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Re: Data transfer very slow when connected via DSL

From: Dimitri <dimitrik(dot)fr(at)gmail(dot)com>
To: "Rainer Bauer" <usenet(at)munnin(dot)com>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Data transfer very slow when connected via DSL
Date: 2007-06-21 22:38:40
Message-ID: 5482c80a0706211538ka531c18gcf681cd5a68066b2@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-performance
Let's stay optimist - at least now you know the main source of your problem! :))

Let's see now with CURSOR...

Firstly try this:
munnin=>\timing
munnin=>\set FETCH_COUNT 1;
munnin=>select * from "tblItem";

what's the time you see here? (I think your application is working in
this manner)

Now, change the FETCH_COUNT to 10, then 50, then 100 - your query
execution time should be better (at least I hope so :))

And if it's better - you simply need to modify your FETCH clause with
adapted "FORWARD #" value (the best example is psql source code
itself, you may find ExecQueryUsingCursor function implementation
(file common.c))...

Rgds,
-Dimitri

On 6/22/07, Rainer Bauer <usenet(at)munnin(dot)com> wrote:
> Hello Dimitri,
>
> >but did you try to execute your query directly from 'psql' ?...
>
> munnin=>\timing
> munnin=>select * from "tblItem";
> <data snipped>
> (50 rows)
> Time: 391,000 ms
>
> >Why I'm asking: seems to me your case is probably just network latency
> >dependent, and what I noticed during last benchmarks with PostgreSQL
> >the SELECT query become very traffic hungry if you are using CURSOR.
> >Program 'psql' is implemented to not use CURSOR by default, so it'll
> >be easy to check if you're meeting this issue or not just by executing
> >your query remotely from 'psql'...
>
> Yes, see also my other post.
>
> Unfortunatelly this means that using my program to connect via DSL to the
> Postgres database is not possible.
>
> Rainer
>
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