On Fri, Sep 22, 2017 at 5:44 AM, Igor Neyman <iney...@perceptron.com> wrote: > I think the difference between pg_current_wal_lsn() and confirmed_flush_lsn > form pg_catalog.pg_replication_slots for specific replication slot: > > SELECT (pg_current_wal_lsn() - confirmed_flush_lsn) AS lsn_distance > FROM pg_catalog.pg_replication_slots > WHERE slot_name = '<some_subscibtion_name>'; > > provides a measure in Logical Replication environment of how far did (or did > not) Subscriber fell behind Publisher, and hence some kind of measure of how > much "extra" WALs is stored on the Publisher.
More or less. I also make use of the value of max_wal_size in pg_settings to do the decision-making, value set depending on a fraction of the size of the partition dedicated to pg_xlog. By applying pg_size_bytes() which is new to 9.6 on top of the value fetched from pg_settings you can make a direct comparison and decide if a slot can be dropped or not. Make sure that things are casted to bigint though. -- Michael -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
