On Sun, Mar 11, 2018 at 9:49 AM, Tom Lane <t...@sss.pgh.pa.us> wrote: > Andrew Dunstan <andrew.duns...@2ndquadrant.com> writes: >> Why does VACUUM FULL cause the size of this table with a single >> dropped column (1 out of 1000) cause the table size to double? > > VACUUM FULL will rewrite the tuples with a null bitmap where they > had none before (cf reform_and_rewrite_tuple). That's only a rather > marginal increase in the tuple size, but in this particular example, > it pushes the tuples from just under half a page to just over, so > that you go from 2 tuples/page to 1. >
Aha! Thanks for the explanation. cheers andrew -- Andrew Dunstan https://www.2ndQuadrant.com PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
