diff options
| author | Tom Lane | 2011-10-14 21:23:01 +0000 |
|---|---|---|
| committer | Tom Lane | 2011-10-14 21:23:46 +0000 |
| commit | e6858e665731c0f56d3ecc9fbb245c32d24f8ef7 (patch) | |
| tree | 4df2705d53d53b1bbd7a14d7017cb519d82ee227 /src/backend/commands/vacuum.c | |
| parent | dea95c7a7beb5ef66ce89269dd0e84d0c26e5523 (diff) | |
Measure the number of all-visible pages for use in index-only scan costing.
Add a column pg_class.relallvisible to remember the number of pages that
were all-visible according to the visibility map as of the last VACUUM
(or ANALYZE, or some other operations that update pg_class.relpages).
Use relallvisible/relpages, instead of an arbitrary constant, to estimate
how many heap page fetches can be avoided during an index-only scan.
This is pretty primitive and will no doubt see refinements once we've
acquired more field experience with the index-only scan mechanism, but
it's way better than using a constant.
Note: I had to adjust an underspecified query in the window.sql regression
test, because it was changing answers when the plan changed to use an
index-only scan. Some of the adjacent tests perhaps should be adjusted
as well, but I didn't do that here.
Diffstat (limited to 'src/backend/commands/vacuum.c')
| -rw-r--r-- | src/backend/commands/vacuum.c | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c index 7fe787ecb74..f42504cf9fd 100644 --- a/src/backend/commands/vacuum.c +++ b/src/backend/commands/vacuum.c @@ -569,6 +569,7 @@ vac_estimate_reltuples(Relation relation, bool is_analyze, void vac_update_relstats(Relation relation, BlockNumber num_pages, double num_tuples, + BlockNumber num_all_visible_pages, bool hasindex, TransactionId frozenxid) { Oid relid = RelationGetRelid(relation); @@ -599,6 +600,11 @@ vac_update_relstats(Relation relation, pgcform->reltuples = (float4) num_tuples; dirty = true; } + if (pgcform->relallvisible != (int32) num_all_visible_pages) + { + pgcform->relallvisible = (int32) num_all_visible_pages; + dirty = true; + } if (pgcform->relhasindex != hasindex) { pgcform->relhasindex = hasindex; |