ERROR: canceling autovacuum task
CONTEXT: automatic vacuum of table "metadb.test.transactions"
Are these happening regularly? They indicate that something is
happening on the table that collides with what autovacuum needs to do,
and autovacuum defers its task. For this to happen you need to be doing
ALTER TABLE or similar however; normal UPDATE/INSERT/DELETE should not
cause autovacuum to cancel itself.
I am not using an ALTER table command but I am doing periodic ANALYZEs
to evaluate the table size. Could this be causing the problem? I notice
that stopping the ANALYZE calls appears to eliminate the canceled
autovacuum.
What concerns me is that once the size has grown, even a VACUUM FULL
doesn't recover the space. Regular external VACUUMs keep the table at
around 10MB but if I use autovacuum and it grows to 40MB, a VACUUM FULL
will only get it down to 35MB. Is it possible that a canceled autovacuum
could result in permanently lost space?
Out of interest, what kind of fragmentation overhead should I expect if
I have a table in which I maintain a fixed number of rows. eg. A 20000
row table which is 6MB before rows are wrapped out will obviously use a
larger disk footprint as rows are added and deleted. Anyone have a rule
of thumb which works for them?
Thanks for the response,
Stuart
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