Re: Online base backup from the hot-standby

2011/10/9 Jun Ishiduka <ishizuka(dot)jun(at)po(dot)ntts(dot)co(dot)jp>:

>  Insert WAL including a value of current FPW (on master)
>   * In the the same timing as update, they insert WAL (is named
>     XLOG_FPW_CHANGE). XLOG_FPW_CHANGE has a value of the changed FPW.
>   * When it creates CHECKPOINT, it adds a value of current FPW to the
>     CHECKPOINT WAL.

I can't see a reason why we would use a new WAL record for this,
rather than modify the XLOG_PARAMETER_CHANGE record type which was
created for a very similar reason.
The code would be much simpler if we just extend
XLOG_PARAMETER_CHANGE, so please can we do that?

The log message "full_page_writes on master is set invalid more than
once during online backup" should read "at least once" rather than
"more than once".

lastFpwDisabledLSN needs to be initialized.

Is there a reason to add lastFpwDisabledLSN onto the Control file? If
we log parameters after every checkpoint then we'll know the values
when we startup. If we keep logging parameters this way we'll end up
with a very awkward and large control file. I would personally prefer
to avoid that, but that thought could go either way. Let's see if
anyone else thinks that also.

Looks good.

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 Simon Riggs                   http://www.2ndQuadrant.com/
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