On Sat, Feb 12, 2011 at 11:32 PM, Robert Haas <robertmh...@gmail.com> wrote: > So, what if we did some renaming? I'd be inclined to start by > renaming "receivedUpTo" to Flush, and add a new position called > Stream. When walreciever is started, we set Stream to the position at > which streaming is going to begin (which can rewind) and leave Flush > alone (so it never rewinds). We then change the walreceiver feedback > mechanism to use the term stream_location rather than write_location; > and we could consider replacing pg_last_xlog_receive_location() with > pg_last_xlog_stream_location() and pg_last_xlog_flush_location().
You suggest that the shared variable Stream tracks the WAL write location, after it's set to the replication starting position? I don't think that the write location needs to be tracked in the shmem because other processes than walreceiver don't use it. What I proposed is: Walreceiver-local variables ================== 1. LogstreamResult.Write - Indicates the location of recently written WAL record - Can rewind - pg_stat_replication.write_location returns this 2. LogstreamResult.Flush - Indicates the location of recently flushed WAL record - Can rewind - pg_stat_replication.flush_location returns this Shmem variables =========== 3. WalRcv->receiveStart - Indicates the replication starting location - Updated only when walreceiver is started - Doesn't exist at the moment, so I propose to add this 4. WalRcv->receivedUpto - Indicates the latest location of all the flushed WAL records - Never rewinds (Can rewind at the moment, so I propose to prevent the rewind) - pg_last_xlog_receive_location returns this You propose to rename LogstreamResult.Write to .Stream, and merge it and receiveStart? > I'd also be inclined to go to the walreceiver code and and rename the > apply_location to replay_location, so that it matches > pg_last_xlog_replay_location(). The latter is in 9.0, but the former > is new to 9.1, so we can still fix it to be consistent without a > backward compatibility break. +1 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