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References: <478226FB.6030306@fmed.uba.ar>
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From: Erik Jones <erik@myemma.com>
Subject: Re: reading WAL files in python
Date: Mon, 7 Jan 2008 12:53:59 -0600
To: Gerardo Herzig <gherzig@fmed.uba.ar>


On Jan 7, 2008, at 7:19 AM, Gerardo Herzig wrote:

> Hi all. Im having some fun trying to write my own replication =20
> system using python. I will use the postgres own WAL archiving to =20
> write the files,  then my app will read them and do some stuff. As =20
> im not a C programmer, im stuck in the mission of reading the =20
> binary files.
>
> I guess im needing to know the internals of how wals archives are, =20
> how big the buffer has to be, in order to have a complete sql command.
>
> Can someone point some advice?
> I was trying to understad src/backend/access/transam/xlog.c, but =20
> seems too difficult to me :(

The biggest problem with what you're wanting to do here is that the =20
data written to the WALL archives isn't going to be at all easily =20
translatable into SQL statements.  AFAIK, the WAL data records on-=20
disk file changes, i.e. it's strictly a binary mode scenario.  As =20
someone has already suggested, if you want to learn more about =20
Postgres and Python, look at Skytools.  I'm not just saying to use =20
it, read the code and, if you like, offer help with patches.

Erik Jones

DBA | Emma=AE
erik@myemma.com
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