Merlin Moncure wrote: > On Tue, Aug 2, 2011 at 8:34 AM, Bruce Momjian <br...@momjian.us> wrote: > > Our docs suggest an optimization to reduce WAL logging when you are > > creating and populating a table: > > > > ? ? ? > > ?http://www.postgresql.org/docs/9.0/static/runtime-config-wal.html#RUNTIME-CONFIG-WAL-SETTINGS > > > > ? ? ? ?In minimal level, WAL-logging of some bulk operations, like CREATE > > ? ? ? ?INDEX, CLUSTER and COPY on a table that was created or truncated in > > the > > ? ? ? ?same transaction can be safely skipped, which can make those > > operations > > ? ? ? ?much faster (see Section 14.4.7). But minimal WAL does not contain > > ? ? ? ?enough information to reconstruct the data from a base backup and the > > ? ? ? ?WAL logs, so either archive or hot_standby level must be used to > > enable > > ? ? ? ?WAL archiving (archive_mode) and streaming replication. > > > > I am confused why we issue significant WAL traffic for CREATE INDEX? > > Isn't the index either created or removed if the transaction fails? > > What crash recovery activity state do we need WAL logging for? ?I > > realize we have to do WAL logging for streaming replication, but CREATE > > TABLE isn't going to affect that. ? I also realize the index has to be > > on disk on commit, but the same is true for doing the CREATE TABLE in > > the same transaction block. > > > > Does this optimization work for INSERT ... SELECT? > > I don't think so -- insert/select doesn't take a full table lock and > it writes to the heap. The optimization only works when other
My question is whether INSERT ... SELECT is/could be optimized when the CREATE TABLE happens in the same transaction block. -- 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
