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Add support for LIMIT and OFFSET in a recursive query.

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FossilOrigin-Name: 1945484e6b9769c1943f750f5b09860417fb190a
This commit is contained in:
drh
2014-01-22 18:07:04 +00:00
parent fe1c6bb9c2
commit aa9ce7078a
4 changed files with 54 additions and 34 deletions
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55
src/select.c
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@@ -462,13 +462,13 @@ static void pushOntoSorter(
*/
static void codeOffset(
Vdbe *v, /* Generate code into this VM */
Select *p, /* The SELECT statement being coded */
int iOffset, /* Register holding the offset counter */
int iContinue /* Jump here to skip the current record */
){
if( p->iOffset && iContinue!=0 ){
if( iOffset>0 && iContinue!=0 ){
int addr;
sqlite3VdbeAddOp2(v, OP_AddImm, p->iOffset, -1);
addr = sqlite3VdbeAddOp1(v, OP_IfNeg, p->iOffset);
sqlite3VdbeAddOp2(v, OP_AddImm, iOffset, -1);
addr = sqlite3VdbeAddOp1(v, OP_IfNeg, iOffset);
sqlite3VdbeAddOp2(v, OP_Goto, 0, iContinue);
VdbeComment((v, "skip OFFSET records"));
sqlite3VdbeJumpHere(v, addr);
@@ -571,7 +571,7 @@ static void selectInnerLoop(
assert( pEList!=0 );
hasDistinct = pDistinct ? pDistinct->eTnctType : WHERE_DISTINCT_NOOP;
if( pOrderBy==0 && !hasDistinct ){
codeOffset(v, p, iContinue);
codeOffset(v, p->iOffset, iContinue);
}
/* Pull the requested columns.
@@ -653,7 +653,7 @@ static void selectInnerLoop(
}
}
if( pOrderBy==0 ){
codeOffset(v, p, iContinue);
codeOffset(v, p->iOffset, iContinue);
}
}
@@ -1069,13 +1069,13 @@ static void generateSortTail(
int ptab2 = pParse->nTab++;
sqlite3VdbeAddOp3(v, OP_OpenPseudo, ptab2, regSortOut, pOrderBy->nExpr+2);
addr = 1 + sqlite3VdbeAddOp2(v, OP_SorterSort, iTab, addrBreak);
codeOffset(v, p, addrContinue);
codeOffset(v, p->iOffset, addrContinue);
sqlite3VdbeAddOp2(v, OP_SorterData, iTab, regSortOut);
sqlite3VdbeAddOp3(v, OP_Column, ptab2, pOrderBy->nExpr+1, regRow);
sqlite3VdbeChangeP5(v, OPFLAG_CLEARCACHE);
}else{
addr = 1 + sqlite3VdbeAddOp2(v, OP_Sort, iTab, addrBreak);
codeOffset(v, p, addrContinue);
codeOffset(v, p->iOffset, addrContinue);
sqlite3VdbeAddOp3(v, OP_Column, iTab, pOrderBy->nExpr+1, regRow);
}
switch( eDest ){
@@ -1639,8 +1639,13 @@ Vdbe *sqlite3GetVdbe(Parse *pParse){
**
** This routine changes the values of iLimit and iOffset only if
** a limit or offset is defined by pLimit and pOffset. iLimit and
** iOffset should have been preset to appropriate default values
** (usually but not always -1) prior to calling this routine.
** iOffset should have been preset to appropriate default values (zero)
** prior to calling this routine.
**
** The iOffset register (if it exists) is initialized to the value
** of the OFFSET. The iLimit register is initialized to LIMIT. Register
** iOffset+1 is initialized to LIMIT+OFFSET.
**
** Only if pLimit!=0 or pOffset!=0 do the limit registers get
** redefined. The UNION ALL operator uses this property to force
** the reuse of the same limit and offset registers across multiple
@@ -1664,7 +1669,7 @@ static void computeLimitRegisters(Parse *pParse, Select *p, int iBreak){
if( p->pLimit ){
p->iLimit = iLimit = ++pParse->nMem;
v = sqlite3GetVdbe(pParse);
if( NEVER(v==0) ) return; /* VDBE should have already been allocated */
assert( v!=0 );
if( sqlite3ExprIsInteger(p->pLimit, &n) ){
sqlite3VdbeAddOp2(v, OP_Integer, n, iLimit);
VdbeComment((v, "LIMIT counter"));
@@ -1778,21 +1783,21 @@ static void generateWithRecursiveQuery(
int i; /* Loop counter */
int rc; /* Result code */
ExprList *pOrderBy; /* The ORDER BY clause */
Expr *pLimit, *pOffset; /* Saved LIMIT and OFFSET */
int regLimit, regOffset; /* Registers used by LIMIT and OFFSET */
/* Obtain authorization to do a recursive query */
if( sqlite3AuthCheck(pParse, SQLITE_RECURSIVE, 0, 0, 0) ) return;
addrBreak = sqlite3VdbeMakeLabel(v);
/* Check that there is no ORDER BY or LIMIT clause. Neither of these
** are currently supported on recursive queries.
*/
assert( p->pOffset==0 || p->pLimit );
if( /*p->pOrderBy ||*/ p->pLimit ){
sqlite3ErrorMsg(pParse, "%s in a recursive query",
p->pOrderBy ? "ORDER BY" : "LIMIT"
);
return;
}
/* Process the LIMIT and OFFSET clauses, if they exist */
addrBreak = sqlite3VdbeMakeLabel(v);
computeLimitRegisters(pParse, p, addrBreak);
pLimit = p->pLimit;
pOffset = p->pOffset;
regLimit = p->iLimit;
regOffset = p->iOffset;
p->pLimit = p->pOffset = 0;
p->iLimit = p->iOffset = 0;
/* Locate the cursor number of the Current table */
for(i=0; ALWAYS(i<pSrc->nSrc); i++){
@@ -1853,8 +1858,10 @@ static void generateWithRecursiveQuery(
/* Output the single row in Current */
addrCont = sqlite3VdbeMakeLabel(v);
codeOffset(v, regOffset, addrCont);
selectInnerLoop(pParse, p, p->pEList, iCurrent,
0, 0, pDest, addrCont, addrBreak);
if( regLimit ) sqlite3VdbeAddOp3(v, OP_IfZero, regLimit, addrBreak, -1);
sqlite3VdbeResolveLabel(v, addrCont);
/* Execute the recursive SELECT taking the single row in Current as
@@ -1871,6 +1878,8 @@ static void generateWithRecursiveQuery(
end_of_recursive_query:
p->pOrderBy = pOrderBy;
p->pLimit = pLimit;
p->pOffset = pOffset;
return;
}
#endif
@@ -2326,7 +2335,7 @@ static int generateOutputSubroutine(
/* Suppress the first OFFSET entries if there is an OFFSET clause
*/
codeOffset(v, p, iContinue);
codeOffset(v, p->iOffset, iContinue);
switch( pDest->eDest ){
/* Store the result as data using a unique key.