If synchronous_commit is enabled, transaction commit will wait for WAL records to be written to disk before the command returns a "success" indication to the client. Shared buffers is not involved when commit is issued. For flushing of shared buffers to data files, we can use checkpoint instead. BGWR in charge of writing shared_buffers to the datafiles.
Thanks!
On 28 January 2016 at 19:49, Jürgen Purtz <juergen@purtz.de> wrote:
Hi,
can anyone explain, what happens first during an UPDATE of an indexed column: writing and flushing to WAL or modification of shared buffers? And: both actions are finished before a confirmation is send to the requesting client - or?
