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Enhance the query flattener to handle subqueries that are joins.

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All regressions pass but new tests need to be added before release.
Ticket #272. (CVS 948)

FossilOrigin-Name: ad57693e9f1b83a8cc4d028264b35018a9a4a701
This commit is contained in:
drh
2003-05-02 16:04:17 +00:00
parent 6a3ea0e6ef
commit c31c2eb82c
4 changed files with 113 additions and 24 deletions
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79
src/select.c
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@@ -12,7 +12,7 @@
** This file contains C code routines that are called by the parser
** to handle SELECT statements in SQLite.
**
** $Id: select.c,v 1.136 2003/05/02 14:32:13 drh Exp $
** $Id: select.c,v 1.137 2003/05/02 16:04:17 drh Exp $
*/
#include "sqliteInt.h"
@@ -1555,7 +1555,7 @@ substExprList(ExprList *pList, int iTable, ExprList *pEList){
**
** (2) The subquery is not an aggregate or the outer query is not a join.
**
** (3) The subquery is not a join.
** (3) (No longer a restriction)
**
** (4) The subquery is not DISTINCT or the outer query is not a join.
**
@@ -1613,7 +1613,7 @@ static int flattenSubquery(
if( subqueryIsAgg && pSrc->nSrc>1 ) return 0;
pSubSrc = pSub->pSrc;
assert( pSubSrc );
if( pSubSrc->nSrc!=1 ) return 0;
if( pSubSrc->nSrc==0 ) return 0;
if( (pSub->isDistinct || pSub->nLimit>=0) && (pSrc->nSrc>1 || isAgg) ){
return 0;
}
@@ -1623,8 +1623,52 @@ static int flattenSubquery(
/* If we reach this point, it means flattening is permitted for the
** iFrom-th entry of the FROM clause in the outer query.
*/
/* Move all of the FROM elements of the subquery into the
** the FROM clause of the outer query. Before doing this, remember
** the cursor number for the original outer query FROM element in
** iParent. The iParent cursor will never be used. Subsequent code
** will scan expressions looking for iParent references and replace
** those references with expressions that resolve to the subquery FROM
** elements we are now copying in.
*/
iParent = pSrc->a[iFrom].iCursor;
pSrc->a[iFrom].iCursor = pSubSrc->a[0].iCursor;
{
int nSubSrc = pSubSrc->nSrc;
if( pSrc->a[iFrom].pTab && pSrc->a[iFrom].pTab->isTransient ){
sqliteDeleteTable(0, pSrc->a[iFrom].pTab);
}
sqliteFree(pSrc->a[iFrom].zName);
sqliteFree(pSrc->a[iFrom].zAlias);
if( nSubSrc>1 ){
int extra = nSubSrc - 1;
for(i=1; i<nSubSrc; i++){
pSrc = sqliteSrcListAppend(pSrc, 0, 0);
}
p->pSrc = pSrc;
for(i=pSrc->nSrc-1; i-extra>=iFrom; i--){
pSrc->a[i] = pSrc->a[i-extra];
}
}
for(i=0; i<nSubSrc; i++){
pSrc->a[i+iFrom] = pSubSrc->a[i];
memset(&pSubSrc->a[i], 0, sizeof(pSubSrc->a[i]));
}
}
/* Now begin substituting subquery result set expressions for
** references to the iParent in the outer query.
**
** Example:
**
** SELECT a+5, b*10 FROM (SELECT x*3 AS a, y+10 AS b FROM t1) WHERE a>b;
** \ \_____________ subquery __________/ /
** \_____________________ outer query ______________________________/
**
** We look at every expression in the outer query and every place we see
** "a" we substitute "x*3" and every place we see "b" we substitute "y+10".
*/
substExprList(p->pEList, iParent, pSub->pEList);
pList = p->pEList;
for(i=0; i<pList->nExpr; i++){
@@ -1672,8 +1716,15 @@ static int flattenSubquery(
p->pWhere = sqliteExpr(TK_AND, p->pWhere, pWhere, 0);
}
}
/* The flattened query is distinct if either the inner or the
** outer query is distinct.
*/
p->isDistinct = p->isDistinct || pSub->isDistinct;
/* Transfer the limit expression from the subquery to the outer
** query.
*/
if( pSub->nLimit>=0 ){
if( p->nLimit<0 ){
p->nLimit = pSub->nLimit;
@@ -1683,14 +1734,9 @@ static int flattenSubquery(
}
p->nOffset += pSub->nOffset;
if( pSrc->a[iFrom].pTab && pSrc->a[iFrom].pTab->isTransient ){
sqliteDeleteTable(0, pSrc->a[iFrom].pTab);
}
pSrc->a[iFrom].pTab = pSubSrc->a[0].pTab;
pSubSrc->a[0].pTab = 0;
assert( pSrc->a[iFrom].pSelect==pSub );
pSrc->a[iFrom].pSelect = pSubSrc->a[0].pSelect;
pSubSrc->a[0].pSelect = 0;
/* Finially, delete what is left of the subquery and return
** success.
*/
sqliteSelectDelete(pSub);
return 1;
}
@@ -2079,19 +2125,24 @@ int sqliteSelect(
*/
for(i=0; i<pTabList->nSrc; i++){
const char *zSavedAuthContext;
int needRestoreContext;
if( pTabList->a[i].pSelect==0 ) continue;
if( pTabList->a[i].zName!=0 ){
zSavedAuthContext = pParse->zAuthContext;
pParse->zAuthContext = pTabList->a[i].zName;
needRestoreContext = 1;
}else{
needRestoreContext = 0;
}
sqliteSelect(pParse, pTabList->a[i].pSelect, SRT_TempTable,
pTabList->a[i].iCursor, p, i, &isAgg);
if( pTabList->a[i].zName!=0 ){
if( needRestoreContext ){
pParse->zAuthContext = zSavedAuthContext;
}
pTabList = p->pSrc;
pWhere = p->pWhere;
if( eDest==SRT_Callback ){
if( eDest!=SRT_Union && eDest!=SRT_Except && eDest!=SRT_Discard ){
pOrderBy = p->pOrderBy;
}
pGroupBy = p->pGroupBy;