On Tue, 2010-04-27 at 09:50 -0400, Alvaro Herrera wrote: > Simon Riggs wrote: > > > > Thinking about allowing a backup to tell which files have changed in the > > database since last backup. This would allow an external utility to copy > > away only changed files. > > > > Now there's a few ways of doing this and many will say this is already > > possible using file access times. > > > > An explicit mechanism where Postgres could authoritatively say which > > files have changed would make many feel safer, especially when other > > databases also do this. > > > > We keep track of which files require fsync(), so we could also keep > > track of changed files using that same information. > > Why file level? Seems a bit too coarse (particularly if you have large > file support enabled). Maybe we could keep block-level last change info > in a separate fork.
Block-level is mostly available by using LSN, you just need to scan the file. So block level seems not useful enough for the extra overhead. File-level would be sufficient for most purposes. If you wanted to go finer grained you can then scan just the files that have changed. -- Simon Riggs www.2ndQuadrant.com -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
