Re: unusual performance for vac following 8.2 upgrade

Hey Tom,
We were running on 8.1.1 previous to upgrading to 8.2, and yes, we
definitely have a heafty pg_class. The inheritance model is heavily used
in our schema (the results of the group by you wanted to see are down
below). However, no significant problems were seen with vacs while we
were on 8.1. Execution time for the vac seemed more linked to large
table size and how active the table was with updates, rather than being
universally over 10 minutes regardless of the vac's object. We will be
doing an audit of our 8.2 install to try and make sure that it looks
like a complete install, any tests you can think of that may further
narrow things down for us?

relkind | count
---------+--------
v | 1740
t | 49986
c | 4
S | 57
r | 108689
i | 374723
(6 rows)

Tom Lane wrote:

>Kim <kim(at)myemma(dot)com> writes:
>
>
>>size of pg_class: 535,226
>>number of relations: 108,694
>>
>>
>
>Oh, I shoulda read all the way to the bottom of your email :-(. What
>version of PG were you running before? I would think that pretty much
>any version of pgstat_vacuum_tabstats would have had a performance issue
>with pg_class that large. Also, could we see
>
> select relkind, count(*) from pg_class group by relkind;
>
> regards, tom lane
>
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