Thanks for responding. On Wed, Aug 14, 2024 at 10:29 PM Nathan Bossart <nathandboss...@gmail.com> wrote:
> On Thu, Jul 25, 2024 at 11:13:39AM +0800, SAMEER KUMAR wrote: > > While preparing for my presentation on PostgreSQL Wait Events at > > PgConf India, I was trying to understand *IPC:XactGroupUpdate* in more > > detail. PostgreSQL documentation [1] mentions: > > > >> A process is waiting for the group leader to update the transaction > status at the end of a _parallel operation_. > > > > I looked at `TransactionGroupUpdateXidStatus` in PostgreSQL code > (`clog.c`) > > Line `481` [2] sets this wait event. > > > > And after reading the code, my understanding is - It does not > > necessarily need to be a "_parallel operation_". Or maybe I am just > > misinterpreting "parallel operation" in this context. But it is > > possible for other users to confuse it with the parallel query (and > > parallel workers) feature. > > > > [...] > > > > We can add more clarity on what this wait event means. A similar > > change should be done for `ProcArrayGroupUpdate` to indicate that the > > wait event is a result of concurrent backend processes trying to clear > > the transaction id (instead of saying "parallel operation"). > > Both of these wait events had descriptions similar to what you are > proposing when they were first introduced (commits d4116a7 and baaf272), > but they were changed to the current wording by commit 3048898. I skimmed > through the thread for the latter commit [0] but didn't see anything that > explained why it was changed. > Yes, while reviewing the history of changes, I too noticed the same. The documentation of older versions (v12 [1]) still has old descriptions. > > [0] https://postgr.es/m/21247.1589296570%40sss.pgh.pa.us > > -- > nathan > [1] https://www.postgresql.org/docs/12/monitoring-stats.html#WAIT-EVENT-TABLE
