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Revisiting the IN-scan optimization to try to fix it for the corner case

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where the statistics deceive the query planner into using a scan when
an indexed lookup would be better.  This check-in changes the code
generation to do the IN-scan using a new OP_SeekScan opcode.  That new
opcode is designed to abandon the scan and fall back to a seek if
it doesn't find a match quickly enough.  For this work-in-progress check-in, 
OP_SeekScan is still a no-op and OP_SeekGE still ends up doing all the work.

FossilOrigin-Name: d720b6981eeb0ffdb14494ca63eca298ee724ae4ad4863c7c7cbfdad7fa52519
This commit is contained in:
drh
2020-09-28 19:51:54 +00:00
parent 75fa266341
commit 68cf0ace3d
6 changed files with 74 additions and 11 deletions
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5
src/wherecode.c
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@@ -1804,6 +1804,11 @@ Bitmask sqlite3WhereCodeOneLoopStart(
op = aStartOp[(start_constraints<<2) + (startEq<<1) + bRev];
assert( op!=0 );
if( (pLoop->wsFlags & WHERE_IN_SEEKSCAN)!=0 ){
assert( op==OP_SeekGE );
assert( regBignull==0 );
sqlite3VdbeAddOp1(v, OP_SeekScan, 10);
}
sqlite3VdbeAddOp4Int(v, op, iIdxCur, addrNxt, regBase, nConstraint);
VdbeCoverage(v);
VdbeCoverageIf(v, op==OP_Rewind); testcase( op==OP_Rewind );