From: Bruce Momjian <maillist@candle.pha.pa.us>
Message-Id: <199804281642.MAA19492@candle.pha.pa.us>
Subject: Re: [HACKERS] Revised proposal for libpq and FE/BE protocol changes
To: tgl@sss.pgh.pa.us (Tom Lane)
Date: Tue, 28 Apr 1998 12:42:51 -0400 (EDT)
Cc: pgsql-hackers@postgreSQL.org, pgsql-interfaces@postgreSQL.org
In-Reply-To: <7040.893780515@sss.pgh.pa.us> from "Tom Lane" at Apr 28,
	98 12:21:55 pm
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> 2. The RowDescription ('T') message is extended by adding a new value
> for each field.  Just after the type-size value, there will now be
> an int16 "atttypmod" value.  (Would someone provide text specifying
> exactly what this value means?)  libpq will store this value in
> a new "adtmod" field of PGresAttDesc structs.

From src/include/catalog/pg_attribute.h:

    /*
     * atttypmod records type-specific modifications supplied at table
     * creation time, and passes it to input and output functions as the
     * third argument.
     */

Currently only used for char() and varchar(), and includes a 4-byte
header.


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