Andres Freund <andres(at)anarazel(dot)de> writes:
> I'm not entirely sure what
> + /*
> + * Caution: do not call pg_flush_data with amount = 0, it could trash the
> + * file's seek position.
> + */
> + if (amount <= 0)
> + return;
> +
> is about?
fd.c tracks seek position for open files. I'm not sure that that
function can get called with amount == 0, but if it did, the caller
would certainly not be expecting the file position to change.
regards, tom lane