Re: Queries Per Second (QPS)

On 09/26/2015 09:24 AM, Adam Scott wrote:
> How do we measure queries per second (QPS), not transactions per second,
> in PostgreSQL without turning on full logging which has a performance
> penalty and can soak up lots of disk space?

Measure it from the client side.  pgBench does this.

If you mean on your production workload, then I recommend using a
connection proxy which counts statements.  A few exist for Postgres, for
example:

VividCortex:
https://www.vividcortex.com/blog/2015/05/13/announcing-vividcortex-network-analyzer-mysql-postgresql/

WireShark: https://github.com/dalibo/pgshark

You'd need to measure how much one of these tools affects your QPS, of
course, but that should be easily measurable on a test system.

Also, if the PostgresQL activity log is moved to a seperate SSD from the
database storage, I've found overhead in writing to it to be less than
3% ... depending on the nature of your query traffic.  Pathological
situations are mainly databases which have a high volume of very long
queries or failed connection attempts.

>
> We are using 8.4, but I'm interested in any version as well.

You are aware that 8.4 is EOL, yes?  Not to mention missing 5 years of
performance improvements ...

--
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com