,pNewExpr1,zCollSeqName),
pStr1, 0);
transferJoinMarkings(pNewExpr1, pExpr);
idxNew1 = whereClauseInsert(pWC, pNewExpr1, wtFlags);
testcase( idxNew1==0 );
exprAnalyze(pSrc, pWC, idxNew1);
pNewExpr2 = sqlite3ExprDup(db, pLeft, 0);
pNewExpr2 = sqlite3PExpr(pParse, TK_LT,
sqlite3ExprAddCollateString(pParse,pNewExpr2,zCollSeqName),
pStr2, 0);
transferJoinMarkings(pNewExpr2, pExpr);
idxNew2 = whereClauseInsert(pWC, pNewExpr2, wtFlags);
testcase( idxNew2==0 );
exprAnalyze(pSrc, pWC, idxNew2);
pTerm = &pWC->a[idxTerm];
if( isComplete ){
markTermAsChild(pWC, idxNew1, idxTerm);
markTermAsChild(pWC, idxNew2, idxTerm);
}
}
#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->x.pList->a[0].pExpr;
pLeft = pExpr->x.pList->a[1].pExpr;
prereqExpr = sqlite3WhereExprUsage(pMaskSet, pRight);
prereqColumn = sqlite3WhereExprUsage(pMaskSet, pLeft);
if( (prereqExpr & prereqColumn)==0 ){
Expr *pNewExpr;
pNewExpr = sqlite3PExpr(pParse, TK_MATCH,
0, sqlite3ExprDup(db, pRight, 0), 0);
idxNew = whereClauseInsert(pWC, pNewExpr, TERM_VIRTUAL|TERM_DYNAMIC);
testcase( idxNew==0 );
pNewTerm = &pWC->a[idxNew];
pNewTerm->prereqRight = prereqExpr;
pNewTerm->leftCursor = pLeft->iTable;
pNewTerm->u.leftColumn = pLeft->iColumn;
pNewTerm->eOperator = WO_MATCH;
markTermAsChild(pWC, idxNew, idxTerm);
pTerm = &pWC->a[idxTerm];
pTerm->wtFlags |= TERM_COPIED;
pNewTerm->prereqAll = pTerm->prereqAll;
}
}
#endif /* SQLITE_OMIT_VIRTUALTABLE */
#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
/* When sqlite_stat3 histogram data is available an operator of the
** form "x IS NOT NULL" can sometimes be evaluated more efficiently
** as "x>NULL" if x is not an INTEGER PRIMARY KEY. So construct a
** virtual term of that form.
**
** Note that the virtual term must be tagged with TERM_VNULL.
*/
if( pExpr->op==TK_NOTNULL
&& pExpr->pLeft->op==TK_COLUMN
&& pExpr->pLeft->iColumn>=0
&& OptimizationEnabled(db, SQLITE_Stat34)
){
Expr *pNewExpr;
Expr *pLeft = pExpr->pLeft;
int idxNew;
WhereTerm *pNewTerm;
pNewExpr = sqlite3PExpr(pParse, TK_GT,
sqlite3ExprDup(db, pLeft, 0),
sqlite3PExpr(pParse, TK_NULL, 0, 0, 0), 0);
idxNew = whereClauseInsert(pWC, pNewExpr,
TERM_VIRTUAL|TERM_DYNAMIC|TERM_VNULL);
if( idxNew ){
pNewTerm = &pWC->a[idxNew];
pNewTerm->prereqRight = 0;
pNewTerm->leftCursor = pLeft->iTable;
pNewTerm->u.leftColumn = pLeft->iColumn;
pNewTerm->eOperator = WO_GT;
markTermAsChild(pWC, idxNew, idxTerm);
pTerm = &pWC->a[idxTerm];
pTerm->wtFlags |= TERM_COPIED;
pNewTerm->prereqAll = pTerm->prereqAll;
}
}
#endif /* SQLITE_ENABLE_STAT3_OR_STAT4 */
/* Prevent ON clause terms of a LEFT JOIN from being used to drive
** an index for tables to the left of the join.
*/
pTerm->prereqRight |= extraRight;
}
/*
** Analyze a term that consists of two or more OR-connected
** subterms. So in:
**
** ... WHERE (a=5) AND (b=7 OR c=9 OR d=13) AND (d=13)
** ^^^^^^^^^^^^^^^^^^^^
**
** This routine analyzes terms such as the middle term in the above example.
** A WhereOrTerm object is computed and attached to the term under
** analysis, regardless of the outcome of the analysis. Hence:
**
** WhereTerm.wtFlags |= TERM_ORINFO
** WhereTerm.u.pOrInfo = a dynamically allocated WhereOrTerm object
**
** The term being analyzed must have two or more of OR-connected subterms.
** A single subterm might be a set of AND-connected sub-subterms.
** Examples of terms under analysis:
**
** (A) t1.x=t2.y OR t1.x=t2.z OR t1.y=15 OR t1.z=t3.a+5
** (B) x=expr1 OR expr2=x OR x=expr3
** (C) t1.x=t2.y OR (t1.x=t2.z AND t1.y=15)
** (D) x=expr1 OR (y>11 AND y<22 AND z LIKE '*hello*')
** (E) (p.a=1 AND q.b=2 AND r.c=3) OR (p.x=4 AND q.y=5 AND r.z=6)
** (F) x>A OR (x=A AND y>=B)
**
** CASE 1:
**
** If all subterms are of the form T.C=expr for some single column of C and
** a single table T (as shown in example B above) then create a new virtual
** term that is an equivalent IN expression. In other words, if the term
** being analyzed is:
**
** x = expr1 OR expr2 = x OR x = expr3
**
** then create a new virtual term like this:
**
** x IN (expr1,expr2,expr3)
**
** CASE 2:
**
** If there are exactly two disjuncts and one side has x>A and the other side
** has x=A (for the same x and A) then add a new virtual conjunct term to the
** WHERE clause of the form "x>=A". Example:
**
** x>A OR (x=A AND y>B) adds: x>=A
**
** The added conjunct can sometimes be helpful in query planning.
**
** CASE 3:
**
** If all subterms are indexable by a single table T, then set
**
** WhereTerm.eOperator = WO_OR
** WhereTerm.u.pOrInfo->indexable |= the cursor number for table T
**
** A subterm is "indexable" if it is of the form
** "T.C <op> <expr>" where C is any column of table T and
** <op> is one of "=", "<", "<=", ">", ">=", "IS NULL", or "IN".
** A subterm is also indexable if it is an AND of two or more
** subsubterms at least one of which is indexable. Indexable AND
** subterms have their eOperator set to WO_AND and they have
** u.pAndInfo set to a dynamically allocated WhereAndTerm object.
**
** From another point of view, "indexable" means that the subterm could
** potentially be used with an index if an appropriate index exists.
** This analysis does not consider whether or not the index exists; that
** is decided elsewhere. This analysis only looks at whether subterms
** appropriate for indexing exist.
**
** All examples A through E above satisfy case 3. But if a term
** also satisfies case 1 (such as B) we know that the optimizer will
** always prefer case 1, so in that case we pretend that case 3 is not
** satisfied.
**
** It might be the case that multiple tables are indexable. For example,
** (E) above is indexable on tables P, Q, and R.
**
** Terms that satisfy case 3 are candidates for lookup by using
** separate indices to find rowids for each subterm and composing
** the union of all rowids using a RowSet object. This is similar
** to "bitmap indices" in other database engines.
**
** OTHERWISE:
**
** If none of cases 1, 2, or 3 apply, then leave the eOperator set to
** zero. This term is not useful for search.
*/
static void exprAnalyzeOrTerm(
SrcList *pSrc, /* the FROM clause */
WhereClause *pWC, /* the complete WHERE clause */
int idxTerm /* Index of the OR-term to be analyzed */
){
WhereInfo *pWInfo = pWC->pWInfo; /* WHERE clause processing context */
Parse *pParse = pWInfo->pParse; /* Parser context */
sqlite3 *db = pParse->db; /* Database connection */
WhereTerm *pTerm = &pWC->a[idxTerm]; /* The term to be analyzed */
Expr *pExpr = pTerm->pExpr; /* The expression of the term */
int i; /* Loop counters */
WhereClause *pOrWc; /* Breakup of pTerm into subterms */
WhereTerm *pOrTerm; /* A Sub-term within the pOrWc */
WhereOrInfo *pOrInfo; /* Additional information associated with pTerm */
Bitmask chngToIN; /* Tables that might satisfy case 1 */
Bitmask indexable; /* Tables that are indexable, satisfying case 2 */
/*
** Break the OR clause into its separate subterms. The subterms are
** stored in a WhereClause structure containing within the WhereOrInfo
** object that is attached to the original OR clause term.
*/
assert( (pTerm->wtFlags & (TERM_DYNAMIC|TERM_ORINFO|TERM_ANDINFO))==0 );
assert( pExpr->op==TK_OR );
pTerm->u.pOrInfo = pOrInfo = sqlite3DbMallocZero(db, sizeof(*pOrInfo));
if( pOrInfo==0 ) return;
pTerm->wtFlags |= TERM_ORINFO;
pOrWc = &pOrInfo->wc;
sqlite3WhereClauseInit(pOrWc, pWInfo);
sqlite3WhereSplit(pOrWc, pExpr, TK_OR);
sqlite3WhereExprAnalyze(pSrc, pOrWc);
if( db->mallocFailed ) return;
assert( pOrWc->nTerm>=2 );
/*
** Compute the set of tables that might satisfy cases 1 or 3.
*/
indexable = ~(Bitmask)0;
chngToIN = ~(Bitmask)0;
for(i=pOrWc->nTerm-1, pOrTerm=pOrWc->a; i>=0 && indexable; i--, pOrTerm++){
if( (pOrTerm->eOperator & WO_SINGLE)==0 ){
WhereAndInfo *pAndInfo;
assert( (pOrTerm->wtFlags & (TERM_ANDINFO|TERM_ORINFO))==0 );
chngToIN = 0;
pAndInfo = sqlite3DbMallocRaw(db, sizeof(*pAndInfo));
if( pAndInfo ){
WhereClause *pAndWC;
WhereTerm *pAndTerm;
int j;
Bitmask b = 0;
pOrTerm->u.pAndInfo = pAndInfo;
pOrTerm->wtFlags |= TERM_ANDINFO;
pOrTerm->eOperator = WO_AND;
pAndWC = &pAndInfo->wc;
sqlite3WhereClauseInit(pAndWC, pWC->pWInfo);
sqlite3WhereSplit(pAndWC, pOrTerm->pExpr, TK_AND);
sqlite3WhereExprAnalyze(pSrc, pAndWC);
pAndWC->pOuter = pWC;
testcase( db->mallocFailed );
if( !db->mallocFailed ){
for(j=0, pAndTerm=pAndWC->a; j<pAndWC->nTerm; j++, pAndTerm++){
assert( pAndTerm->pExpr );
if( allowedOp(pAndTerm->pExpr->op) ){
b |= sqlite3WhereGetMask(&pWInfo->sMaskSet, pAndTerm->leftCursor);
}
}
}
indexable &= b;
}
}else if( pOrTerm->wtFlags & TERM_COPIED ){
/* Skip this term for now. We revisit it when we process the
** corresponding TERM_VIRTUAL term */
}else{
Bitmask b;
b = sqlite3WhereGetMask(&pWInfo->sMaskSet, pOrTerm->leftCursor);
if( pOrTerm->wtFlags & TERM_VIRTUAL ){
WhereTerm *pOther = &pOrWc->a[pOrTerm->iParent];
b |= sqlite3WhereGetMask(&pWInfo->sMaskSet, pOther->leftCursor);
}
indexable &= b;
if( (pOrTerm->eOperator & WO_EQ)==0 ){
chngToIN = 0;
}else{
chngToIN &= b;
}
}
}
/*
** Record the set of tables that satisfy case 3. The set might be
** empty.
*/
pOrInfo->indexable = indexable;
pTerm->eOperator = indexable==0 ? 0 : WO_OR;
/* For a two-way OR, attempt to implementation case 2.
*/
if( indexable && pOrWc->nTerm==2 ){
int iOne = 0;
WhereTerm *pOne;
while( (pOne = whereNthSubterm(&pOrWc->a[0],iOne++))!=0 ){
int iTwo = 0;
WhereTerm *pTwo;
while( (pTwo = whereNthSubterm(&pOrWc->a[1],iTwo++))!=0 ){
whereCombineDisjuncts(pSrc, pWC, pOne, pTwo);
}
}
}
/*
** chngToIN holds a set of tables that *might* satisfy case 1. But
** we have to do some additional checking to see if case 1 really
** is satisfied.
**
** chngToIN will hold either 0, 1, or 2 bits. The 0-bit case means
** that there is no possibility of transforming the OR clause into an
** IN operator because one or more terms in the OR clause contain
** something other than == on a column in the single table. The 1-bit
** case means that every term of the OR clause is of the form
** "table.column=expr" for some single table. The one bit that is set
** will correspond to the common table. We still need to check to make
** sure the same column is used on all terms. The 2-bit case is when
** the all terms are of the form "table1.column=table2.column". It
** might be possible to form an IN operator with either table1.column
** or table2.column as the LHS if either is common to every term of
** the OR clause.
**
** Note that terms of the form "table.column1=table.column2" (the
** same table on both sizes of the ==) cannot be optimized.
*/
if( chngToIN ){
int okToChngToIN = 0; /* True if the conversion to IN is valid */
int iColumn = -1; /* Column index on lhs of IN operator */
int iCursor = -1; /* Table cursor common to all terms */
int j = 0; /* Loop counter */
/* Search for a table and column that appears on one side or the
** other of the == operator in every subterm. That table and column
** will be recorded in iCursor and iColumn. There might not be any
** such table and column. Set okToChngToIN if an appropriate table
** and column is found but leave okToChngToIN false if not found.
*/
for(j=0; j<2 && !okToChngToIN; j++){
pOrTerm = pOrWc->a;
for(i=pOrWc->nTerm-1; i>=0; i--, pOrTerm++){
assert( pOrTerm->eOperator & WO_EQ );
pOrTerm->wtFlags &= ~TERM_OR_OK;
if( pOrTerm->leftCursor==iCursor ){
/* This is the 2-bit case and we are on the second iteration and
** current term is from the first iteration. So skip this term. */
assert( j==1 );
continue;
}
if( (chngToIN & sqlite3WhereGetMask(&pWInfo->sMaskSet,
pOrTerm->leftCursor))==0 ){
/* This term must be of the form t1.a==t2.b where t2 is in the
** chngToIN set but t1 is not. This term will be either preceded
** or follwed by an inverted copy (t2.b==t1.a). Skip this term
** and use its inversion. */
testcase( pOrTerm->wtFlags & TERM_COPIED );
testcase( pOrTerm->wtFlags & TERM_VIRTUAL );
assert( pOrTerm->wtFlags & (TERM_COPIED|TERM_VIRTUAL) );
continue;
}
iColumn = pOrTerm->u.leftColumn;
iCursor = pOrTerm->leftCursor;
break;
}
if( i<0 ){
/* No candidate table+column was found. This can only occur
** on the second iteration */
assert( j==1 );
assert( IsPowerOfTwo(chngToIN) );
assert( chngToIN==sqlite3WhereGetMask(&pWInfo->sMaskSet, iCursor) );
break;
}
testcase( j==1 );
/* We have found a candidate table and column. Check to see if that
** table and column is common to every term in the OR clause */
okToChngToIN = 1;
for(; i>=0 && okToChngToIN; i--, pOrTerm++){
assert( pOrTerm->eOperator & WO_EQ );
if( pOrTerm->leftCursor!=iCursor ){
pOrTerm->wtFlags &= ~TERM_OR_OK;
}else if( pOrTerm->u.leftColumn!=iColumn ){
okToChngToIN = 0;
}else{
int affLeft, affRight;
/* 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)
*/
affRight = sqlite3ExprAffinity(pOrTerm->pExpr->pRight);
affLeft = sqlite3ExprAffinity(pOrTerm->pExpr->pLeft);
if( affRight!=0 && affRight!=affLeft ){
okToChngToIN = 0;
}else{
pOrTerm->wtFlags |= TERM_OR_OK;
}
}
}
}
/* At this point, okToChngToIN is true if original pTerm satisfies
** case 1. In that case, construct a new virtual term that is
** pTerm converted into an IN operator.
*/
if( okToChngToIN ){
Expr *pDup; /* A transient duplicate expression */
ExprList *pList = 0; /* The RHS of the IN operator */
Expr *pLeft = 0; /* The LHS of the IN operator */
Expr *pNew; /* The complete IN operator */
for(i=pOrWc->nTerm-1, pOrTerm=pOrWc->a; i>=0; i--, pOrTerm++){
if( (pOrTerm->wtFlags & TERM_OR_OK)==0 ) continue;
assert( pOrTerm->eOperator & WO_EQ );
assert( pOrTerm->leftCursor==iCursor );
assert( pOrTerm->u.leftColumn==iColumn );
pDup = sqlite3ExprDup(db, pOrTerm->pExpr->pRight, 0);
pList = sqlite3ExprListAppend(pWInfo->pParse, pList, pDup);
pLeft = pOrTerm->pExpr->pLeft;
}
assert( pLeft!=0 );
pDup = sqlite3ExprDup(db, pLeft, 0);
pNew = sqlite3PExpr(pParse, TK_IN, pDup, 0, 0);
if( pNew ){
int idxNew;
transferJoinMarkings(pNew, pExpr);
assert( !ExprHasProperty(pNew, EP_xIsSelect) );
pNew->x.pList = pList;
idxNew = whereClauseInsert(pWC, pNew, TERM_VIRTUAL|TERM_DYNAMIC);
testcase( idxNew==0 );
exprAnalyze(pSrc, pWC, idxNew);
pTerm = &pWC->a[idxTerm];
markTermAsChild(pWC, idxNew, idxTerm);
}else{
sqlite3ExprListDelete(db, pList);
}
pTerm->eOperator = WO_NOOP; /* case 1 trumps case 3 */
}
}
}
