Frequently Asked question¶
Can I use PoWA on a standby server, or store the data on an external server¶
Yes! Since version 4 of PoWA, it’s possible to setup a remote snapshot, thus aggregating all the performance data on a dedicated remote PostgreSQL server. This mode greatly limits the performance impact of PoWA on the configured servers, and also allows to use PoWA on standby servers too. See the Remote setup documentation more details.
Some queries don’t show up in the UI¶
That’s a know limitation with the current implementation of powa-web.
For now, the UI will only display information about queries that have been run on at least two distinct snapshots of powa-archivist (parameter powa.frequency). With default settings, that means you need to run activity for at least 10 minutes.
This is however usually not a problem since queries only executed a few time and never again are not really a target for optimization.
I ran some queries and index suggestion doesn’t suggest any index¶
With default configuration, pg_qualstats will only sample 1% of the queries. This default value is a safeguard to avoid overhead on heavily loaded production server. However, if you’re just doing some test that means that you’ll miss most of the WHERE and JOIN clauses, and index suggestion won’t be able to suggest indexes.
If you want pg_qualstats to sample every query, you need to configure pg_qualstats.sample_rate = 1 in the postgresql.conf configuration file, and reload the configuration.
Please keep in mind that such a configuration can have a strong impact on the performance, especially if a lot of concurrent and fast queries are executed.