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Overview
| Comment: | Simplification of the WHERE loop code generator for NULLS LAST saves a few CPU cycles and about a hundred bytes of code space. |
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| Downloads: | Tarball | ZIP archive | SQL archive |
| Timelines: | family | ancestors | descendants | both | nulls-last |
| Files: | files | file ages | folders |
| SHA3-256: |
e3ed2f496f51234a8f81d90d47ba603b |
| User & Date: | drh 2019-08-23 16:12:20 |
Context
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2019-08-23
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| 17:00 | Additional simplifications of the WHERE loop code generator logic for NULLS LAST. (check-in: 1383680d user: drh tags: nulls-last) | |
| 16:12 | Simplification of the WHERE loop code generator for NULLS LAST saves a few CPU cycles and about a hundred bytes of code space. (check-in: e3ed2f49 user: drh tags: nulls-last) | |
| 13:32 | Invert the meaning of the regBignull flag so that it is 1 when doing the normal scan and 1 when scanning nulls. This enables the re-do jump at the bottom of the loop to be coded with a single OP_IfNotZero opcode, rather than a sequence of OP_If, OP_Integer, OP_Goto. (check-in: bf875e1a user: drh tags: nulls-last) | |
Changes
Changes to src/wherecode.c.
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if( sqlite3ExprIsVector(pRight)==0 ){
disableTerm(pLevel, pRangeStart);
}else{
startEq = 1;
}
bSeekPastNull = 0;
}else if( bSeekPastNull ){
sqlite3VdbeAddOp2(v, OP_Null, 0, regBase+nEq);
nConstraint++;
startEq = 0;
start_constraints = 1;
}else if( regBignull ){
sqlite3VdbeAddOp2(v, OP_Null, 0, regBase+nEq);
start_constraints = 1;
nConstraint++;
}
codeApplyAffinity(pParse, regBase, nConstraint - bSeekPastNull, zStartAff);
if( pLoop->nSkip>0 && nConstraint==pLoop->nSkip ){
................................................................................
VdbeCoverageIf(v, op==OP_Rewind); testcase( op==OP_Rewind );
VdbeCoverageIf(v, op==OP_Last); testcase( op==OP_Last );
VdbeCoverageIf(v, op==OP_SeekGT); testcase( op==OP_SeekGT );
VdbeCoverageIf(v, op==OP_SeekGE); testcase( op==OP_SeekGE );
VdbeCoverageIf(v, op==OP_SeekLE); testcase( op==OP_SeekLE );
VdbeCoverageIf(v, op==OP_SeekLT); testcase( op==OP_SeekLT );
if( regBignull ){
sqlite3VdbeAddOp2(v, OP_Goto, 0, sqlite3VdbeCurrentAddr(v)+2);
if( bStopAtNull ){
start_constraints = (nConstraint>1);
op = aStartOp[(start_constraints<<2) + (startEq<<1) + bRev];
sqlite3VdbeAddOp4Int(v, op, iIdxCur, addrNxt, regBase, nConstraint-1);
VdbeCoverage(v);
VdbeCoverageIf(v, op==OP_Rewind); testcase( op==OP_Rewind );
VdbeCoverageIf(v, op==OP_Last); testcase( op==OP_Last );
VdbeCoverageIf(v, op==OP_SeekGT); testcase( op==OP_SeekGT );
VdbeCoverageIf(v, op==OP_SeekGE); testcase( op==OP_SeekGE );
VdbeCoverageIf(v, op==OP_SeekLE); testcase( op==OP_SeekLE );
VdbeCoverageIf(v, op==OP_SeekLT); testcase( op==OP_SeekLT );
}else{
op = aStartOp[(start_constraints<<2) + ((!startEq)<<1) + bRev];
sqlite3VdbeAddOp4Int(v, op, iIdxCur, addrNxt, regBase, nConstraint);
VdbeCoverage(v);
VdbeCoverageIf(v, op==OP_Rewind); testcase( op==OP_Rewind );
VdbeCoverageIf(v, op==OP_Last); testcase( op==OP_Last );
VdbeCoverageIf(v, op==OP_SeekGT); testcase( op==OP_SeekGT );
VdbeCoverageIf(v, op==OP_SeekGE); testcase( op==OP_SeekGE );
VdbeCoverageIf(v, op==OP_SeekLE); testcase( op==OP_SeekLE );
VdbeCoverageIf(v, op==OP_SeekLT); testcase( op==OP_SeekLT );
}
}
}
/* Load the value for the inequality constraint at the end of the
** range (if any).
*/
nConstraint = nEq;
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if( sqlite3ExprIsVector(pRight)==0 ){
disableTerm(pLevel, pRangeStart);
}else{
startEq = 1;
}
bSeekPastNull = 0;
}else if( bSeekPastNull ){
startEq = 0;
sqlite3VdbeAddOp2(v, OP_Null, 0, regBase+nEq);
start_constraints = 1;
nConstraint++;
}else if( regBignull ){
sqlite3VdbeAddOp2(v, OP_Null, 0, regBase+nEq);
start_constraints = 1;
nConstraint++;
}
codeApplyAffinity(pParse, regBase, nConstraint - bSeekPastNull, zStartAff);
if( pLoop->nSkip>0 && nConstraint==pLoop->nSkip ){
................................................................................
VdbeCoverageIf(v, op==OP_Rewind); testcase( op==OP_Rewind );
VdbeCoverageIf(v, op==OP_Last); testcase( op==OP_Last );
VdbeCoverageIf(v, op==OP_SeekGT); testcase( op==OP_SeekGT );
VdbeCoverageIf(v, op==OP_SeekGE); testcase( op==OP_SeekGE );
VdbeCoverageIf(v, op==OP_SeekLE); testcase( op==OP_SeekLE );
VdbeCoverageIf(v, op==OP_SeekLT); testcase( op==OP_SeekLT );
assert( bSeekPastNull==0 || bStopAtNull==0 );
if( regBignull ){
assert( bSeekPastNull==1 || bStopAtNull==1 );
assert( bStopAtNull==startEq );
sqlite3VdbeAddOp2(v, OP_Goto, 0, sqlite3VdbeCurrentAddr(v)+2);
op = aStartOp[(nConstraint>1)*4 + 2 + bRev];
sqlite3VdbeAddOp4Int(v, op, iIdxCur, addrNxt, regBase,
nConstraint-startEq);
VdbeCoverage(v);
VdbeCoverageIf(v, op==OP_Rewind); testcase( op==OP_Rewind );
VdbeCoverageIf(v, op==OP_Last); testcase( op==OP_Last );
VdbeCoverageIf(v, op==OP_SeekGE); testcase( op==OP_SeekGE );
VdbeCoverageIf(v, op==OP_SeekLE); testcase( op==OP_SeekLE );
assert( op==OP_Rewind || op==OP_Last || op==OP_SeekGE || op==OP_SeekLE);
}
}
/* Load the value for the inequality constraint at the end of the
** range (if any).
*/
nConstraint = nEq;
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