Re: Possible TODO item? VACUUM on empty table

Greg Stark <gsstark(at)mit(dot)edu> writes:
> But not all of the stats are simple totals. I'm not sure this would make sense
> for the histogram arrays.

Yeah, I don't know how you "halve" a histogram.

But the problem is not with the pg_statistic stats, I think. It is
already true that ANALYZE punts without touching pg_statistic if it was
unable to find any live rows, and AFAIR it always has. So the problem
case of delete all/analyze doesn't clobber pg_statistic.

The issue is only with the relpages and reltuples counts in pg_class.
I already have a proposal on the table to get rid of these in favor of
a "tuples per page" entry, see eg
http://archives.postgresql.org/pgsql-general/2004-08/msg01422.php

An objection that I forgot to mention in that message is that any such
change would break autovacuum in its current form; although that issue
largely vanishes if we integrate autovacuum into the backend, and in any
case we could offer a built-in function to return the current number of
pages in a table.

regards, tom lane