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Subject: [Pljava-dev] VarLenTuple example code
Date: Fri, 29 Sep 2006 15:37:28 +0200
Message-ID: <451D2198.7050202@logix-tt.com> (raw)
In-Reply-To: <451D10E0.8020003@tada.se>
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Hi, Thomas,

Thomas Hallgren wrote:

>> But C is the one that's stored on disk by PostgreSQL, neither D nor B.
> Now I'm confused. I though you said C was the internal representation?

Yes, as I described it in Message-ID: <45183343.8000105 at logix-tt.com>
rsp. http://gborg.postgresql.org/pipermail/pljava-dev/2006/000925.html -
at least that's how I thought things work in PostgreSQL:

> C) is what PostgreSQL passes around (to PostGIS C functions as well as
> to the PLJava glue code), and stores on disk. The size is defined as
                            ^^^^^^^^^^^^^^^^^^
> "internallength" in the datatype, and contained in a 4-byte VARLEN
> header for variable length datatypes which have internallength set to
> -1. (let's ignore TOAST and 0-terminated Strings for simplification.)

It's "internal" in the sense that it is not visible to clients outside
of the Postmaster.

Clients (including pg_dump/pg_restore and the COPY formats) see what
output/input (A) and send/receive (B) produce and consume, depending on
whether they use text and binary mode.

But as far as I can tell, PostgreSQL does not use send/receive before
writing the tuple data on disk. At least that is what I believed so far,
I'm rather irritated now and I'm going to double- and triple-check that
immediately.

Thanks,
Markus

-- 
Markus Schaber | Logical Tracking&Tracing International AG
Dipl. Inf.     | Software Development GIS

Fight against software patents in Europe! www.ffii.org
www.nosoftwarepatents.org

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