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Re: Two seperate problems with libpq - arrays and bytea edit

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Teunis Peters <teunis(at)wintersgift(dot)com>
Cc: pgsql-interfaces(at)postgresql(dot)org
Subject: Re: Two seperate problems with libpq - arrays and bytea edit
Date: 2005-05-14 18:51:13
Message-ID: 5157.1116096673@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-interfaces
Teunis Peters <teunis(at)wintersgift(dot)com> writes:
> I'm trying to figure out how to read from and write to bytea values and 
> array (specifically "text[2][]" for a key:value 'dictionary') and 
> cannot figure it out.

Well, since you are asking for binary output format from PQexecParams,
the bytea result is going to just be raw binary data: you should not be
trying to apply PQunescapeBytea to it.  I don't know the notation you
are using well enough to tell what's wrong with your second variant.

> Arrays I'm completely lost - I haven't a clue what the format would be.

Looking at array_send, the binary wire format is

	number of dimensions (int4)
	flags (int4)
	element type id (Oid)
	for each dimension:
		dimension length (int4)
		dimension lower subscript bound (int4)
	for each array element:
		element value, in the appropriate format

The "flags" are currently always 0, and I would recommend punting if
you see something else, since something else would very possibly
indicate a change in the wire format.

Don't forget that the wire format for integers is network byte order
(ie, big-endian).

			regards, tom lane

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