Jeff Janes <jeff.janes@xxxxxxxxx> writes: >> That sounds like you lack an index on the referencing column of the >> foreign key constraint. Postgres doesn't require you to keep such >> an index, but it's a really good idea if you ever update the referenced >> column. > For updating 20 million out of 500 million rows, wouldn't a full table > scan generally be preferable to an index scan anyway? Foreign key triggers do their checks retail, though, so you really want the probe for any referencing rows for a particular row-being-updated to be able to use an index. (It would be nice if we could replace that with a mass revalidation once it got to be a big fraction of the table, but we don't have a mechanism for that. Yet.) regards, tom lane -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
