Re: Flush some statistics within running transactions

On 2026-Jan-30, Álvaro Herrera wrote:

> Interesting. Bertrand asked me about this. He says[1] he diagnosed this
> down to SetLatch being called immediately after the handler runs, and I
> wonder if it's correct that other timeout handler functions used for
> RegisterTimeout are doing SetLatch(). The SIGALRM handler
> handle_sig_alarm() that calls the specific handler function already has
> a SetLatch call, so why do we need another one here?

So apparently the first function to do this in postinit.c was added by
commit c6dda1f48e57 -- and apparently it was mimicking
CheckDeadLockAlert(), which at this time looked like this:

void
CheckDeadLockAlert(void)
{
int save_errno = errno;

got_deadlock_timeout = true;

/*
* Have to set the latch again, even if handle_sig_alarm already did. Back
* then got_deadlock_timeout wasn't yet set... It's unlikely that this
* ever would be a problem, but setting a set latch again is cheap.
*/
SetLatch(MyLatch);
errno = save_errno;
}

I wonder if it would work to move the SetLatch() that's currently at the
top of handle_sig_alarm() to the bottom, after we have called all the
specific handlers, and remove the ones that are there.

--
Álvaro Herrera 48°01'N 7°57'E — https://www.EnterpriseDB.com/