On Fri, May 22, 2015 at 11:20 PM, Andres Freund <and...@anarazel.de> wrote: > > On 2015-05-21 09:40:58 +0530, Amit Kapila wrote: > > On Thu, May 21, 2015 at 12:42 AM, Andres Freund <and...@anarazel.de> wrote: > > > > > > On 2015-05-20 19:27:05 +0530, Amit Kapila wrote: > > > > > > > 13. > > > > In function replorigin_session_setup() and or > > > > replorigin_session_advance(), don't we need to WAL log the > > > > use of Replication state? > > > > > > No, the point is that the replication progress is persisted via an extra > > > data block in the commit record. That's important for both performance > > > and correctness, because otherwise it gets hard to tie a transaction > > > made during replay with the update to the progress. Unless you use 2PC > > > which isn't really an alternative. > > > > > > > Okay, but what triggered this question was the difference of those functions > > as compare to when user call function pg_replication_origin_advance(). > > pg_replication_origin_advance() will WAL log the information during that > > function call itself (via replorigin_advance()). So even if the transaction > > issuing pg_replication_origin_advance() function will abort, it will still > > update > > the Replication State, why so? > > I don't see a problem here. pg_replication_origin_advance() is for > setting up the initial position/update the position upon configuration > changes.
Okay, I am not aware how exactly these API's will be used for replication but let me try to clarify what I have in mind related to this API usage. Can we use pg_replication_origin_advance() for node where Replay has to happen, if Yes, then Let us say user of pg_replication_origin_advance() API set the lsn position to X for the node N1 on which replay has to happen, so now replay will proceed from X + 1 even though the information related to X is not persisted, so now it could so happen X will get written after the replay of X + 1 which might lead to problem after crash recovery? > It'd be a fair amount of infrastructure to make it tie into > transactions - without a point to it afaics? > Agreed, that if there is no valid use case then we should keep it as it is. > (Just to be clear, I plan to address all the points I've not commented > upon) > Thanks. With Regards, Amit Kapila. EnterpriseDB: http://www.enterprisedb.com
