Re: On login trigger: take three

Hi!

On Tue, Oct 3, 2023 at 8:35 PM Alexander Korotkov <aekorotkov@gmail.com> wrote:
> Thank you for the interesting ideas. I'd like to try to revive the
> version with the flag in pg_database.  Will use other ideas as backup
> if no success.

I've revived the patch version with pg_database.dathasloginevt flag.
I took v32 version [1] and made the following changes.

 * Incorporate enchantments made on flagless version of patch.
 * Read dathasloginevt during InitPostgres() to prevent extra catalog
access and even more notable StartTransactionCommand() when there are
no login triggers.
 * Hold lock during setting of pg_database.dathasloginevt flag (v32
version actually didn't prevent race condition).
 * Fix AlterEventTrigger() to check event name not trigger name
 * Acquire conditional lock while resetting pg_database.dathasloginevt
flag to prevent new database connection to hang waiting another
transaction to finish.

This version should be good and has no overhead.  Any thoughts?
Daniel, could you please re-run the performance tests?

Links
1. https://www.postgresql.org/message-id/CAMEv5_vDjceLr54WUCNPPVsJs8WBWWsRW826VppNEFoLC1LAEw%40mail.gmail.com

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Regards,
Alexander Korotkov