On 7/30/16 10:47 AM, Tom Lane wrote: > Pavel Stehule <pavel.steh...@gmail.com> writes: >> But there are some patterns used with work with temp tables,that should not >> working, and we would to decide if we prepare workaround or not. > >> -- problematic pattern (old code) >> IF NOT EXISTS(SELECT * FROM pg_class WHERE ....) THEN >> CREATE TEMP TABLE xxx() >> ELSE >> TRUNCATE TABLE xxx; >> END IF; > >> -- modern patter (new code) >> BEGIN >> TRUNCATE TABLE xxx; >> EXCEPTION WHEN ..... THEN >> CREATE TEMP TABLE(...) >> END; > > If the former stops working, that's a sufficient reason to reject the > patch: it hasn't been thought through carefully enough. The key reason > why I don't think that's negotiable is that if there aren't (apparently) > catalog entries corresponding to the temp tables, that will almost > certainly break many things in the backend and third-party extensions, > not only user code patterns like this one. We'd constantly be fielding > bug reports that "feature X doesn't work with temp tables anymore". > > In short, I think that the way to make something like this work is to > figure out how to have "virtual" catalog rows describing a temp table. > Or maybe to partition the catalogs so that vacuuming away temp-table > rows is easier/cheaper than today.
In addition the latter pattern burns an xid which can be a problem for high-volume databases. How about CREATE TEMP TABLE IF NOT EXISTS...? -- -David da...@pgmasters.net -- Sent via pgsql-hackers mailing list (email@example.com) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers