[fedora-arm] Arm-Koji buildsystem will be down for maintenance

[Peter Robinson]

On Fri, Nov 16, 2012 at 7:00 PM, Chris Tyler <chris at tylers.info> wrote:
> On Fri, 2012-11-16 at 13:41 -0500, Jon Masters wrote:
>> So, can you perhaps provide a bit more detail? We know you've been
>> looking at options around the tables, but...more info?
>
> Long story short: db dump & reload for storage packing, with an LVM
> snapshot as a safety net; should be done in about 20 minutes. Tests on a
> parallel machine show a 500x performance improvement.

500x on a box without random queries coming from all over, I suspect
it won't be as impressive on production. I suspect you'll get pretty
decent perf improvements if you drop and recreate the indexes and
vacuum the DB.

> (Investigations into PostgreSQL being insanely brain-dead continue.
> Example: query strategy for "SELECT COUNT(*) FROM FOO;" involves a
> "Sequential scan over 1496312 records." Srsly?)

Probably either a bad index or a lack of an index in the right spot.

Peter