mirrors/postgres
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Fix brain fade in cost estimation for index-only scans.

Browse Source 
visibility_fraction should not be applied to regular indexscans.
Noted by Cédric Villemain.
This commit is contained in:
Tom Lane 2011-10-08 10:41:17 -04:00
parent 1ef60dab70
commit b324384f6b
1 changed files with 9 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
src/backend/optimizer/path/costsize.c
View File

@ -264,6 +264,7 @@ cost_index(IndexPath *path, PlannerInfo *root,
if (!enable_indexscan) if (!enable_indexscan)
startup_cost += disable_cost; startup_cost += disable_cost;
/* we don't need to check enable_indexonlyscan; indxpath.c does that */
/* /*
* Call index-access-method-specific code to estimate the processing cost * Call index-access-method-specific code to estimate the processing cost
@ -345,7 +346,8 @@ cost_index(IndexPath *path, PlannerInfo *root,
(double) index->pages, (double) index->pages,
root); root);
pages_fetched = ceil(pages_fetched * visibility_fraction); if (indexonly)
pages_fetched = ceil(pages_fetched * visibility_fraction);
max_IO_cost = (pages_fetched * spc_random_page_cost) / num_scans; max_IO_cost = (pages_fetched * spc_random_page_cost) / num_scans;
@ -366,7 +368,8 @@ cost_index(IndexPath *path, PlannerInfo *root,
(double) index->pages, (double) index->pages,
root); root);
pages_fetched = ceil(pages_fetched * visibility_fraction); if (indexonly)
pages_fetched = ceil(pages_fetched * visibility_fraction);
min_IO_cost = (pages_fetched * spc_random_page_cost) / num_scans; min_IO_cost = (pages_fetched * spc_random_page_cost) / num_scans;
} }
@ -381,7 +384,8 @@ cost_index(IndexPath *path, PlannerInfo *root,
(double) index->pages, (double) index->pages,
root); root);
pages_fetched = ceil(pages_fetched * visibility_fraction); if (indexonly)
pages_fetched = ceil(pages_fetched * visibility_fraction);
/* max_IO_cost is for the perfectly uncorrelated case (csquared=0) */ /* max_IO_cost is for the perfectly uncorrelated case (csquared=0) */
max_IO_cost = pages_fetched * spc_random_page_cost; max_IO_cost = pages_fetched * spc_random_page_cost;
@ -389,7 +393,8 @@ cost_index(IndexPath *path, PlannerInfo *root,
/* min_IO_cost is for the perfectly correlated case (csquared=1) */ /* min_IO_cost is for the perfectly correlated case (csquared=1) */
pages_fetched = ceil(indexSelectivity * (double) baserel->pages); pages_fetched = ceil(indexSelectivity * (double) baserel->pages);
pages_fetched = ceil(pages_fetched * visibility_fraction); if (indexonly)
pages_fetched = ceil(pages_fetched * visibility_fraction);
min_IO_cost = spc_random_page_cost; min_IO_cost = spc_random_page_cost;
if (pages_fetched > 1) if (pages_fetched > 1)