Fujii Masao wrote: > On Mon, Sep 8, 2008 at 8:44 PM, Markus Wanner <[EMAIL PROTECTED]> wrote: > >> Merge into WAL writer? > > > > Uh.. that would mean you'd loose parallelism between WAL writing to disk and > > WAL shipping via network. That does not sound appealing to me. > > That depends on the order of WAL writing and WAL shipping. > How about the following order? > > 1. A backend writes WAL to disk. > 2. The backend wakes up WAL sender process and sleeps. > 3. WAL sender process does WAL shipping and wakes up the backend. > 4. The backend issues sync command.
I am confused why this is considered so complicated. Having individual backends doing the wal transfer to the slave is never going to work well. I figured we would have a single WAL streamer that continues advancing forward in the WAL file, streaming to the standby. Backends would update a shared memory variable specifying how far they want the wal streamer to advance and send a signal to the wal streamer if necessary. Backends would monitor another shared memory variable that specifies how far the wal streamer has advanced. -- Bruce Momjian <[EMAIL PROTECTED]> http://momjian.us EnterpriseDB http://enterprisedb.com + If your life is a hard drive, Christ can be your backup. + -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
