On Fri, Mar 11, 2011 at 8:07 PM, Bruce Momjian <br...@momjian.us> wrote: > Currently, if you create a temporary table with the ON COMMIT action of > DELETE ROWS, the table will truncated for every commit, whether there is > any data in the table or not. > > I measured the overhead using this test: > > $ (echo 'CREATE TEMPORARY TABLE TEST2 (x int);'; jot -b 'SELECT 1;' > 10000) | time psql test > /dev/null > 6.93 real 0.93 user 0.78 sys > $ (echo 'CREATE TEMPORARY TABLE TEST2 (x int) ON COMMIT DELETE ROWS;'; > jot -b 'SELECT 1;' 10000) | time psql test > /dev/null > 7.93 real 1.02 user 0.72 sys > > The overhead measures 14%. Is there a simple way to avoid the repeated > truncation overhead of such cases? Is this a TODO?
We might be able to make PreCommit_on_commit_actions() exit quickly without doing anything if MyXactAccessedTempRel is false. I haven't tested that solution and am not 100% confident that it's safe, but if it is I believe it would address your concern. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
