On Mon, Mar 09, 2020 at 09:51:21AM +0100, Josef Machytka wrote: > We are lately experiencing very strange locks on PostgreSQL 11.7 when we > process ETL tasks using our programs in Go 1.13.8 using standard libraries > sql and pq. > > ETL task has to rename tables but PostgreSQL shows that this simple > operation waits for Lock on relation and select from PG wiki ( > https://wiki.postgresql.org/wiki/Lock_Monitoring) which should show > blocking process shows that command "alter table .... rename to ...." is > blocked by process "COPY .... to stdout" but from completely different > table. > > And from time to time even selects from some tables seem to by blocked by > copy commands running on other tables. This is shown by the same select > from PG wiki for blocking queries. > > All this stuff runs from golang programs. So maybe problem is not on > PostgreSQL but in golang libraries? The query displayed is just the query currently executing, but if the connection is in a transaction the problematic lock could have been acquired by any previously executed query. Did you check in pg_stat_activity if the connection is in a transaction (e.g. query_start != xact_start)?
