On 12/12/2012 05:12 PM, Andrew Dunstan wrote:
On 12/12/2012 04:32 PM, Tom Lane wrote:
Andrew Dunstan <andrew@xxxxxxxxxxxx> writes:
A client is testing a migration from 9.1 to 9.2, and has found that a
large number of queries run much faster if they use index-only scans.
However, the only way he has found to get such a plan is by increasing
the seq_page_cost to insanely high levels (3.5). Is there any approved
way to encourage such scans that's a but less violent than this?
Is the pg_class.relallvisible estimate for the table realistic? They
might need a few more VACUUM and ANALYZE cycles to get it into the
neighborhood of reality, if not.
That was the problem - I didn't know this hadn't been done.
Actually, the table had been analysed but not vacuumed, so this kinda
begs the question what will happen to this value on pg_upgrade? Will
people's queries suddenly get slower until autovacuum kicks in on the table?
cheers
andrew
--
Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-performance
