Tom Lane wrote:
Heikki Linnakangas <[EMAIL PROTECTED]> writes:
We could just allow any value up to 1.0, and note in the docs that you should leave some headroom, unless you don't mind starting the next checkpoint a bit late. That actually sounds pretty good.


Yeah, that sounds fine.  There isn't actually any harm in starting a
checkpoint later than otherwise expected, is there?  The worst
consequence I can think of is a backend having to take time to
manufacture a new xlog segment, because we didn't finish a checkpoint
in time to recycle old ones.  This might be better handled by allowing
a bit more slop in the number of recycled-into-the-future xlog segments.

Come to think of it, shouldn't we be allowing some extra slop in the
number of future segments to account for xlog archiving delays, when
that's enabled?

XLogFileSlop is currently 2 * checkpoint_segments + 1 since last checkpoint, which is just enough to accommodate a checkpoint that lasts the full checkpoint interval. If we want to keep as much "slop" there as before, then yes that should be increased to (2 + checkpoint_completion_target) * checkpoint_segments + 1, or just 3 * checkpoint_segments if we want to keep it simple.

--
  Heikki Linnakangas
  EnterpriseDB   http://www.enterprisedb.com

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