On Thursday, June 14, 2012 11:19:00 PM Heikki Linnakangas wrote: > On 13.06.2012 14:28, Andres Freund wrote: > > Features: > > - streaming reading/writing > > - filtering > > - reassembly of records > > > > Reusing the ReadRecord infrastructure in situations where the code that > > wants to do so is not tightly integrated into xlog.c is rather hard and > > would require changes to rather integral parts of the recovery code > > which doesn't seem to be a good idea. > > It would be nice refactor ReadRecord and its subroutines out of xlog.c. > That file has grown over the years to be really huge, and separating the > code to read WAL sounds like it should be a pretty natural split. I > don't want to duplicate all the WAL reading code, so we really should > find a way to reuse that. I'd suggest rewriting ReadRecord into a thin > wrapper that just calls the new xlogreader code. > > > Missing: > > - "compressing" the stream when removing uninteresting records > > - writing out correct CRCs > > - validating CRCs > > - separating reader/writer > > - comments. > > At a quick glance, I couldn't figure out how this works. There seems to > be some callback functions? If you want to read an xlog stream using > this facility, what do you do? Can this be used for writing WAL, as well > as reading? If so, what do you need the write support for? Oh, btw, the callbacks and parameters are somewhat documented in the xlogreader.h header in the XLogReaderState struct. Still needs improvement though.
Andres -- Andres Freund 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
