On Sun, Apr 4, 2021, at 09:16, Fabien COELHO wrote:
If other cases are indeed pointers. For pgbench, all direct "if (xxx &&"
cases are simple booleans or integers, pointers seem to have "!= NULL".
While looking quickly at the grep output, ISTM that most obvious pointers
have "!= NULL" and other cases often look like booleans:
catalog/pg_operator.c: if (isDelete && t->oprcom == baseId)
catalog/toasting.c: if (check && lockmode != AccessExclusiveLock)
commands/async.c: if (amRegisteredListener && listenChannels == NIL)
commands/explain.c: if (es->analyze && es->timing)
…
I'm sure there are exceptions, but ISTM that the local style is "!= NULL".
Many thanks for explaining.
>> I'm wondering whether it should be possible to designate (1) a file the
>> content of which would be shown, or (2) a command, the output of which
>> would be shown [ok, there might be security implications on this one].
>
> Can't we just do that via plpgsql and EXECUTE somehow?
Hmmm.
Should we want to execute forcibly some PL/pgSQL on any new connection?
Oh, of course, you want the command to be execute for each new connection.
My idea was to use PL/pgSQL to execute only when you wanted to update the stored motd value,
but of course, if you want a new value from the command for each new connection,
then that doesn't work (and it doesn't work anyway due to not being able to execute ALTER SYSTEM from functions).
Not sure this is really desirable. I was thinking of something more
trivial, like the "motd" directeve could designate a file instead of the
message itself.
There could be a hook system to execute some user code on new connections
and other events. It could be a new kind of event trigger, eg with
connection_start, connection_end… That could be nice for other purposes,
i.e. auditing. Now, event triggers are not global, they work inside a
database, which would suggest that if extended a new connection event
would be fired per database connection, not just once per connection. Not
sure it would be a bad thing.
Such a hook sounds like a good idea.
If we would have such a hook, then another possibility would be to implement motd as an extension, right?
/Joel
