On Mon, Aug 15, 2011 at 10:32 PM, Magnus Hagander <mag...@hagander.net> wrote:
>> At present the WALSender only sends from one file at a time, so >> sending a message when we open a new file would be straightforward. > > Are you sure? We can receive a single message spanning multiple files... You're right. That was the way the original code ran but I thought we had stopped that when we introduced MAX_SEND_SIZE. The comment says "don't cross a logfile boundary within one message". What that actually does is prevent us incrementing a logid value, which happens every 255 files. I read that as meaning "WAL file" which is not what it means at all. So right now what we do is allow a single packet to span multiple files, but since MAX_SEND_SIZE is 128KB it will always be smaller than a single file, so we can only ever span two files at most. That is all just a little bizarre, especially since libpq sends data in 8KB chunks anyway. So I suggest we change XLogSend() so that it only ever sends up to the end of a file. That way all "w" messages will relate to just one file, and we can have another message to initiate a new file. And then, as you say, give full metadata for the new file. -- Simon Riggs http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
