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Handle compound-select statements originating from VALUES clauses as a

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special case that does not use recursion.

FossilOrigin-Name: 9ce9e43af38e6bc362734463d4bfc40ff0c98f8f
This commit is contained in:
drh
2015-01-05 19:16:42 +00:00
parent a0c01768f0
commit 45f54a5778
5 changed files with 85 additions and 22 deletions
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74
src/select.c
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@@ -2076,6 +2076,66 @@ static int multiSelectOrderBy(
SelectDest *pDest /* What to do with query results */
);
/*
** Error message for when two or more terms of a compound select have different
** size result sets.
*/
static void selectWrongNumTermsError(Parse *pParse, Select *p){
if( p->selFlags & SF_Values ){
sqlite3ErrorMsg(pParse, "all VALUES must have the same number of terms");
}else{
sqlite3ErrorMsg(pParse, "SELECTs to the left and right of %s"
" do not have the same number of result columns", selectOpName(p->op));
}
}
/*
** Handle the special case of a compound-select that originates from a
** VALUES clause. By handling this as a special case, we avoid deep
** recursion, and thus do not need to enforce the SQLITE_LIMIT_COMPOUND_SELECT
** on a VALUES clause.
**
** Because the Select object originates from a VALUES clause:
** (1) It has no LIMIT or OFFSET
** (2) All terms are UNION ALL
** (3) There is no ORDER BY clause
*/
static int multiSelectValues(
Parse *pParse, /* Parsing context */
Select *p, /* The right-most of SELECTs to be coded */
SelectDest *pDest /* What to do with query results */
){
Select *pPrior;
int nExpr = p->pEList->nExpr;
int nRow = 1;
int rc = 0;
assert( p->pNext==0 );
assert( p->selFlags & SF_AllValues );
do{
assert( p->selFlags & SF_Values );
assert( p->op==TK_ALL || (p->op==TK_SELECT && p->pPrior==0) );
assert( p->pLimit==0 );
assert( p->pOffset==0 );
if( p->pEList->nExpr!=nExpr ){
selectWrongNumTermsError(pParse, p);
return 1;
}
if( p->pPrior==0 ) break;
assert( p->pPrior->pNext==p );
p = p->pPrior;
nRow++;
}while(1);
while( p ){
pPrior = p->pPrior;
p->pPrior = 0;
rc = sqlite3Select(pParse, p, pDest);
p->pPrior = pPrior;
if( rc ) break;
p->nSelectRow = nRow;
p = p->pNext;
}
return rc;
}
/*
** This routine is called to process a compound query form from
@@ -2157,17 +2217,19 @@ static int multiSelect(
dest.eDest = SRT_Table;
}
/* Special handling for a compound-select that originates as a VALUES clause.
*/
if( p->selFlags & SF_AllValues ){
rc = multiSelectValues(pParse, p, &dest);
goto multi_select_end;
}
/* Make sure all SELECTs in the statement have the same number of elements
** in their result sets.
*/
assert( p->pEList && pPrior->pEList );
if( p->pEList->nExpr!=pPrior->pEList->nExpr ){
if( p->selFlags & SF_Values ){
sqlite3ErrorMsg(pParse, "all VALUES must have the same number of terms");
}else{
sqlite3ErrorMsg(pParse, "SELECTs to the left and right of %s"
" do not have the same number of result columns", selectOpName(p->op));
}
selectWrongNumTermsError(pParse, p);
rc = 1;
goto multi_select_end;
}