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Change the recursive common table expression algorithm to use a queue instead

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of a pair of tables.  Runs about 25% faster on the sudoku solver query. 
The OP_SwapCursors opcode is no longer required.  The current implementation
uses just a fifo, but the plan is to change it into a queue that will support 
ORDER BY and LIMIT in a recursive query.

FossilOrigin-Name: b2671e1133d2f1fbd36e7cd4b86d6cc7b528aa97
This commit is contained in:
drh
2014-01-21 22:25:45 +00:00
parent 8561c81ed6
commit e73f059093
6 changed files with 76 additions and 86 deletions
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12
src/where.c
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@@ -3410,10 +3410,14 @@ static Bitmask codeOneLoopStart(
static const u8 aStep[] = { OP_Next, OP_Prev };
static const u8 aStart[] = { OP_Rewind, OP_Last };
assert( bRev==0 || bRev==1 );
pLevel->op = aStep[bRev];
pLevel->p1 = iCur;
pLevel->p2 = 1 + sqlite3VdbeAddOp2(v, aStart[bRev], iCur, addrBrk);
pLevel->p5 = SQLITE_STMTSTATUS_FULLSCAN_STEP;
if( pTabItem->isRecursive ){
pLevel->op = OP_Noop;
}else{
pLevel->op = aStep[bRev];
pLevel->p1 = iCur;
pLevel->p2 = 1 + sqlite3VdbeAddOp2(v, aStart[bRev], iCur, addrBrk);
pLevel->p5 = SQLITE_STMTSTATUS_FULLSCAN_STEP;
}
}
/* Insert code to test every subexpression that can be completely