On 9/27/16 6:16 AM, Kyotaro HORIGUCHI wrote:

I apologize in advance that the comments in this message might
one of the ideas discarded in the past thread.. I might not grasp
the discussion completely X(

The attached patches are rebased to the master and additional one
mentioned below.

I tried the attached patch set and noticed an interesting behavior. With archive_timeout=5 whenever I made a change I would get a WAL segment within a few seconds as expected then another one would follow a few minutes later.

Database init:
16M Sep 27 20:05 000000010000000000000001
16M Sep 27 20:09 000000010000000000000002

Create test table:
16M Sep 27 20:13 000000010000000000000003
16M Sep 27 20:15 000000010000000000000004

Insert row into test table:
16M Sep 27 20:46 000000010000000000000005
16M Sep 27 20:49 000000010000000000000006

The cluster was completely idle with no sessions connected in between those three commands. Is it possible this is caused by:

+                * switch segment only when any substantial progress have made 
from
+                * the last segment switching by timeout. Segment switching by 
other
+                * reasons will cause last_xlog_switch_lsn stay behind but it 
doesn't
+                * matter since it just causes possible one excessive segment 
switch.
                 */

I would like to give Michael a chance to respond to the updated patches before delving deeper.

--
-David
da...@pgmasters.net


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