Re: DISCARD ALL (Again)

On Fri, Apr 18, 2014 at 2:24 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> 2. While I'm no Python expert, I believe GD is just a specific instance
> of a general capability for global state in Python.  Are we going to
> promise that any and all user-created data inside Python goes away?
> What about other PLs?  Will users thank us if this suddenly starts
> happening?

This is not the first time that somebody's asked for a way to throw
away global interpreter state, and I really think we ought to oblige.
In a connection-pooling environment, you really need a way to get the
connection back to its original state rather than some not-so-near
facsimile thereof.  Maybe it'll end up as an optional behavior, and
which kind of reset to use will become part of the pooler
configuration, but that doesn't bother me as much as not having it for
those that want it.

What's a bit odd about this request is that it asks for the ability to
throw away only part of the state.  ISTM that if somebody wants to add
that kind of capability, they ought to just package a function which
does precisely that with the plpython extension, or create a Python
function that zaps that particular variable if that's possible.  I
think it's clearly useful to have DISCARD ALL be a request to discard
*everything* in one shot, but it's going to be a stretch to come up
with DISCARD variants for every kind of partial state removal somebody
wants to do.

-- 
Robert Haas
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