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Overview
| Comment: | Do not do full table scans of unordered indices. |
|---|---|
| Downloads: | Tarball | ZIP archive | SQL archive |
| Timelines: | family | ancestors | descendants | both | trunk |
| Files: | files | file ages | folders |
| SHA1: |
a8761a9128de945aa4b6196df5ffe641 |
| User & Date: | drh 2011-04-15 14:46:27 |
References
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2011-04-15
| ||
| 15:18 | Backport check-in [9f9f32882501ac9] to provide EXPLAIN QUERY PLAN output for the count(*) optimization. Also backport check-in [a8761a9128de945aa] to prevent unordered indices from being used on a full table scan. The first backport was necessary in order to test the second. (check-in: 8d924e16 user: drh tags: branch-3.7.2) | |
Context
|
2011-04-15
| ||
| 16:39 | Changes to memory allocator usage tracking to delay the onset of integer overflow. (check-in: 4e33a0ea user: drh tags: trunk) | |
| 14:46 | Do not do full table scans of unordered indices. (check-in: a8761a91 user: drh tags: trunk) | |
| 14:33 | Fix #ifs involving SQLITE_ENABLE_LOCKING_STYLE so that they check the value of that macro and not whether it is defined. (check-in: 8775f159 user: drh tags: trunk) | |
Changes
Changes to src/select.c.
4234 4235 4236 4237 4238 4239 4240 4241 4242 4243 4244 4245 4246 4247 4248 4249 4250 4251 4252 4253 |
/* Search for the index that has the least amount of columns. If
** there is such an index, and it has less columns than the table
** does, then we can assume that it consumes less space on disk and
** will therefore be cheaper to scan to determine the query result.
** In this case set iRoot to the root page number of the index b-tree
** and pKeyInfo to the KeyInfo structure required to navigate the
** index.
**
** In practice the KeyInfo structure will not be used. It is only
** passed to keep OP_OpenRead happy.
*/
for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
if( !pBest || pIdx->nColumn<pBest->nColumn ){
pBest = pIdx;
}
}
if( pBest && pBest->nColumn<pTab->nCol ){
iRoot = pBest->tnum;
pKeyInfo = sqlite3IndexKeyinfo(pParse, pBest);
}
|
> > | |
4234 4235 4236 4237 4238 4239 4240 4241 4242 4243 4244 4245 4246 4247 4248 4249 4250 4251 4252 4253 4254 4255 |
/* Search for the index that has the least amount of columns. If
** there is such an index, and it has less columns than the table
** does, then we can assume that it consumes less space on disk and
** will therefore be cheaper to scan to determine the query result.
** In this case set iRoot to the root page number of the index b-tree
** and pKeyInfo to the KeyInfo structure required to navigate the
** index.
**
** (2011-04-15) Do not do a full scan of an unordered index.
**
** In practice the KeyInfo structure will not be used. It is only
** passed to keep OP_OpenRead happy.
*/
for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
if( pIdx->bUnordered==0 && (!pBest || pIdx->nColumn<pBest->nColumn) ){
pBest = pIdx;
}
}
if( pBest && pBest->nColumn<pTab->nCol ){
iRoot = pBest->tnum;
pKeyInfo = sqlite3IndexKeyinfo(pParse, pBest);
}
|
Changes to test/unordered.test.
53 54 55 56 57 58 59 60 61 62 63 64 65 |
5 "SELECT group_concat(b) FROM t1 GROUP BY a"
{0 0 0 {SCAN TABLE t1 USING INDEX i1 (~128 rows)}}
{0 0 0 {SCAN TABLE t1 (~128 rows)} 0 0 0 {USE TEMP B-TREE FOR GROUP BY}}
6 "SELECT * FROM t1 WHERE a = ?"
{0 0 0 {SEARCH TABLE t1 USING INDEX i1 (a=?) (~1 rows)}}
{0 0 0 {SEARCH TABLE t1 USING INDEX i1 (a=?) (~1 rows)}}
} {
do_eqp_test 1.$idxmode.$tn $sql $r($idxmode)
}
}
finish_test
|
> > > |
53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 |
5 "SELECT group_concat(b) FROM t1 GROUP BY a"
{0 0 0 {SCAN TABLE t1 USING INDEX i1 (~128 rows)}}
{0 0 0 {SCAN TABLE t1 (~128 rows)} 0 0 0 {USE TEMP B-TREE FOR GROUP BY}}
6 "SELECT * FROM t1 WHERE a = ?"
{0 0 0 {SEARCH TABLE t1 USING INDEX i1 (a=?) (~1 rows)}}
{0 0 0 {SEARCH TABLE t1 USING INDEX i1 (a=?) (~1 rows)}}
7 "SELECT count(*) FROM t1"
{0 0 0 {SCAN TABLE t1 USING COVERING INDEX i1(~128 rows)}}
{0 0 0 {SCAN TABLE t1 (~128 rows)}}
} {
do_eqp_test 1.$idxmode.$tn $sql $r($idxmode)
}
}
finish_test
|