Re: [RFC] Incremental backup v3: incremental PoC

Il 06/01/15 14:26, Robert Haas ha scritto:
> I suggest leaving this out altogether for the first version.  I can
> think of three possible ways that we can determine which blocks need
> to be backed up.  One, just read every block in the database and look
> at the LSN of each one.  Two, maintain a cache of LSN information on a
> per-segment (or smaller) basis, as you suggest here.  Three, scan the
> WAL generated since the incremental backup and summarize it into a
> list of blocks that need to be backed up.  This last idea could either
> be done when the backup is requested, or it could be done as the WAL
> is generated and used to populate the LSN cache.  In the long run, I
> think some variant of approach #3 is likely best, but in the short
> run, approach #1 (scan everything) is certainly easiest.  While it
> doesn't optimize I/O, it still gives you the benefit of reducing the
> amount of data that needs to be transferred and stored, and that's not
> nothing.  If we get that much working, we can improve things more
> later.
>

Hi,
The patch now uses the approach #1, but I've just sent a patch that uses
the #2 approach.

54AD016E.9020406@2ndquadrant.it

Regards,
Marco

--
Marco Nenciarini - 2ndQuadrant Italy
PostgreSQL Training, Services and Support
marco.nenciarini@2ndQuadrant.it | www.2ndQuadrant.it