Scott Marlowe <scott.marlowe@xxxxxxxxx> writes: > On Tue, Nov 25, 2014 at 1:58 PM, Heikki Linnakangas > <hlinnakangas@xxxxxxxxxx> wrote: >> I don't know why this regressed between those versions, but looking at the >> functions, there's some low-hanging fruit: >> >> 1. tree_ancestor_keys() could use UNION ALL instead of UNION. (I believe >> duplicates are expected here, although I'm not 100% sure). >> >> 2. tree_ancestor_keys() calculates tree_level($1) every time it recurses. >> Would be cheaper to calculate once, and pass it as argument. > Wow that made a huge difference. About a 50% increase across the > board. Sadly, 9.2 is still way behind 8.4 (see Tom's email) Switching from UNION to UNION ALL would dodge the varbit hash-opclass caching issue, I think. But there's still something else going on. regards, tom lane -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
