Re: [HACKERS] [PATCH]make pg_rewind to not copy useless WAL files

On Sun, Sep 17, 2017 at 3:19 AM, Alexander Korotkov
<a.korotkov@postgrespro.ru> wrote:
> Hi!
>
> On Sat, Sep 16, 2017 at 5:56 PM, chenhj <chjischj@163.com> wrote:
>>
>> This patch optimizes the above mentioned issues, as follows:
>> 1. In the target data directory, do not delete the WAL files before the
>> divergence.
>> 2. When copying files from the source server, do not copy the WAL files
>> before the divergence and the WAL files after the current WAL insert
>> localtion.
>
>
> Looks like cool optimization for me.  Please, add this patch to the next
> commitfest.

Agreed.

> Do you think this patch should modify pg_rewind tap tests too?  It would be
> nice to make WAL files fetching more covered by tap tests.  In particular,
> new tests may generate more WAL files and make sure that pg_rewind fetches
> only required files among them.

This looks mandatory to me. Using pg_switch_wal() and a minimum amount
of WAL generated you could just make the set of WAL segments skipped
minimal data.

I have not checked in details, but I think that the positions where
you are applying the filters are using the right approach.

!         !(strncmp(path, "pg_wal", 6) == 0 && IsXLogFileName(path + 7) &&
Please use XLOGDIR here.
-- 
Michael


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