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/include/access | |
| 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/access')
| -rw-r--r-- | src/include/access/visibilitymap.h | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/src/include/access/visibilitymap.h b/src/include/access/visibilitymap.h index 7d62c126407..4e5c0a0e4ed 100644 --- a/src/include/access/visibilitymap.h +++ b/src/include/access/visibilitymap.h @@ -27,6 +27,7 @@ extern bool visibilitymap_pin_ok(BlockNumber heapBlk, Buffer vmbuf); extern void visibilitymap_set(Relation rel, BlockNumber heapBlk, XLogRecPtr recptr, Buffer vmbuf); extern bool visibilitymap_test(Relation rel, BlockNumber heapBlk, Buffer *vmbuf); -extern void visibilitymap_truncate(Relation rel, BlockNumber heapblk); +extern BlockNumber visibilitymap_count(Relation rel); +extern void visibilitymap_truncate(Relation rel, BlockNumber nheapblocks); #endif /* VISIBILITYMAP_H */ |