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Add code to handle recursive CTEs.

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FossilOrigin-Name: a5c2a54a07d35166911abc792008c05dea897742
This commit is contained in:
dan
2014-01-14 20:14:09 +00:00
parent a9f5c13d0c
commit 8ce7184bc2
9 changed files with 262 additions and 33 deletions
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176
src/select.c
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@@ -691,12 +691,26 @@ static void selectInnerLoop(
/* Store the result as data using a unique key.
*/
case SRT_DistTable:
case SRT_Table:
case SRT_EphemTab: {
int r1 = sqlite3GetTempReg(pParse);
testcase( eDest==SRT_Table );
testcase( eDest==SRT_EphemTab );
sqlite3VdbeAddOp3(v, OP_MakeRecord, regResult, nColumn, r1);
#ifndef SQLITE_OMIT_CTE
if( eDest==SRT_DistTable ){
/* If the destination is DistTable, then cursor (iParm+1) is open
** on an ephemeral index. If the current row is already present
** in the index, do not write it to the output. If not, add the
** current row to the index and proceed with writing it to the
** output table as well. */
int addr = sqlite3VdbeCurrentAddr(v) + 4;
sqlite3VdbeAddOp4Int(v, OP_Found, iParm+1, addr, r1, 0);
sqlite3VdbeAddOp2(v, OP_IdxInsert, iParm+1, r1);
assert( pOrderBy==0 );
}
#endif
if( pOrderBy ){
pushOntoSorter(pParse, pOrderBy, p, r1);
}else{
@@ -1729,6 +1743,7 @@ static int multiSelect(
** the last (right-most) SELECT in the series may have an ORDER BY or LIMIT.
*/
assert( p && p->pPrior ); /* Calling function guarantees this much */
assert( p->pRecurse==0 || p->op==TK_ALL || p->op==TK_UNION );
db = pParse->db;
pPrior = p->pPrior;
assert( pPrior->pRightmost!=pPrior );
@@ -1774,12 +1789,82 @@ static int multiSelect(
goto multi_select_end;
}
/* If this is a recursive query, check that there is no ORDER BY or
** LIMIT clause. Neither of these are supported. */
assert( p->pOffset==0 || p->pLimit );
if( p->pRecurse && (p->pOrderBy || p->pLimit) ){
sqlite3ErrorMsg(pParse, "%s in a recursive query is not allowed",
p->pOrderBy ? "ORDER BY" : "LIMIT"
);
goto multi_select_end;
}
/* Compound SELECTs that have an ORDER BY clause are handled separately.
*/
if( p->pOrderBy ){
return multiSelectOrderBy(pParse, p, pDest);
}
#ifndef SQLITE_OMIT_CTE
if( p->pRecurse ){
int nCol = p->pEList->nExpr;
int addrNext;
int addrSwap;
int iCont, iBreak;
int tmp1, tmp2; /* Cursors used to access temporary tables */
int tmp3 = 0; /* To ensure unique results if UNION */
int eDest = SRT_Table;
SelectDest tmp2dest;
iBreak = sqlite3VdbeMakeLabel(v);
iCont = sqlite3VdbeMakeLabel(v);
tmp1 = pParse->nTab++;
tmp2 = pParse->nTab++;
if( p->op==TK_UNION ){
eDest = SRT_DistTable;
tmp3 = pParse->nTab++;
}
sqlite3SelectDestInit(&tmp2dest, eDest, tmp2);
sqlite3VdbeAddOp2(v, OP_OpenEphemeral, tmp1, nCol);
sqlite3VdbeAddOp2(v, OP_OpenEphemeral, tmp2, nCol);
if( tmp3 ){
p->addrOpenEphm[0] = sqlite3VdbeAddOp2(v, OP_OpenEphemeral, tmp3, 0);
p->selFlags |= SF_UsesEphemeral;
}
/* Store the results of the initial SELECT in tmp2. */
rc = sqlite3Select(pParse, pPrior, &tmp2dest);
if( rc ) goto multi_select_end;
/* Clear tmp1. Then switch the contents of tmp1 and tmp2. Then teturn
** the contents of tmp1 to the caller. Or, if tmp1 is empty at this
** point, the recursive query has finished - jump to address iBreak. */
addrSwap = sqlite3VdbeAddOp2(v, OP_SwapCursors, tmp1, tmp2);
sqlite3VdbeAddOp2(v, OP_Rewind, tmp1, iBreak);
addrNext = sqlite3VdbeCurrentAddr(v);
selectInnerLoop(pParse, p, p->pEList, tmp1, p->pEList->nExpr,
0, 0, &dest, iCont, iBreak);
sqlite3VdbeResolveLabel(v, iCont);
sqlite3VdbeAddOp2(v, OP_Next, tmp1, addrNext);
/* Execute the recursive SELECT. Store the results in tmp2. While this
** SELECT is running, the contents of tmp1 are read by recursive
** references to the current CTE. */
p->pPrior = 0;
p->pRecurse->tnum = tmp1;
p->pRecurse->tabFlags |= TF_Recursive;
rc = sqlite3Select(pParse, p, &tmp2dest);
p->pRecurse->tabFlags &= ~TF_Recursive;
p->pPrior = pPrior;
if( rc ) goto multi_select_end;
sqlite3VdbeAddOp2(v, OP_Goto, 0, addrSwap);
sqlite3VdbeResolveLabel(v, iBreak);
}else
#endif
/* Generate code for the left and right SELECT statements.
*/
switch( p->op ){
@@ -3449,6 +3534,73 @@ static void ctePop(Parse *pParse, struct Cte *pCte){
}
}
static int withExpand(
Walker *pWalker,
struct SrcList_item *pFrom,
struct Cte *pCte
){
Table *pTab;
Parse *pParse = pWalker->pParse;
sqlite3 *db = pParse->db;
assert( pFrom->pSelect==0 );
assert( pFrom->pTab==0 );
if( pCte==pParse->pCte && (pTab = pCte->pTab) ){
/* This is the recursive part of a recursive CTE */
pFrom->pTab = pTab;
pTab->nRef++;
}else{
ExprList *pEList;
Select *pSel;
int bRecursive;
pFrom->pTab = pTab = sqlite3DbMallocZero(db, sizeof(Table));
if( pTab==0 ) return WRC_Abort;
pTab->nRef = 1;
pTab->zName = sqlite3MPrintf(db, "sqlite_sq_%p", (void*)pTab);
pTab->iPKey = -1;
pTab->nRowEst = 1048576;
pTab->tabFlags |= TF_Ephemeral;
pFrom->pSelect = sqlite3SelectDup(db, pCte->pSelect, 0);
if( db->mallocFailed ) return SQLITE_NOMEM;
assert( pFrom->pSelect );
if( ctePush(pParse, pCte) ) return WRC_Abort;
pSel = pFrom->pSelect;
bRecursive = (pSel->op==TK_ALL || pSel->op==TK_UNION);
if( bRecursive ){
assert( pSel->pPrior );
sqlite3WalkSelect(pWalker, pSel->pPrior);
}else{
sqlite3WalkSelect(pWalker, pSel);
}
if( pCte->pCols ){
pEList = pCte->pCols;
}else{
Select *pLeft;
for(pLeft=pSel; pLeft->pPrior; pLeft=pLeft->pPrior);
pEList = pLeft->pEList;
}
selectColumnsFromExprList(pParse, pEList, &pTab->nCol, &pTab->aCol);
if( bRecursive ){
int nRef = pTab->nRef;
pCte->pTab = pTab;
sqlite3WalkSelect(pWalker, pSel);
pCte->pTab = 0;
if( pTab->nRef > nRef){
pSel->pRecurse = pTab;
assert( pTab->tnum==0 );
}
}
ctePop(pParse, pCte);
}
return SQLITE_OK;
}
/*
** This routine is a Walker callback for "expanding" a SELECT statement.
@@ -3515,31 +3667,22 @@ static int selectExpander(Walker *pWalker, Select *p){
#ifndef SQLITE_OMIT_CTE
pCte = searchWith(pParse, pFrom);
if( pCte ){
pFrom->pSelect = sqlite3SelectDup(db, pCte->pSelect, 0);
if( pFrom->pSelect==0 ) return WRC_Abort;
}
if( withExpand(pWalker, pFrom, pCte) ) return WRC_Abort;
}else
#endif
if( pFrom->zName==0 || pCte ){
if( pFrom->zName==0 ){
#ifndef SQLITE_OMIT_SUBQUERY
ExprList *pEList;
Select *pSel = pFrom->pSelect;
/* A sub-query in the FROM clause of a SELECT */
assert( pSel!=0 );
assert( pFrom->pTab==0 );
if( ctePush(pParse, pCte) ) return WRC_Abort;
sqlite3WalkSelect(pWalker, pSel);
ctePop(pParse, pCte);
pFrom->pTab = pTab = sqlite3DbMallocZero(db, sizeof(Table));
if( pTab==0 ) return WRC_Abort;
pTab->nRef = 1;
pTab->zName = sqlite3MPrintf(db, "sqlite_sq_%p", (void*)pTab);
while( pSel->pPrior ){ pSel = pSel->pPrior; }
if( pCte && pCte->pCols ){
pEList = pCte->pCols;
}else{
pEList = pSel->pEList;
}
selectColumnsFromExprList(pParse, pEList, &pTab->nCol, &pTab->aCol);
selectColumnsFromExprList(pParse, pSel->pEList, &pTab->nCol, &pTab->aCol);
pTab->iPKey = -1;
pTab->nRowEst = 1048576;
pTab->tabFlags |= TF_Ephemeral;
@@ -3831,9 +3974,10 @@ static int selectAddSubqueryTypeInfo(Walker *pWalker, Select *p){
if( ALWAYS(pTab!=0) && (pTab->tabFlags & TF_Ephemeral)!=0 ){
/* A sub-query in the FROM clause of a SELECT */
Select *pSel = pFrom->pSelect;
assert( pSel );
while( pSel->pPrior ) pSel = pSel->pPrior;
selectAddColumnTypeAndCollation(pParse, pTab, pSel);
if( pSel ){
while( pSel->pPrior ) pSel = pSel->pPrior;
selectAddColumnTypeAndCollation(pParse, pTab, pSel);
}
}
}
}