/*
** 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;
}
}
}
/*
** 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);
}
/*
** 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 sqliteExprResolveIds() on the expression. See
** the header comment on that routine for additional information.
** The sqliteExprResolveIds() 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.
*/
static int exprTableUsage(ExprMaskSet *pMaskSet, Expr *p) {
unsigned int mask = 0;
if( p==0 ) return 0;
if( p->op==TK_COLUMN ) {
return getMask(pMaskSet, p->iTable);
}
if( p->pRight ) {
mask = exprTableUsage(pMaskSet, p->pRight);
}
if( p->pLeft ) {
mask |= exprTableUsage(pMaskSet, p->pLeft);
}
if( p->pList ) {
int i;
for(i=0; i<p->pList->nExpr; i++) {
mask |= exprTableUsage(pMaskSet, p->pList->a[i].pExpr);
}
}
return mask;
}
