Hi Paul, Thanks for the quick explanation of replication. I am starting to recommend that our customers look at PBXT as a possible substitute for InnoDB; this seems like one more reason.
For Jay and my upcoming talk we will definitely discuss physical replication approaches. We may need to run some information past you to ensure we give PBXT accurate credit. Cheers, Robert On 3/24/10 1:11 AM PDT, "Paul McCullagh" <paul.mccull...@primebase.org> wrote: >> >> This is a very interesting point. Physical and logical replication >> are kind >> of like Yin and Yang for building systems. >> >> I was thinking of pointing out in the talk the work going on in >> PostgreSQL >> with PG 9 and streaming replication/hot standby. The PostgreSQL >> approach, >> as you are probably aware, has been to implement very solid physical >> replication while leaving logical replication to external, trigger- >> based >> products like Londiste. > > This is basically the PBXT approach. > >> How do you get around some of the issues like snapshot maintenance for >> queries that are currently consuming cycles in the PostgreSQL >> effort? In >> the current PG 9 alpha users may have to choose between between up >> to date >> slaves and ability to run queries that maintain a snapshot for a >> lengthy >> period of time. > > Should not be much of a problem because PBXT MVCC implementation can > handle long running snapshot queries/transactions. PBXT stores all > versions of a row on disk, so it does not limit the size of a snapshot. > > However, each version of a row is indexed. So a long running snapshot > can lead to inflation of the index. This is not a problem for updates, > however. Especially not replicated updates which are based on the > internal row ID. So a snapshot should not have that much affect on the > speed at which replication changes are applied. > > But, it can affect the speed of long running SELECTs that are being > done on the slave. > > Best regards, > > Paul _______________________________________________ Mailing list: https://launchpad.net/~drizzle-discuss Post to : drizzle-discuss@lists.launchpad.net Unsubscribe : https://launchpad.net/~drizzle-discuss More help : https://help.launchpad.net/ListHelp
