From: | Alvaro Herrera <alvherre(at)commandprompt(dot)com> |
---|---|
To: | Luca Ferrari <fluca1978(at)infinito(dot)it> |
Cc: | pgsql-general <pgsql-general(at)postgresql(dot)org> |
Subject: | Re: what is the meaning of Datum? |
Date: | 2010-06-23 16:15:06 |
Message-ID: | 1277309663-sup-9263@alvh.no-ip.org |
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Thread: | |
Lists: | pgsql-general |
Excerpts from Luca Ferrari's message of mié jun 23 06:09:28 -0400 2010:
> Hi all,
> ok this is a silly question, but I've got a doubt: what is the exact meaning
> of Datum? I see having a look at the macroes (e.g., PG_RETURN_XXX) that a
> Datum can be used as a pointer or as a single data, that is it can be a
> reference or a value. Is this right?
Yes
> So for instance the fact that each stored
> procedure returns a Datum means that the semantic of the Datum is interpreted
> depending on how the procedure is defined in the SQL language (i.e., it returns
> a integer, a tuple, ...). Am I right?
Yes
> Moreover, is there a documentation (aside the source code) that explains and
> links each internal data structure like HeapTuple, HeapTupleHeader, and so on?
The source code comments should be plenty. Have you tried reading
those?
--
Álvaro Herrera <alvherre(at)commandprompt(dot)com>
The PostgreSQL Company - Command Prompt, Inc.
PostgreSQL Replication, Consulting, Custom Development, 24x7 support
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