Jeff Davis wrote: > On Thu, 2011-08-04 at 17:46 -0400, Bruce Momjian wrote: > > Right. I brought up SELECT INTO because you could make the argument > > that INSERT ... SELECT is not a utility command like the other ones and > > therefore can't be done easily, but CREATE TABLE AS is internal SELECT > > INTO and implemented in execMain.c, which I think is where INSERT ... > > SELECT would also be implemented. > > The above statement is a little confusing, so let me start from the > beginning: > > How could we avoid WAL logging for INSERT ... SELECT? > > The way we do it for CREATE TABLE AS is because nobody would even *see* > the table if our transaction doesn't commit. Therefore we don't need to > bother logging it. Same can be said for SELECT INTO. > > INSERT ... SELECT is just an insert. It needs just as much logging as > inserting tuples any other way. For instance, it will potentially share > pages with other inserts, and better properly record all such page > modifications so that they return to a consistent state.
It would act like COPY, meaning the table would have to be truncated or created in the same transaction. -- Bruce Momjian <br...@momjian.us> http://momjian.us EnterpriseDB http://enterprisedb.com + It's impossible for everything to be true. + -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
