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

On Sat, Sep 30, 2017 at 8:18 PM, chenhj <chjischj@163.com> wrote:

On 2017-09-30 02:17:54，"Alexander Korotkov" <a.korotkov@postgrespro.ru> wrote:

Great.  Now code of this patch looks good for me.

However, we forgot about documentation.

  <para>
   The result is equivalent to replacing the target data directory with the
   source one. Only changed blocks from relation files are copied;
   all other files are copied in full, including configuration files. The
   advantage of <application>pg_rewind</> over taking a new base backup, or
   tools like <application>rsync</>, is that <application>pg_rewind</> does
   not require reading through unchanged blocks in the cluster. This makes
   it a lot faster when the database is large and only a small
   fraction of blocks differ between the clusters.
  </para>

At least, this paragraph need to be adjusted, because it states whose files are copied.  And probably latter paragraphs whose state about WAL files.

Your are rigth.

I wrote a draft as following, but i'm afraid whether the english statement is accurate.

I'm not native english speaker too :(

Only the WAL files between the point of divergence and the current WAL insert location of the source server are copied, *for* other WAL files are useless for the target server. 

I'm not sure about this usage of word *for*.  For me, it probably should be just removed.  Rest of changes looks good for me.  Please, integrate them into the patch.