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When processing an "ORDER BY ... LIMIT" that does not use an index, check

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whether or not a record may appear in the final result set before adding it to
the sorter.

FossilOrigin-Name: 71bf91c218334381b1b4bdba6a093e623b62e17f3e8550e154a11f0cb0b404f3
This commit is contained in:
dan
2018-04-26 16:13:47 +00:00
parent de7ca50dac
commit f226f03d4f
3 changed files with 41 additions and 37 deletions
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59
src/select.c
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@@ -579,7 +579,6 @@ static void pushOntoSorter(
if( nPrefixReg==0 && nData>0 ){
sqlite3ExprCodeMove(pParse, regData, regBase+nExpr+bSeq, nData);
}
sqlite3VdbeAddOp3(v, OP_MakeRecord, regBase+nOBSat, nBase-nOBSat, regRecord);
if( nOBSat>0 ){
int regPrevKey; /* The first nOBSat columns of the previous row */
int addrFirst; /* Address of the OP_IfNot opcode */
@@ -588,6 +587,7 @@ static void pushOntoSorter(
int nKey; /* Number of sorting key columns, including OP_Sequence */
KeyInfo *pKI; /* Original KeyInfo on the sorter table */
sqlite3VdbeAddOp3(v, OP_MakeRecord, regBase+nOBSat, nBase-nOBSat,regRecord);
regPrevKey = pParse->nMem+1;
pParse->nMem += pSort->nOBSat;
nKey = nExpr - pSort->nOBSat + bSeq;
@@ -621,6 +621,35 @@ static void pushOntoSorter(
sqlite3ExprCodeMove(pParse, regBase, regPrevKey, pSort->nOBSat);
sqlite3VdbeJumpHere(v, addrJmp);
}
if( iLimit ){
/* At this point the values for the new sorter entry are stored
** in an array of registers. They need to be composed into a record
** and inserted into the sorter if either (a) there are currently
** less than LIMIT+OFFSET items or (b) the new record is smaller than
** the largest record currently in the sorter. If (b) is true and there
** are already LIMIT+OFFSET items in the sorter, delete the largest
** entry before inserting the new one. This way there are never more
** than LIMIT+OFFSET items in the sorter.
**
** If the new record does not need to be inserted into the sorter,
** jump to the next iteration of the loop. Or, if the
** pSort->bOrderedInnerLoop flag is set to indicate that the inner
** loop delivers items in sorted order, jump to the next iteration
** of the outer loop.
*/
int iCsr = pSort->iECursor;
int iJmp = sqlite3VdbeCurrentAddr(v)+5+(nOBSat<=0)+pSort->bOrderedInnerLoop;
assert( pSort->bOrderedInnerLoop==0 || pSort->bOrderedInnerLoop==1 );
sqlite3VdbeAddOp2(v, OP_IfNotZero, iLimit, sqlite3VdbeCurrentAddr(v)+4);
VdbeCoverage(v);
sqlite3VdbeAddOp2(v, OP_Last, iCsr, 0);
sqlite3VdbeAddOp4Int(v, OP_IdxLE, iCsr, iJmp, regBase+nOBSat, nExpr-nOBSat);
VdbeCoverage(v);
sqlite3VdbeAddOp1(v, OP_Delete, iCsr);
}
if( nOBSat<=0 ){
sqlite3VdbeAddOp3(v, OP_MakeRecord, regBase+nOBSat, nBase-nOBSat,regRecord);
}
if( pSort->sortFlags & SORTFLAG_UseSorter ){
op = OP_SorterInsert;
}else{
@@ -628,34 +657,6 @@ static void pushOntoSorter(
}
sqlite3VdbeAddOp4Int(v, op, pSort->iECursor, regRecord,
regBase+nOBSat, nBase-nOBSat);
if( iLimit ){
int addr;
int r1 = 0;
/* Fill the sorter until it contains LIMIT+OFFSET entries. (The iLimit
** register is initialized with value of LIMIT+OFFSET.) After the sorter
** fills up, delete the least entry in the sorter after each insert.
** Thus we never hold more than the LIMIT+OFFSET rows in memory at once */
addr = sqlite3VdbeAddOp1(v, OP_IfNotZero, iLimit); VdbeCoverage(v);
sqlite3VdbeAddOp1(v, OP_Last, pSort->iECursor);
if( pSort->bOrderedInnerLoop ){
r1 = ++pParse->nMem;
sqlite3VdbeAddOp3(v, OP_Column, pSort->iECursor, nExpr, r1);
VdbeComment((v, "seq"));
}
sqlite3VdbeAddOp1(v, OP_Delete, pSort->iECursor);
if( pSort->bOrderedInnerLoop ){
/* If the inner loop is driven by an index such that values from
** the same iteration of the inner loop are in sorted order, then
** immediately jump to the next iteration of an inner loop if the
** entry from the current iteration does not fit into the top
** LIMIT+OFFSET entries of the sorter. */
int iBrk = sqlite3VdbeCurrentAddr(v) + 2;
sqlite3VdbeAddOp3(v, OP_Eq, regBase+nExpr, iBrk, r1);
sqlite3VdbeChangeP5(v, SQLITE_NULLEQ);
VdbeCoverage(v);
}
sqlite3VdbeJumpHere(v, addr);
}
}
/*