We couldn't get plans for this query, presumably because some parameters are missing: relation "core_departurecalculationtask" does not exist

[tarkhil]

Hello

I'm using powa on a moderately complex database with several schemas and search_path set appropriately for all users.

However, requests are stored by powa without full specification and powa-web cannot analyze SOME queries. That's another mystery, for some are analyzed.

What could be wrong?

[rjuju]

There are multiple reasons that could explain a failure in getting this kind of error.

First of all, powa gets the data (which here is the normalized query text) from pg_stat_statements, and that extensions normalize the query string as-is, without trying to fully qualify object or store the associated search_path at the time the query text is stored. This has already been discussed in the past (see for instance https://www.postgresql.org/message-id/flat/9baf5c06-d6ab-c688-010c-843348e3d98c%40gmail.com for the last one I remember), but unfortunately none of the committer is interested in that topic nothing was ever done.

Note also that pg_stat_statements stores the first query string associated to an entry, so if you sometime use the search_path and sometime rely on fully qualified objects for the exact same queryid, you may or may not get a useful entry.

Since the error is relation "core_departurecalculationtask" does not exist, I'm assuming that either that table does not exist anymore (maybe a temporary table or a table dropped since), or more likely it was stored by pg_stat_statements using a non default search_path.

Maybe it works for some other queries because the saved query text was qualified, or because there's a matching relation relation name (not necessarily the same object as the one in the query though) in the connection default search_path.

Unfortunately there isn't much we can do without change in pg_stat_statements. The only possibility on the powa side would be to let users manually tag the queries with a search_path, but it looks like a lot of error-prone work for users.