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Simplifications to the VDBE bytecode that handles LIMIT and OFFSET.

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FossilOrigin-Name: 041df7c2f14b95868a08090354ebb3308050790e
This commit is contained in:
drh
2015-10-06 21:07:06 +00:00
parent a2507137f3
commit 8b0cf38a12
5 changed files with 47 additions and 52 deletions
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28
src/select.c
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@@ -579,7 +579,7 @@ static void pushOntoSorter(
}else{
iLimit = pSelect->iLimit;
}
addr = sqlite3VdbeAddOp3(v, OP_IfNotZero, iLimit, 0, -1); VdbeCoverage(v);
addr = sqlite3VdbeAddOp3(v, OP_IfNotZero, iLimit, 0, 1); VdbeCoverage(v);
sqlite3VdbeAddOp1(v, OP_Last, pSort->iECursor);
sqlite3VdbeAddOp1(v, OP_Delete, pSort->iECursor);
sqlite3VdbeJumpHere(v, addr);
@@ -595,11 +595,8 @@ static void codeOffset(
int iContinue /* Jump here to skip the current record */
){
if( iOffset>0 ){
int addr;
addr = sqlite3VdbeAddOp3(v, OP_IfNeg, iOffset, 0, -1); VdbeCoverage(v);
sqlite3VdbeGoto(v, iContinue);
VdbeComment((v, "skip OFFSET records"));
sqlite3VdbeJumpHere(v, addr);
sqlite3VdbeAddOp3(v, OP_IfPos, iOffset, iContinue, 1); VdbeCoverage(v);
VdbeComment((v, "OFFSET"));
}
}
@@ -1815,7 +1812,7 @@ static void computeLimitRegisters(Parse *pParse, Select *p, int iBreak){
Vdbe *v = 0;
int iLimit = 0;
int iOffset;
int addr1, n;
int n;
if( p->iLimit ) return;
/*
@@ -1850,14 +1847,10 @@ static void computeLimitRegisters(Parse *pParse, Select *p, int iBreak){
sqlite3ExprCode(pParse, p->pOffset, iOffset);
sqlite3VdbeAddOp1(v, OP_MustBeInt, iOffset); VdbeCoverage(v);
VdbeComment((v, "OFFSET counter"));
addr1 = sqlite3VdbeAddOp1(v, OP_IfPos, iOffset); VdbeCoverage(v);
sqlite3VdbeAddOp2(v, OP_Integer, 0, iOffset);
sqlite3VdbeJumpHere(v, addr1);
sqlite3VdbeAddOp3(v, OP_SetIfNotPos, iOffset, iOffset, 0);
sqlite3VdbeAddOp3(v, OP_Add, iLimit, iOffset, iOffset+1);
VdbeComment((v, "LIMIT+OFFSET"));
addr1 = sqlite3VdbeAddOp1(v, OP_IfPos, iLimit); VdbeCoverage(v);
sqlite3VdbeAddOp2(v, OP_Integer, -1, iOffset+1);
sqlite3VdbeJumpHere(v, addr1);
sqlite3VdbeAddOp3(v, OP_SetIfNotPos, iLimit, iOffset+1, -1);
}
}
}
@@ -2274,14 +2267,9 @@ static int multiSelect(
addr = sqlite3VdbeAddOp1(v, OP_IfNot, p->iLimit); VdbeCoverage(v);
VdbeComment((v, "Jump ahead if LIMIT reached"));
if( p->iOffset ){
int addr2;
sqlite3VdbeAddOp3(v, OP_SetIfNotPos, p->iOffset, p->iOffset, 0);
sqlite3VdbeAddOp3(v, OP_Add, p->iLimit, p->iOffset, p->iOffset+1);
addr2 = sqlite3VdbeAddOp1(v, OP_IfPos, p->iOffset); VdbeCoverage(v);
sqlite3VdbeAddOp2(v, OP_SCopy, p->iLimit, p->iOffset+1);
sqlite3VdbeJumpHere(v, addr2);
addr2 = sqlite3VdbeAddOp1(v, OP_IfPos, p->iLimit); VdbeCoverage(v);
sqlite3VdbeAddOp2(v, OP_Integer, -1, p->iOffset+1);
sqlite3VdbeJumpHere(v, addr2);
sqlite3VdbeAddOp3(v, OP_SetIfNotPos, p->iLimit, p->iOffset+1, -1);
}
}
explainSetInteger(iSub2, pParse->iNextSelectId);