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Overview
| Comment: | Remove the (undocumented) query-planner control that prevents a "SELECT ALL" subquery in FROM clause from being implemented as a co-routine. This control was added by [a29e117d7ec], where it was called a "stop-gap". |
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| Downloads: | Tarball | ZIP archive | SQL archive |
| Timelines: | family | ancestors | descendants | both | trunk |
| Files: | files | file ages | folders |
| SHA3-256: |
ff2f5a31a2ac67a2fdbb25793e8013cb |
| User & Date: | drh 2017-09-28 17:29:24 |
| Original Comment: | Remove the (undocumented) query-planner control that prevents a "SELECT ALL" subquery in FROM clause from being implemented as a co-routine. |
Context
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2017-09-29
| ||
| 12:12 | Better names for subqueries in EXPLAIN comments. check-in: 04ef40a8 user: drh tags: trunk | |
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2017-09-28
| ||
| 20:06 | Do not flatten subqueries that contain an ORDER BY or GROUP BY clause and can be implemented using a co-routine. check-in: 042d655d user: drh tags: prefer-coroutine-sort-subquery | |
| 17:29 | Remove the (undocumented) query-planner control that prevents a "SELECT ALL" subquery in FROM clause from being implemented as a co-routine. This control was added by [a29e117d7ec], where it was called a "stop-gap". check-in: ff2f5a31 user: drh tags: trunk | |
| 16:56 | Fix over-length source code lines in select.c. No logic changes. check-in: fd3267ef user: drh tags: trunk | |
Changes
Changes to src/select.c.
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}
/* Generate code to implement the subquery
**
** The subquery is implemented as a co-routine if all of these are true:
** (1) The subquery is guaranteed to be the outer loop (so that it
** does not need to be computed more than once)
** (2) The ALL keyword after SELECT is omitted. (Applications are
** allowed to say "SELECT ALL" instead of just "SELECT" to disable
** the use of co-routines.)
** (3) Co-routines are not disabled using sqlite3_test_control()
** with SQLITE_TESTCTRL_OPTIMIZATIONS.
**
** TODO: Are there other reasons beside (1) to use a co-routine
** implementation?
*/
if( i==0
&& (pTabList->nSrc==1
|| (pTabList->a[1].fg.jointype&(JT_LEFT|JT_CROSS))!=0) /* (1) */
&& (p->selFlags & SF_All)==0 /* (2) */
&& OptimizationEnabled(db, SQLITE_SubqCoroutine) /* (3) */
){
/* Implement a co-routine that will return a single row of the result
** set on each invocation.
*/
int addrTop = sqlite3VdbeCurrentAddr(v)+1;
pItem->regReturn = ++pParse->nMem;
|
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5313 5314 5315 5316 5317 5318 5319 5320 5321 5322 5323 5324 5325 5326 5327 5328 5329 5330 5331 5332 5333 5334 5335 5336 5337 |
}
/* Generate code to implement the subquery
**
** The subquery is implemented as a co-routine if all of these are true:
** (1) The subquery is guaranteed to be the outer loop (so that it
** does not need to be computed more than once)
** (2) REMOVED (2017-09-28): The ALL keyword after SELECT is omitted.
** (3) Co-routines are not disabled using sqlite3_test_control()
** with SQLITE_TESTCTRL_OPTIMIZATIONS.
**
** TODO: Are there other reasons beside (1) to use a co-routine
** implementation?
*/
if( i==0
&& (pTabList->nSrc==1
|| (pTabList->a[1].fg.jointype&(JT_LEFT|JT_CROSS))!=0) /* (1) */
/*** constraint removed: && (p->selFlags & SF_All)==0 (2) */
&& OptimizationEnabled(db, SQLITE_SubqCoroutine) /* (3) */
){
/* Implement a co-routine that will return a single row of the result
** set on each invocation.
*/
int addrTop = sqlite3VdbeCurrentAddr(v)+1;
pItem->regReturn = ++pParse->nMem;
|