On Wed, Jul 28, 2010 at 3:16 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: > (1) You're assuming that the page will be zeroes on the slave without > having forced it to be so. A really obvious case where this fails > is where we're doing crash-and-restart on the master: a later action > could have modified the page away from the all-zero state. (In > principle that's OK but I think this might break torn-page protection.)
Hmm, yeah, that does seem like it has the potential to be bad. I think this is sufficient reason to go with fix #1. > (2) On filesystems that support holes, the page will not have storage, > whereas it (probably) does on the master. This could lead to a > divergence in behavior later, ie slave runs out of disk space at a > different point than the master. I can't get excited about this one. > (3) The position of the nominal EOF can drive choices about which page > to put new tuples in, specifically thats where RelationGetBufferForTuple > will go if FSM has no information. This could result in unexpected > divergence in behavior after the slave goes live compared to what the > master would have done. Maybe that's OK but it seems better to avoid > it if we can, especially when you think about crash-and-restart on the > master as opposed to a separate slave. You're still going to have that in the "normal" (not altering the tablespace) extension case, which is presumably far more common. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise Postgres Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
