Re: Protocol 3, Execute, maxrows to return, impact?

From: Gregory Stark <stark(at)enterprisedb(dot)com>
To: "Abhijit Menon-Sen" <ams(at)oryx(dot)com>
Cc: "Stephen R(dot) van den Berg" <srb(at)cuci(dot)nl>, <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Protocol 3, Execute, maxrows to return, impact?
Date: 2008-07-10 18:01:04
Message-ID: 87vdzdbov3.fsf@oxford.xeocode.com
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"Abhijit Menon-Sen" <ams(at)oryx(dot)com> writes:

>> Interleaved retrieval using multiple portals is not what most
>> libraries support, I'd guess.
>
> My code did support that mode of operation in theory, but in practice
> in the few situations where I have needed to use something like it, I
> found it more convenient to open explicit cursors and FETCH from them

Note that using FETCH for each record means a round trip to the server for
each record. If you're dealing with a lot of records that could be a lot
slower than streaming them to the client as quickly as it can consume them.

Now I'm not sure anyone's actually done any experiments to optimize libpq or
other drivers to stream data efficiently, so I'm not sure how much you would
really lose in practice today.

--
Gregory Stark
EnterpriseDB http://www.enterprisedb.com
Ask me about EnterpriseDB's On-Demand Production Tuning

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