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Overview
| Comment: | Additional simplifications of the WHERE loop code generator logic for NULLS LAST. |
|---|---|
| Downloads: | Tarball | ZIP archive | SQL archive |
| Timelines: | family | ancestors | descendants | both | nulls-last |
| Files: | files | file ages | folders |
| SHA3-256: |
1383680d927d7d703933be7653c00191 |
| User & Date: | drh 2019-08-23 17:00:22 |
Context
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2019-08-23
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| 17:09 | Revise the VDBE comments for NULL-scan so that they also work make sense when reading a NULLS FIRST plan. (check-in: bfe79378 user: drh tags: nulls-last) | |
| 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) | |
Changes
Changes to src/wherecode.c.
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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 );
................................................................................
/* Top of the loop body */
pLevel->p2 = sqlite3VdbeCurrentAddr(v);
/* Check if the index cursor is past the end of the range. */
if( nConstraint ){
if( regBignull ){
sqlite3VdbeAddOp2(v, OP_IfNot, regBignull, sqlite3VdbeCurrentAddr(v)+3);
VdbeComment((v, "If NULL-scan active"));
VdbeCoverage(v);
}
op = aEndOp[bRev*2 + endEq];
sqlite3VdbeAddOp4Int(v, op, iIdxCur, addrNxt, regBase, nConstraint);
testcase( op==OP_IdxGT ); VdbeCoverageIf(v, op==OP_IdxGT );
testcase( op==OP_IdxGE ); VdbeCoverageIf(v, op==OP_IdxGE );
testcase( op==OP_IdxLT ); VdbeCoverageIf(v, op==OP_IdxLT );
testcase( op==OP_IdxLE ); VdbeCoverageIf(v, op==OP_IdxLE );
}
if( regBignull ){
sqlite3VdbeAddOp2(v, OP_If, regBignull, sqlite3VdbeCurrentAddr(v)+2);
VdbeComment((v, "If NULL-scan pending"));
VdbeCoverage(v);
if( bStopAtNull ){
op = aEndOp[bRev*2 + 0];
assert( op==OP_IdxGE || op==OP_IdxLE );
sqlite3VdbeAddOp4Int(v, op, iIdxCur, addrNxt, regBase, nConstraint);
testcase( op==OP_IdxGE ); VdbeCoverageIf(v, op==OP_IdxGE );
testcase( op==OP_IdxLE ); VdbeCoverageIf(v, op==OP_IdxLE );
}else{
op = aEndOp[bRev*2 + endEq];
sqlite3VdbeAddOp4Int(v, op, iIdxCur, addrNxt, regBase, nConstraint+1);
testcase( op==OP_IdxGT ); VdbeCoverageIf(v, op==OP_IdxGT );
testcase( op==OP_IdxGE ); VdbeCoverageIf(v, op==OP_IdxGE );
testcase( op==OP_IdxLT ); VdbeCoverageIf(v, op==OP_IdxLT );
testcase( op==OP_IdxLE ); VdbeCoverageIf(v, op==OP_IdxLE );
}
}
if( pLoop->wsFlags & WHERE_IN_EARLYOUT ){
sqlite3VdbeAddOp2(v, OP_SeekHit, iIdxCur, 1);
}
/* Seek the table cursor, if required */
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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( bSeekPastNull==!bStopAtNull );
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 );
................................................................................
/* Top of the loop body */
pLevel->p2 = sqlite3VdbeCurrentAddr(v);
/* Check if the index cursor is past the end of the range. */
if( nConstraint ){
if( regBignull ){
/* Except, skip the end-of-range check while doing the NULL-scan */
sqlite3VdbeAddOp2(v, OP_IfNot, regBignull, sqlite3VdbeCurrentAddr(v)+3);
VdbeComment((v, "If NULL-scan active"));
VdbeCoverage(v);
}
op = aEndOp[bRev*2 + endEq];
sqlite3VdbeAddOp4Int(v, op, iIdxCur, addrNxt, regBase, nConstraint);
testcase( op==OP_IdxGT ); VdbeCoverageIf(v, op==OP_IdxGT );
testcase( op==OP_IdxGE ); VdbeCoverageIf(v, op==OP_IdxGE );
testcase( op==OP_IdxLT ); VdbeCoverageIf(v, op==OP_IdxLT );
testcase( op==OP_IdxLE ); VdbeCoverageIf(v, op==OP_IdxLE );
}
if( regBignull ){
/* During a NULL-scan, check to see if we have reached the end of
** the NULLs */
assert( bSeekPastNull==!bStopAtNull );
assert( bSeekPastNull+bStopAtNull==1 );
assert( nConstraint+bSeekPastNull>0 );
sqlite3VdbeAddOp2(v, OP_If, regBignull, sqlite3VdbeCurrentAddr(v)+2);
VdbeComment((v, "If NULL-scan pending"));
VdbeCoverage(v);
op = aEndOp[bRev*2 + bSeekPastNull];
sqlite3VdbeAddOp4Int(v, op, iIdxCur, addrNxt, regBase,
nConstraint+bSeekPastNull);
testcase( op==OP_IdxGT ); VdbeCoverageIf(v, op==OP_IdxGT );
testcase( op==OP_IdxGE ); VdbeCoverageIf(v, op==OP_IdxGE );
testcase( op==OP_IdxLT ); VdbeCoverageIf(v, op==OP_IdxLT );
testcase( op==OP_IdxLE ); VdbeCoverageIf(v, op==OP_IdxLE );
}
if( pLoop->wsFlags & WHERE_IN_EARLYOUT ){
sqlite3VdbeAddOp2(v, OP_SeekHit, iIdxCur, 1);
}
/* Seek the table cursor, if required */
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