Re: Avoiding redundant fetches of btree index metapages

Tom Lane wrote:
> Some experimentation over the weekend turned up the result that $SUBJECT 
> is a good idea.  I had never thought about this much before, figuring
> that in a heavily-used index the metapage would stay in cache anyway and
> so fetching it at the start of each index search isn't costing any extra
> I/O.  That's true, but what it does cost is bufmgr contention, and in
> fact more than you'd expect because the amount of work actually done
> before releasing the page again is minuscule.  (See off-list discussion
> attached below.)

Wow, this is extremely nice.  Congratulations on another well-spotted
performance problem solved.

-- 
Alvaro Herrera                                http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support