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Avoid useless work during set_plain_rel_pathlist() when the relation 

will be excluded by constraint exclusion anyway.  Greg Stark
This commit is contained in:
Tom Lane 2007-04-21 06:18:52 +00:00
parent 925ca9d7de
commit 48239e156f
1 changed files with 22 additions and 20 deletions
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42
src/backend/optimizer/path/allpaths.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/path/allpaths.c,v 1.161 2007/02/22 22:00:23 tgl Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/path/allpaths.c,v 1.162 2007/04/21 06:18:52 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -196,6 +196,25 @@ set_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, Index rti)
static void
set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
{
/*
* If we can prove we don't need to scan the rel via constraint exclusion,
* set up a single dummy path for it. (Rather than inventing a special
* "dummy" path type, we represent this as an AppendPath with no members.)
*/
if (relation_excluded_by_constraints(rel, rte))
{
/* Set dummy size estimates --- we leave attr_widths[] as zeroes */
rel->rows = 0;
rel->width = 0;
add_path(rel, (Path *) create_append_path(rel, NIL));
/* Select cheapest path (pretty easy in this case...) */
set_cheapest(rel);
return;
}
/* Mark rel with estimated output rows, width, etc */
set_baserel_size_estimates(root, rel);
@ -210,24 +229,6 @@ set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
if (create_or_index_quals(root, rel))
set_baserel_size_estimates(root, rel);
/*
* If we can prove we don't need to scan the rel via constraint exclusion,
* set up a single dummy path for it. (Rather than inventing a special
* "dummy" path type, we represent this as an AppendPath with no members.)
*/
if (relation_excluded_by_constraints(rel, rte))
{
/* Reset output-rows estimate to 0 */
rel->rows = 0;
add_path(rel, (Path *) create_append_path(rel, NIL));
/* Select cheapest path (pretty easy in this case...) */
set_cheapest(rel);
return;
}
/*
* Generate paths and add them to the rel's pathlist.
*
@ -369,7 +370,8 @@ set_append_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
/*
* Propagate size information from the child back to the parent. For
* simplicity, we use the largest widths from any child as the parent
* estimates.
* estimates. (If you want to change this, beware of child
* attr_widths[] entries that haven't been set and are still 0.)
*/
rel->rows += childrel->rows;
if (childrel->width > rel->width)