> Tatsuo>Interesting. What would happen if a user changes some of GUC
> parameters? Subsequent session accidentally inherits the changed GUC
> parameter?
> Yes, that is what happens.


> The idea is not to mess with gucs.
> Tatsuo>There's nothing wrong with DICARD ALL
> Tatsuo>"DISCARD ALL" is perfect for this goal.
> It looks like you mean: "let's reset the connection state just in case".
> I see where it might help: e.g. when providing database access to random
> people who might screw a connection in every possible way.

Yes, that's what clients of pgpool is expecting. Clients do not want
to change their applications which were working with PostgreSQL
without pgpool.

> Just in case: do you think one should reset CPU caches, OS filesystem
> caches, DNS caches, bounce the application, and bounce the OS in addition
> to "discard all"?

Aparently no, because that is different from what PostgreSQL is doing
when backend exits.

> Why reset only "connection properties" when we can reset everything to its
> pristine state?

You can propose that kind of variants of DISCARD command. PostgreSQL
is an open source project.

> Just in case: PostgreSQL does not execute "discard all" on its own.
> If you mean "pgpool is exactly like reconnect to postgresql but faster
> since connection is already established", then OK, that might work in some
> cases (e.g. when response times/throughput are not important), however why
> forcing "you must always start from scratch" execution model?

I'm not doing that. I do not ask all the people to use pgpool. People
can choose whatever tools he/she thinks suitable for their purpose.

> Developers are not that dumb, and they can understand that "changing gucs
> at random is bad".
> When a connection pool is dedicated to a particular application (or a set
> of applications), then it makes sense to reuse statement cache for
> performance reasons.
> Of course, it requires some discipline like "don't mess with gucs", however
> that is acceptable and it is easily understandable by developers.

I'm not against such a developer's way. If you like it, you can do
it. Nobody disturbs you. I just want to say that not all the client
want that way.

Best regards,
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php

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