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Overview
| Comment: | Improvement on the previous check-in: disallow automatic indexes for any loop that is expected to run less than twice. |
|---|---|
| Downloads: | Tarball | ZIP archive | SQL archive |
| Timelines: | family | ancestors | descendants | both | planner-improvements |
| Files: | files | file ages | folders |
| SHA1: |
aab53a21894ba51d325fd8f8f4bb4163 |
| User & Date: | drh 2016-02-25 18:22:09 |
Context
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2016-02-25
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| 18:40 | Query planner improvements: Take the LIMIT into account when estimated the cost of an ORDER BY. Avoid automatic indexes on query loops that are expected to run less than twice. See [9e2b2681] for a later enhancement. check-in: bf46179d user: drh tags: trunk | |
| 18:22 | Improvement on the previous check-in: disallow automatic indexes for any loop that is expected to run less than twice. Closed-Leaf check-in: aab53a21 user: drh tags: planner-improvements | |
| 18:03 | Do not use an automatic index on an outer loop that only runs once. check-in: 5957e793 user: drh tags: planner-improvements | |
Changes
Changes to src/where.c.
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LogEst rUnsorted; /* Unsorted cost of (pFrom+pWLoop) */
i8 isOrdered = pFrom->isOrdered; /* isOrdered for (pFrom+pWLoop) */
Bitmask maskNew; /* Mask of src visited by (..) */
Bitmask revMask = 0; /* Mask of rev-order loops for (..) */
if( (pWLoop->prereq & ~pFrom->maskLoop)!=0 ) continue;
if( (pWLoop->maskSelf & pFrom->maskLoop)!=0 ) continue;
if( iLoop==0
&& (pWLoop->wsFlags & WHERE_AUTO_INDEX)!=0
&& pParse->nQueryLoop==0
){
/* Never put an automatic index in the outer loop if the query
** is only being run once. */
continue;
}
/* At this point, pWLoop is a candidate to be the next loop.
** Compute its cost */
rUnsorted = sqlite3LogEstAdd(pWLoop->rSetup,pWLoop->rRun + pFrom->nRow);
rUnsorted = sqlite3LogEstAdd(rUnsorted, pFrom->rUnsorted);
nOut = pFrom->nRow + pWLoop->nOut;
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3581 3582 3583 3584 3585 3586 3587 3588 3589 3590 3591 3592 3593 3594 3595 3596 3597 3598 |
LogEst rUnsorted; /* Unsorted cost of (pFrom+pWLoop) */
i8 isOrdered = pFrom->isOrdered; /* isOrdered for (pFrom+pWLoop) */
Bitmask maskNew; /* Mask of src visited by (..) */
Bitmask revMask = 0; /* Mask of rev-order loops for (..) */
if( (pWLoop->prereq & ~pFrom->maskLoop)!=0 ) continue;
if( (pWLoop->maskSelf & pFrom->maskLoop)!=0 ) continue;
if( (pWLoop->wsFlags & WHERE_AUTO_INDEX)!=0 && pFrom->nRow<10 ){
/* Do not use an automatic index if the this loop is expected
** to run less than 2 times. */
assert( 10==sqlite3LogEst(2) );
continue;
}
/* At this point, pWLoop is a candidate to be the next loop.
** Compute its cost */
rUnsorted = sqlite3LogEstAdd(pWLoop->rSetup,pWLoop->rRun + pFrom->nRow);
rUnsorted = sqlite3LogEstAdd(rUnsorted, pFrom->rUnsorted);
nOut = pFrom->nRow + pWLoop->nOut;
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