Re: About to add WAL write/fsync statistics to pg_stat_wal view

Hi, thanks for the reviews.

I updated the attached patch.
The summary of the changes is following.

1. fix document

I followed another view's comments.


2. refactor issue_xlog_fsync()

I removed "sync_called" variables, narrowed the "duration" scope and
change the switch statement to if statement.


3. make wal-receiver report WAL statistics

I add the code to collect the statistics for a written operation
in XLogWalRcvWrite() and to report stats in WalReceiverMain().

Since WalReceiverMain() can loop fast, to avoid loading stats collector,
I add "force" argument to the pgstat_send_wal function. If "force" is
false, it can skip reporting until at least 500 msec since it last 
reported. WalReceiverMain() almost calls pgstat_send_wal() with "force" 
as false.

Regards,
-- 
Masahiro Ikeda
NTT DATA CORPORATION