|From:||Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru>|
|Subject:||Re: [PATCH]make pg_rewind to not copy useless WAL files|
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On Fri, Sep 29, 2017 at 8:10 PM, chenhj <chjischj(at)163(dot)com> wrote:
> On 2017-09-30 00:53:31，"chenhj" <chjischj(at)163(dot)com> wrote:
> On 2017-09-29 19:29:40，"Alexander Korotkov" <a(dot)korotkov(at)postgrespro(dot)ru>
> On Fri, Sep 29, 2017 at 10:07 AM, chenhj <chjischj(at)163(dot)com> wrote:
> OK. That makes sense. Thank you for the explanation.
> I still have some minor comments.
>> + * Save the WAL filenames of the divergence and the current WAL insert
>> + * location of the source server. Later only the WAL files between
>> + * would be copied to the target data directory.
> Comment is outdated. We don't save filenames anymore, now we save segment
>> + * Note:The later generated WAL files in the source server before the
>> + * of the copy of the data files must be made available when the
>> + * server is started. This can be done by configuring the target
>> server as
>> + * a standby of the source server.
>> + */
> You miss space after "Note:". Also, it seems reasonable for me to leave
> empty line before "Note:".
> # Setup parameter for WAL reclaim
> Parameter*s*, because you're setting up multiple of them.
> # The accuracy of imodification from pg_ls_waldir() is seconds, so sleep
>> one seconds
> One second without "s".
> Also, please check empty lines in 006_wal_copy.pl to be just empty lines
> without tabs.
> Thanks for your comments, i had fix above problems.
> And also add several line breaks at long line in 006_wal_copy.pl
> Please check this patch again.
> Sorry, patch v6 did not remove tabs in two empty lines, please use the new
Great. Now code of this patch looks good for me.
However, we forgot about documentation.
> 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.
At least, this paragraph need to be adjusted, because it states whose files
are copied. And probably latter paragraphs whose state about WAL files.
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