Re: [PATCHES] WIP: executor_hook for pg_stat_statements

ITAGAKI Takahiro <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp> writes:
> Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
>>> Also, after looking at the patch more closely, was there a good reason
>>> for making the hook intercept ExecutePlan rather than ExecutorRun?
>>
>> That raises the question of whether we should have ExecutorStart() and
>> ExecutorEnd() hooks as well, to round things off.

> Yeah, and also ExecutorRewind() hook.

I'm not impressed by this line of argument. If we start putting in
hooks just because someone might need 'em someday, we'd soon end up with
hundreds or thousands of mostly-useless hooks. I'm happy to put in
hooks that there's a demonstrated need for, but I don't believe that
"replace the executor without touching the core code" is a sane goal.
Even if it were, the API of the executor to the rest of the system
is a whole lot wider than four functions.

regards, tom lane