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For the OP_SeekScan opcode, adjust the number of steps run before giving

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up based on the estimated number of comparisons needed to perform a seek.

FossilOrigin-Name: dc4172e6b8e1f62dc7329a3adb2223f290bc4c8055c265e88182ef432f4bcf10
This commit is contained in:
drh
2020-09-30 18:03:22 +00:00
parent a957e22fa4
commit 4f65b3bbfb
3 changed files with 17 additions and 8 deletions
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11
src/wherecode.c
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@@ -1807,7 +1807,16 @@ Bitmask sqlite3WhereCodeOneLoopStart(
if( (pLoop->wsFlags & WHERE_IN_SEEKSCAN)!=0 ){
assert( op==OP_SeekGE );
assert( regBignull==0 );
sqlite3VdbeAddOp1(v, OP_SeekScan, 10); VdbeCoverage(v);
/* TUNING: The OP_SeekScan opcode seeks to reduce the number
** of expensive seek operations by replacing a single seek with
** 1 or more step operations. The question is, how many steps
** should we try before giving up and going with a seek. The cost
** of a seek is proportional to the logarithm of the of the number
** of entries in the tree, so basing the number of steps to try
** on the estimated number of rows in the btree seems like a good
** guess. */
sqlite3VdbeAddOp1(v, OP_SeekScan, (pIdx->aiRowLogEst[0]+9)/10);
VdbeCoverage(v);
}
sqlite3VdbeAddOp4Int(v, op, iIdxCur, addrNxt, regBase, nConstraint);
VdbeCoverage(v);