Hi, Thanks for the helpful comments!
On Wed, Dec 17, 2008 at 8:50 PM, Simon Riggs <si...@2ndquadrant.com> wrote: > > On Wed, 2008-12-17 at 12:07 +0900, Fujii Masao wrote: > >> OK. I will extend synchronous_replication, make walsender send XLOG >> with synchronization mode flag and make walreceiver perform according >> to the flag. > > Sounds good. > >> > My perspective is that synchronous_replication specifies how long to >> > wait. Current settings are "off" (don't wait) or "on" (meaning wait >> > until point #3). So I think we should change this to a list of options >> > to allow people to more carefully select how much waiting is required. >> >> In the latest patch, "off" keeps us waiting for replication in some >> cases, e.g. forceSyncCommit = true. This is analogous to the way >> synchronous_commit works. When "off" keeps us waiting for >> replication, which option (#1-#6) should we choose? Should it be >> user-configurable (though the parameter values are doubled)? >> hardcode #3? "off" always should not keep us waiting for >> replication? > > I would hard code #4, i.e. make it fsync, so that DDL changes are > regarded as "high value transactions". > > A parameter sounds like overkill. We'd need to explain what > forceSyncCommit does to users then, which is easier to avoid. Agreed, I also think that hard code is better. But I'm nervous that "off" keeps us waiting for replication in cases other than DDL, e.g. flush buffer, truncate clog, checkpoint.. etc. synchronous_replication = off is quite similar to synchronous_commit = off. If we would hard code #4, the performance might degrade although it's asynchronous replication. So, I'd like to hard code #3. What is your opinion? Regards, -- Fujii Masao NIPPON TELEGRAPH AND TELEPHONE CORPORATION NTT Open Source Software Center -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
