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Enhance the virtual table query planner so that it is able to deal with

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ORDER BY terms that contain COLLATE clauses as long as the specified
collation matches the virtual table.  This is especially important for
UNION ALL since a "COLLATE binary" is added to ORDER BY clauses if no
COLLATE clause exists in the original SQL.

FossilOrigin-Name: 5c3d398d20b86a1558720e995eddf11403aec2d160590571fa9525fe8f6efff9
This commit is contained in:
drh
2021-12-14 20:13:28 +00:00
parent 22f018c938
commit 52576b78f6
4 changed files with 61 additions and 9 deletions
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37
src/where.c
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@@ -1114,6 +1114,10 @@ static sqlite3_index_info *allocateIndexInfo(
sqlite3_index_info *pIdxInfo;
u16 mNoOmit = 0;
assert( pSrc!=0 );
assert( pSrc->pTab!=0 );
assert( IsVirtual(pSrc->pTab) );
/* 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++){
@@ -1140,8 +1144,36 @@ static sqlite3_index_info *allocateIndexInfo(
int n = pOrderBy->nExpr;
for(i=0; i<n; i++){
Expr *pExpr = pOrderBy->a[i].pExpr;
if( pExpr->op!=TK_COLUMN || pExpr->iTable!=pSrc->iCursor ) break;
Expr *pE2;
/* Virtual tables are unable to deal with NULLS FIRST */
if( pOrderBy->a[i].sortFlags & KEYINFO_ORDER_BIGNULL ) break;
/* First case - a direct column references without a COLLATE operator */
if( pExpr->op==TK_COLUMN && pExpr->iTable==pSrc->iCursor ){
assert( pExpr->iColumn>=XN_ROWID && pExpr->iColumn<pSrc->pTab->nCol );
continue;
}
/* 2nd case - a column reference with a COLLATE operator. Only match
** of the COLLATE operator matches the collation of the column. */
if( pExpr->op==TK_COLLATE
&& (pE2 = pExpr->pLeft)->op==TK_COLUMN
&& pE2->iTable==pSrc->iCursor
){
const char *zColl; /* The collating sequence name */
assert( !ExprHasProperty(pExpr, EP_IntValue) );
assert( pExpr->u.zToken!=0 );
assert( pE2->iColumn>=XN_ROWID && pE2->iColumn<pSrc->pTab->nCol );
pExpr->iColumn = pE2->iColumn;
if( pE2->iColumn<0 ) continue; /* Collseq does not matter for rowid */
zColl = sqlite3ColumnColl(&pSrc->pTab->aCol[pE2->iColumn]);
if( zColl==0 ) zColl = sqlite3StrBINARY;
if( sqlite3_stricmp(pExpr->u.zToken, zColl)==0 ) continue;
}
/* No matches cause a break out of the loop */
break;
}
if( i==n){
nOrderBy = n;
@@ -1228,6 +1260,9 @@ static sqlite3_index_info *allocateIndexInfo(
pIdxInfo->nConstraint = j;
for(i=0; i<nOrderBy; i++){
Expr *pExpr = pOrderBy->a[i].pExpr;
assert( pExpr->op==TK_COLUMN
|| (pExpr->op==TK_COLLATE && pExpr->pLeft->op==TK_COLUMN
&& pExpr->iColumn==pExpr->pLeft->iColumn) );
pIdxOrderBy[i].iColumn = pExpr->iColumn;
pIdxOrderBy[i].desc = pOrderBy->a[i].sortFlags & KEYINFO_ORDER_DESC;
}