Tracking table modifications / table stats

On Thu, Mar 3, 2011 at 11:00 AM, Derrick Rice <derrick.rice@gmail.com> wrote:

Hey folks,

I was looking through the contrib modules with 8.4 and hoping to find
something that satisfies my itch.
http://www.postgresql.org/docs/8.4/static/pgstatstatements.html comes the
closest.

I'm inheriting a database which has mostly unknown usage patterns, and would
like to figure them out so that I can allocate tablespaces and set
autovacuum settings appropriately.  To do this, it seems I need to know (at
least) the number of rows read, rows updated, rows deleted, and rows
inserted for each table (over time, or until reset).

I suppose things like disk usage and CPU usage would be interesting as well,
but I'm somewhat less concerned with those.  For one, CPU usage can't be
tied to a table as easily and is more about query optimization than
PostgreSQL configuration (excluding cost coefficients and memory size
settings).  For the other, disk usage can be mostly inferred from the row
size and and number of operations per table (this does exclude seq. scans
and heavy heavy index use, though).  I realize those statements are fuzzy
and short-sighted, but I'm trying to get "good enough" information, not
optimize a space shuttle.

There's no way I'm the first person to feel the need for this.  Is there a
doc or wiki which gives some recommendations?  I'd like to avoid parsing
logs or installing triggers.  I'd also like to avoid heavy statement-level
tracking like the above mentioned contrib does (sounds expensive, and I'm
not sure the users have parameterized SQL).

The old tried and true method of slow query logging
(min_statement_duration) works wonders. Usually in a typical system
10% of the queries are doing 90% of the work.

If I'm coming into a new database created by someone else, priority #1
is to get logging under control: make sure it's being captured,
rotated properly, etc. If there are lots of garbage errors being
dropped in there, try fixing them so that the logs become useful.

merlin

On 3/3/2011 11:00 AM, Derrick Rice wrote:

Hey folks,

I was looking through the contrib modules with 8.4 and hoping to find
something that satisfies my itch.
http://www.postgresql.org/docs/8.4/static/pgstatstatements.html comes
the closest.

I'm inheriting a database which has mostly unknown usage patterns, and
would like to figure them out so that I can allocate tablespaces and set
autovacuum settings appropriately. To do this, it seems I need to know
(at least) the number of rows read, rows updated, rows deleted, and rows
inserted for each table (over time, or until reset).

I suppose things like disk usage and CPU usage would be interesting as
well, but I'm somewhat less concerned with those. For one, CPU usage
can't be tied to a table as easily and is more about query optimization
than PostgreSQL configuration (excluding cost coefficients and memory
size settings). For the other, disk usage can be mostly inferred from
the row size and and number of operations per table (this does exclude
seq. scans and heavy heavy index use, though). I realize those
statements are fuzzy and short-sighted, but I'm trying to get "good
enough" information, not optimize a space shuttle.

There's no way I'm the first person to feel the need for this. Is there
a doc or wiki which gives some recommendations? I'd like to avoid
parsing logs or installing triggers. I'd also like to avoid heavy
statement-level tracking like the above mentioned contrib does (sounds
expensive, and I'm not sure the users have parameterized SQL).

Thanks,

Derrick

There are stat tables you can look at:

http://www.postgresql.org/docs/9.0/static/monitoring-stats.html

-Andy

On Thu, Mar 3, 2011 at 12:34 PM, Andy Colson
<andy@squeakycode.net>wrote:There are stat tables you can look at:

http://www.postgresql.org/docs/9.0/static/monitoring-stats.html

-Andy

Aha! Thank you.