On Sun, May 09, 2004 at 09:50:00AM +0800, Christopher Kings-Lynne wrote: > >What does the MERGE command do? I have never heard of it, so I doubt > >someone is working on it. > > It is basically the SQL standard version of MySQL's REPLACE syntax. It > does an update-else-insert set. However, the trick is that it uses some > sort of next key locking to ensure that it cannot fail. Something that > is impossible to do in PostgreSQL at the moment. Nested transactions > will help, however.
I intend to release locks on subtransaction abort, so if the update fails there's room for another transaction to insert the key (which I understand should fail?). I guess there's a different locking mechanism needed; I believe nested transactions will not be enough. -- Alvaro Herrera (<alvherre[a]dcc.uchile.cl>) "The first of April is the day we remember what we are the other 364 days of the year" (Mark Twain) ---------------------------(end of broadcast)--------------------------- TIP 8: explain analyze is your friend
