[MAPSERVER-USERS] postgres transaction warnings

[rich.fromm]

rich.fromm wrote:
> 
> 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
> 
> <...>
> 
> 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?
> 

Did some more looking around on my own.  Regarding (1), something similar
seems to have been reported previously on the old mailing list:

http://www.nabble.com/Segmentation-fault---mapserver---postgis-to12653945.html#a12674499

I think bug 2497 is at least partially addressing this:

http://trac.osgeo.org/mapserver/ticket/2497

I can try locally applying the diff there, but I'm still a bit confused. 
Just moving the BEGIN and not inserting an END may solve a problem of
unnecessary duplicate transactions, but I still don't understand how the
transaction gets properly ended.

Oh yeah, I do have for each LAYER:
   PROCESSING	"CLOSE_CONNECTION=DEFER"

I haven't found anything yet addresing (2).

- Rich

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