On 01/03/2015 12:28 AM, Josh Berkus wrote:
On 01/02/2015 01:57 AM, Heikki Linnakangas wrote:
wal_keep_segments does not affect the calculation of CheckPointSegments.
If you set wal_keep_segments high enough, checkpoint_wal_size will be
exceeded. The other alternative would be to force a checkpoint earlier,
i.e. lower CheckPointSegments, so that checkpoint_wal_size would be
honored. However, if you set wal_keep_segments high enough, higher than
checkpoint_wal_size, it's impossible to honor checkpoint_wal_size no
matter how frequently you checkpoint.

So you're saying that wal_keep_segments is part of the max_wal_size
total, NOT in addition to it?

Not sure what you mean. wal_keep_segments is an extra control that can prevent WAL segments from being recycled. It has the same effect as archive_command failing for N most recent segments, if that helps.

Just asking for clarification, here.  I think that's a fine idea, I just
want to make sure I understood you.  The importance of wal_keep_segments
will be fading as more people use replication slots.


- Heikki

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