On Fri, May 10, 2019 at 12:41 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
Andres Freund <andres@anarazel.de> writes: > On 2019-05-09 13:03:50 -0700, Erik Jones wrote: >> The question then is: Why would these user queries be waiting on an >> AccessShare lock on pg_attribute?
> Queries that access a table for the *first* time after DDL happened > (including truncating the relation), need an AccessShareLock on > pg_attribute (and pg_class, pg_index, ...) for a short time.
Also, it seems likely that what's really triggering the issue is autovacuum on pg_attribute trying to truncate off empty pages in pg_attribute (after a bunch of dead rows were generated there by DDL activity). That requires exclusive lock on pg_attribute, which would propagate down to the standby.
regards, tom lane
Right, that part I understood after checking out pg_attribute's insert/delete counts in pg_stat_sys_tables before and after some REFRESH MATERIALIZED VIEW runs on an otherwise idle server. With them running 2k+ refreshes per day autovac is regularly working on their catalog tables.