Re: PHP and PostgreSQL

This is interesting. I always wondered how the persistent connection
stuff handled this, and not I see that it doesn't.

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> > The only problem we have run into (and I have heard of others having this
> > problem also) is with persistent connections. I have seen discussion on
> > persistent connection problems but I'm not sure the problem was ever
> > resolved. The problem we have seen is that when using persistent
> > connections the web server doesn't seen to reuse the connections or
> somthing
> > to that effect. The result being that we eventually use up our postgres
> > limit of 48 connections and nothing can connect to postgre anymore. It is
> > possible that this is a configuration problem that we haven't sufficiently
> > investigated, but I meniton it because I have heard other talk of this.
> > Anyone have more information?
>
> The *real* problem with persistent connections is:
>
> Script1: BEGIN;
> Script1: UPDATE table set row = 'things';
> Script2: Insert into table (id) values ('bad data');
> Script1: COMMIT;
>
> Since script2 managed to do a BAD insert in the middle of script1's
> transaction, the transaction in script1 fails. Obvious solution? Don't do
> connection sharing when a transaction is enabled. The whole persistent
> connection thing is only valid for mysql as it's the only thing that doesn't
> really support transactions (and even thats partially changed).
>
> They need to look for stuff going through (keywords like BEGIN) and 'lock'
> that connection to the single entity that opened it.
>
> It's much easier to write your own. I wrote a few functions like:
>
> get_connection('DB PARMS');
> begin_transaction();
>
> commit_transaction();
> close_connection();
>
> All of this is done in a class which has knowledge of all connections that a
> script is currently using. Beginning a transaction locks down the
> connection from use by any other handler, they're all bumped to another one.
> Problem? It requires atleast 1 connection per page, but since they're
> actually dropped at close it's not so bad.
>
>

--
Bruce Momjian | http://candle.pha.pa.us
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