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Re: type recv/send functions

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Greg Stark <gsstark(at)mit(dot)edu>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: type recv/send functions
Date: 2006-05-30 03:42:36
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
Greg Stark <gsstark(at)mit(dot)edu> writes:
> "both return something" seems like an odd axis to measure.

> In one case it's given pointer to the entire message, picks out the piece it's
> interested in and advances the cursor.

This is just a trivial optimization compared to being handed a bytea
input, which would be the "clean" version.  (I had originally thought
we could fake a bytea input without any copying, much as is done in the
text input path, but that fails on machines that are persnickety about
alignment: the "bytea" length word might not be word-aligned depending
on message contents.)

> What I'm pondering here is that the extra copy to construct the bytea for
> every single data type being output seems like it would be a pretty big
> contribution to the complaint that postgres takes too much cpu in cases that
> should be entirely i/o bound.

Since approximately zero percent of the people making that complaint are
using binary output, I don't think it matters.

			regards, tom lane

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