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. Branch ------ master Details ------- http://git.postgresql.org/pg/commitdiff/e6858e665731c0f56d3ecc9fbb245c32d24f8ef7 Modified Files -------------- doc/src/sgml/catalogs.sgml | 13 ++++++ src/backend/access/hash/hash.c | 3 +- src/backend/access/heap/visibilitymap.c | 68 +++++++++++++++++++++++++++++++ src/backend/catalog/heap.c | 4 ++ src/backend/catalog/index.c | 52 ++++++++++++++++------- src/backend/commands/analyze.c | 11 ++++- src/backend/commands/cluster.c | 5 ++ src/backend/commands/vacuum.c | 6 +++ src/backend/commands/vacuumlazy.c | 20 ++++++++- src/backend/nodes/outfuncs.c | 1 + src/backend/optimizer/path/costsize.c | 18 ++++----- src/backend/optimizer/util/plancat.c | 30 ++++++++++++- src/backend/optimizer/util/relnode.c | 2 + src/backend/utils/cache/relcache.c | 2 + src/include/access/visibilitymap.h | 3 +- src/include/catalog/catversion.h | 2 +- src/include/catalog/pg_class.h | 45 +++++++++++--------- src/include/commands/vacuum.h | 1 + src/include/nodes/relation.h | 4 +- src/include/optimizer/plancat.h | 2 +- src/test/regress/expected/window.out | 23 +++++----- src/test/regress/sql/window.sql | 3 +- 22 files changed, 246 insertions(+), 72 deletions(-) -- Sent via pgsql-committers mailing list (pgsql-committers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-committers