On 19 June 2012 14:03, Tom Lane <t...@sss.pgh.pa.us> wrote: > "Every WAL record"? Why in heck would you attach it to every record? > Surely putting it in WAL page headers would be sufficient. We could > easily afford to burn a page switch (if not a whole segment switch) > when changing masters.
This does appear to be a reasonable idea at first glance, since it seems that each node has just a single node id, but that is not the case. As we pass changes around we maintain the same origin id for a change, so there is a mix of origin node ids at the WAL record level, not the page level. The concept of originating node id is essentially same as that used in Slony. > I'm against the idea of eating any spare space we have in WAL record > headers for this purpose, anyway; there are likely to be more pressing > needs in future. Not sure what those pressing needs are, but I can't see any. What we are doing here is fairly important, just not as important as crash recovery. But then that has worked pretty much unchanged for some time now. I raised the possibility of having variable length headers, but there is no requirement for that yet. -- 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
