marcin kowalski <yoshi314@xxxxxxxxx> writes: > I am experiencing an odd issue, i've noticed it on 9.3 , but i can reproduce it on 9.6. > > Basically, i have a database with a lot of schemas, but not that much data. Each schema is maybe 2-4 GB in size, and often much less than that. > > The database has ~300-500 schemas, each with ~100-300 tables. Generally a few hundred thousand tables total. Entire cluster has 2 or 3 such databases. > > As the amount of tables grows, the time it takes to vacuum an _empty_ table grows as well. The table is in public schema, and it is the only table there. I presume since vacuum then has much larger catalogs to query as if to find indexes and related toast tables to process along with your table of interest. > I made a simple testing script to make sure that these things are related. I set up a blank database, create a table with one column in public and restore one schema. > Then i vacuum that table three times, measure the execution times and repeat the process, adding another schema to db. > > At ~200 tables it takes ~100ms for psql to issue a vacuum verbose and exit. At 83K tables the time is already at ~1.5second. The progress appars to be directly > proportional to table amount, and grows linearly, eventually crossing past 3seconds - for blank table with no data. > > I think this may severely impact the entire vacuumdb run, but i have not verified that yet. > > This is irrelevant of amount of data restored, i am seeing the same behavior with just schema restore, as well as with schema+data restores. > > If anyone is interested i may upload the schema data + my benchmarking script with collected whisper data from my test run (i've been plotting it in grafana via carbon) > > Is this a known issue? Can i do anything to improve performance here? > -- Jerry Sievers Postgres DBA/Development Consulting e: postgres.consulting@xxxxxxxxxxx p: 312.241.7800 -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
