[MAPSERVER-USERS] postgres transaction warnings

[rich.fromm]

I'm doing stress tests on a system with a java webapp running under tomcat,
using java mapscript and mapserver 5.0.0 (hand patched to fix mapserver bug
2525 (http://trac.osgeo.org/mapserver/ticket/2525)), fetching data from a
postgresql 8.1 / postgis 1.1.2 server.  In my postgres log file
(/var/log/postgresql/postgresql-8.1-main.log), I see a TON of messages like
the following:

2008-02-28 13:48:08 PST WARNING:  there is already a transaction in progress

The default value in the postgres configuration
(/etc/postgresql/8.1/main/postgresql.conf) for max_prepared_transactions is
only 5.  Based on the documentation here:

http://www.postgresql.org/docs/8.1/interactive/runtime-config-resource.html#RUNTIME-CONFIG-RESOURCE-MEMORY

I increased it substantially, so that it has the same value as
max_connections:

http://www.postgresql.org/docs/8.1/interactive/runtime-config-connection.html#GUC-MAX-CONNECTIONS

So now I would think that each connection to the database could
simultaneously
perform a transaction if so desired.  But I still get a TON of such
messages,
with no noticeable reduction.

This brings up a few questions:

1) In the mappostgis.c source, I see a number instances of transactions
   starting, via "BEGIN" statements.  There are also a number instances of
   transactions being canceled, via "ROLLBACK" statements, when something
goes
   wrong.  However, I can not find a single instance of a transaction being
   normally closed, via an "END" statement.  Is the code perhaps somehow
   leaking transaction resources?  Or maybe there's a genuine reason that
   "END" statements aren't needed?  Maybe something in some of the PQfoo()
   methods indirectly accounts for this?  I haven't looked at it in much
   detail, but I don't see anything in the libpq docs
   (http://www.postgresql.org/docs/8.1/static/libpq-exec.html) that suggests
   this.

2) In my situation, the database is effectively read only, because updates
   will happen infrequently and always in bulk and offline.  So I would
think
   that transactions are totally unnecessary, since any individual read
   statement will by definition see a consistent view of the database.
   Transactions aren't going to help at all, and would I think only serve to
   consume resources and possibly adversely affect performance.  I can see
how
   they might be needed in cases where updates were expected, but in my case
I
   would like to be able to disable them.  Is there any option to do this? 
I
   assume no.  But even if that is the case, is this analysis correct, and
   might such an option be a useful feature to provide?

So far this situation does not seem to be affecting correctness, and
performance is not unreasonable, but I wonder if performance might be better
if I could do something such that these WARNINGs were not present.

Thanks for any help that anyone might be able to provide.

- Rich

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