On Wed, 2005-04-20 at 15:51 -0400, Tom Lane wrote: > Simon Riggs <[EMAIL PROTECTED]> writes: > > AFAICS this is the only case of unconditionally acquiring all 3 locks. > > You just lost me ... I think the above is certainly a bad idea from a > concurrency standpoint, and very possibly a deadlock risk.
'twas my fear too. > In any case you are thinking about it the wrong way. It is not > LogwrtResult you want to advance, it is the Insert variables that define > what the current WAL buffer page is. Yes OK, so that way I don't need the 3 locks. Good. > ISTM the correct approach involves having a special case in XLogInsert: > just after inserting an end-of-file record, forcibly advance to the next > buffer, and set it up to be the first page for the next segment rather > than the next segment in sequence. (This is likely best handled as an > extra call to AdvanceXLInsertBuffer that invokes some special-case code > in AdvanceXLInsertBuffer.) You normally only need the WALInsertLock to > do this. After that's complete you can release the insert lock, and > then other operations can proceed while you do an XLogFlush to force out > the remaining dirty WAL buffers for the old segment. Then you're done. Good. Thats was roughly what I'm attempting now, just advancing the wrong pointer and struggling/worried by the 3 lock problem. > (I think I'd put the XLogFlush in the pg_stop_backup code, not in > XLogInsert proper.) That seems like the way its done elsewhere. Best Regards, Simon Riggs ---------------------------(end of broadcast)--------------------------- TIP 8: explain analyze is your friend
