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| 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/include/commands | |
| 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/include/commands')
| -rw-r--r-- | src/include/commands/vacuum.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/src/include/commands/vacuum.h b/src/include/commands/vacuum.h index cfbe0c4392..d8fd0caa6b 100644 --- a/src/include/commands/vacuum.h +++ b/src/include/commands/vacuum.h @@ -149,6 +149,7 @@ extern double vac_estimate_reltuples(Relation relation, bool is_analyze, extern void vac_update_relstats(Relation relation, BlockNumber num_pages, double num_tuples, + BlockNumber num_all_visible_pages, bool hasindex, TransactionId frozenxid); extern void vacuum_set_xid_limits(int freeze_min_age, int freeze_table_age, |