why we need both the collector & buffer process

=?gb2312?q?William.Jiang?= wrote:

hi,all hackers of postgres

when postmaster start as a service . another two
processes(collector & buffer ) start their work at the same
time.

I have read the code and I am wondering why we need two
processes to do the work. I think one process can work as
well. Are there something special you considered when you
developed this feature?

One collects statistics for the pg_stat tables, and the other does
checkpoints. They are different functions.

--
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

"=?gb2312?q?William.Jiang?=" <jiang_sir@yahoo.com.cn> writes:

I have read the code and I am wondering why we need two processes to do the work. I think one process can work as well. Are there something special you considered when you developed this feature?

It's a buffering issue. Read the discussion in the pghackers archives
for details.

regards, tom lane

Sorry to say that I cannot see which process is used to do checkpoints. I just see two main functions.
pgstat_recvbuffer(): this function is to receive the information from the postgres .this function is the main body of buffer process
pgstat_min():this function is to do the job of getting information from the buffer process and writing them to the file . and this is the main body of collector process.
Any function else to do the checkpoint job?
Best Wishes!
William
Bruce Momjian <pgman@candle.pha.pa.us> wrote:
=?gb2312?q?William.Jiang?= wrote:

hi,all hackers of postgres

when postmaster start as a service . another two
processes(collector & buffer ) start their work at the same
time.

I have read the code and I am wondering why we need two
processes to do the work. I think one process can work as
well. Are there something special you considered when you
developed this feature?

One collects statistics for the pg_stat tables, and the other does
checkpoints. They are different functions.

--
Bruce Momjian | http://candle.pha.pa.us
pgman@candle.pha.pa.us | (610) 359-1001
+ If your life is a hard drive, | 13 Roberts Road
+ Christ can be your backup. | Newtown Square, Pennsylvania 19073

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