Re: using pg_basebackup for point in time recovery

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От David G. Johnston
Тема Re: using pg_basebackup for point in time recovery
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Msg-id CAKFQuwZ0i7ZXFvWz6dqyz2-t=CSPhj0eKFWRKQNWnRfF4hfufA@mail.gmail.com
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Ответ на Re: using pg_basebackup for point in time recovery  (Vik Fearing <vik.fearing@2ndquadrant.com>)
Ответы Re: using pg_basebackup for point in time recovery
Re: using pg_basebackup for point in time recovery
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On Thu, Jun 21, 2018 at 4:26 PM, Vik Fearing <vik.fearing@2ndquadrant.com> wrote:
On 21/06/18 07:27, Michael Paquier wrote:
> Attached is a patch which includes your suggestion.  What do you think?
> As that's an improvement, only HEAD would get that clarification.

Say what?  If the clarification applies to previous versions, as it
does, it should be backpatched.  This isn't a change in behavior, it's a
change in the description of existing behavior.

Generally only actual bug fixes get back-patched; but I'd have to say this looks like it could easily be classified as one.

Before: These are backups that cannot be used for PITR
After: These are backups that could be used for PITR if ...

Changing a cannot to a can seems like we are fixing a bug in the documentation.

Some comments on the patch itself:

"recover up to the wanted recovery point." - "desired recovery point" reads better to me

====
"These backups are typically much faster to backup and restore" - "These backups are typically much faster to create and restore"; avoid repeated use of the word backup

"but can result as well in larger backup sizes" - "but can result in larger backup sizes", drop the unnecessary 'as well'

"sizes, so the speed of one method or the other is to evaluate carefully first" - that is just wrong as-is; suggest just removing it.
====

To cover the last three items as a whole I'd suggest:

"These backups are typically much faster to create and restore, but generate larger file sizes, compared to pg_dump."

For the last sentence I'd suggest:

"Note that because WAL cannot be applied on top of a restored pg_dump backup it is considered a cold backup and cannot be used for point-in-time-recovery."

I like adding "cold backup" here to help contrast and explain why a base backup is considered a "hot backup".  The rest is style to make that flow better.

David J.

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