Re: Patch for PGunescapeBytea

(I will apply the newer version.)

Your patch has been added to the PostgreSQL unapplied patches list at:

    http://momjian.postgresql.org/cgi-bin/pgpatches

I will try to apply it within the next 48 hours.

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Ben Lamb wrote:
> Hi,
>
> I found the libpq function PGunescapeBytea a little slow. It was taking a
> minute and a half to decode a 500Kb on a fairly fast machine. I think the
> culprit is sscanf.
>
> I attach a patch that replaces the function with one used to perform the same
> task in pyPgSQL (a Python interface to PostgreSQL). This code was written by
> Billy Allie, author of pyPgSQL. I've changed a few variable names to match
> those in the original code and removed a bit of Pythonness.
>
> Billy has kindly looked at the code and points out that it is slightly
> stricter than the original implementation and if it encounters an invalid
> bytea such as '\12C' it drops the unescape '\' and outputs '12C'.
>
> The code is licensed by the author under a BSD license.
>
> I've performed limited testing of the function by putting JPEGs into
> PostgreSQL, extracting them using them using the new function and diffing
> against the original files.
>
> The new function is significantly faster on my machine with the JPEGs being
> decoded in less than a second. I attach a modified libpq example program that
> I used for my testing.
>
> Regards,
>
> Ben Lamb.
>
> The patch modifies fe-exec.c in /src/interfaces/libpq from PostgreSQL 7.3.2.

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