On 28 Feb 2014 06:19, "Andres Freund" <and...@2ndquadrant.com> wrote: > > On 2014-02-27 23:41:08 +0000, Greg Stark wrote: > > Though I notice something I can't understand here. > > > > After activating the new clone subsequent attempts to select rows from > > the page bump the LSN, presumably due to touching hint bits (since the > > prune xid hasn't changed). But the checksum hasn't changed even after > > running CHECKPOINT. > > Are you running with full_page_writes=off?
No > Only delete and update do a PageSetPrunable(), so prune_xid not being > changed doesn't say much... > > > How is it possible for the LSN to get updated without changing the checksum? > > Generally the LSN is computed when writing, not when a buffer is > modified, so that's not particularly surprising. It'd be interesting to > see what the records are that end on those LSNs. The checksum you mean? But that's why I ran checkpoint. > It'd probably nice to add the capability to dump records that end in a > particular location to pg_xlogdump... I have this crazy idea about combining xlogdump and pg_receivexlog to archive all xlog to a postgres database for querying.....
