On 13 December 2012 03:51, Tom Lane <t...@sss.pgh.pa.us> wrote: > ANALYZE does not set that value, and is not going to start doing so, > because it doesn't scan enough of the table to derive a trustworthy > value.
I'm slightly surprised by your remarks here, because the commit message where the relallvisible column was added (commit a2822fb9337a21f98ac4ce850bb4145acf47ca27) says: "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." Have I missed some nuance? -- Peter Geoghegan http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training and Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
