Many hyperlinks are disabled.
Use anonymous login
to enable hyperlinks.
Overview
| Comment: | Add text to the header comment of whereLoopAddBtree() describing how the costs of various b-tree loops are estimated. |
|---|---|
| Downloads: | Tarball | ZIP archive |
| Timelines: | family | ancestors | descendants | both | experimental-costs |
| Files: | files | file ages | folders |
| SHA1: |
05e6e16cb28c9ffb4596bd2ef81f687c |
| User & Date: | dan 2014-04-30 15:00:16.197 |
Context
|
2014-04-30
| ||
| 15:22 | Modify the way the costs of various query plans are estimated. If the user supplies a likelihood() value (or equivalent) on an indexed WHERE constraint, use it to estimate the number of index rows visited. (check-in: 90e3667647 user: dan tags: trunk) | |
| 15:00 | Add text to the header comment of whereLoopAddBtree() describing how the costs of various b-tree loops are estimated. (Closed-Leaf check-in: 05e6e16cb2 user: dan tags: experimental-costs) | |
| 14:53 | Update a couple of test cases to account for the fact that this branch prefers an index scan and partial sort over a full-table scan and full external sort. (check-in: 9b975bf33c user: dan tags: experimental-costs) | |
Changes
Changes to src/where.c.
| ︙ | ︙ | |||
4345 4346 4347 4348 4349 4350 4351 4352 4353 4354 4355 4356 4357 4358 |
return 0;
}
/*
** Add all WhereLoop objects for a single table of the join where the table
** is idenfied by pBuilder->pNew->iTab. That table is guaranteed to be
** a b-tree table, not a virtual table.
*/
static int whereLoopAddBtree(
WhereLoopBuilder *pBuilder, /* WHERE clause information */
Bitmask mExtra /* Extra prerequesites for using this table */
){
WhereInfo *pWInfo; /* WHERE analysis context */
Index *pProbe; /* An index we are evaluating */
| > > > > > > > > > > > > > > > > > > > > > > > | 4345 4346 4347 4348 4349 4350 4351 4352 4353 4354 4355 4356 4357 4358 4359 4360 4361 4362 4363 4364 4365 4366 4367 4368 4369 4370 4371 4372 4373 4374 4375 4376 4377 4378 4379 4380 4381 |
return 0;
}
/*
** Add all WhereLoop objects for a single table of the join where the table
** is idenfied by pBuilder->pNew->iTab. That table is guaranteed to be
** a b-tree table, not a virtual table.
**
** The costs (WhereLoop.rRun) of the b-tree loops added by this function
** are calculated as follows:
**
** For a full scan, assuming the table (or index) contains nRow rows:
**
** cost = nRow * 3.0 // full-table scan
** cost = nRow * K // scan of covering index
** cost = nRow * (K+3.0) // scan of non-covering index
**
** where K is a value between 1.1 and 3.0 set based on the relative
** estimated average size of the index and table records.
**
** For an index scan, where nVisit is the number of index rows visited
** by the scan, and nSeek is the number of seek operations required on
** the index b-tree:
**
** cost = nSeek * (log(nRow) + K * nVisit) // covering index
** cost = nSeek * (log(nRow) + (K+3.0) * nVisit) // non-covering index
**
** Normally, nSeek is 1. nSeek values greater than 1 come about if the
** WHERE clause includes "x IN (....)" terms used in place of "x=?". Or when
** implicit "x IN (SELECT x FROM tbl)" terms are added for skip-scans.
*/
static int whereLoopAddBtree(
WhereLoopBuilder *pBuilder, /* WHERE clause information */
Bitmask mExtra /* Extra prerequesites for using this table */
){
WhereInfo *pWInfo; /* WHERE analysis context */
Index *pProbe; /* An index we are evaluating */
|
| ︙ | ︙ |