From: | Heikki Linnakangas <hlinnakangas(at)vmware(dot)com> |
---|---|
To: | Christoph Berg <cb(at)df7cb(dot)de>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: includedir_internal headers are not self-contained |
Date: | 2014-04-28 12:55:45 |
Message-ID: | 535E4FD1.6000100@vmware.com |
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Lists: | pgsql-hackers |
On 04/28/2014 03:29 PM, Christoph Berg wrote:
> Re: Heikki Linnakangas 2014-04-28 <535E09B7(dot)3090706(at)vmware(dot)com>
>>> Comments? If there's anyone who has a really good use-case for using
>>> relpath() from outside the backend, better speak up.
>>
>> I'm using it in the pg_rewind tool. It needs to know how to map relfilenodes
>> to physical files.
>>
>> It has quite intimate knowledge of the on-disk layout anyway, so it wouldn't
>> be the end of the world to just copy-paste that code. But would rather not,
>> of course.
>
> Isn't pg_rewind so low-level server-close that it needs tons of server
> headers anyway, including one that would still have relpath()? We are
> talking here about what headers pure client apps need.
It knows how to decode WAL, similar to pg_xlogdump. And it knows about
the data directory layout, in particular, how relfilenodes are mapped to
physical files. Those are the low-level parts. So, it certainly needs
some server headers, but I wouldn't call it tons.
- Heikki
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