Обсуждение: Another little xlog change idea

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Another little xlog change idea

От
Tom Lane
Дата:
As long as I'm about to change the xlog page headers, I have another
little idea.  Wouldn't it be a good idea to allow three backup pages
per xlog record, not only two?  It seems like three pages would be
a natural requirement for logging operations like index page splits.

We could support as many as four pages per record, but that would mean
having no free global bits in the info byte, which might be a bad idea.
I think three page bits and one free bit is a good compromise.
Thoughts?
        regards, tom lane


RE: Another little xlog change idea

От
"Mikheev, Vadim"
Дата:
> As long as I'm about to change the xlog page headers, I have another
> little idea.  Wouldn't it be a good idea to allow three backup pages
> per xlog record, not only two?  It seems like three pages would be
> a natural requirement for logging operations like index page splits.

On index splits we don't backup left and right whole pages - just part
of pages filled by index tuples. This saves us ~ 8K for indices with
small keys.

> We could support as many as four pages per record, but that would mean
> having no free global bits in the info byte, which might be a 
> bad idea. I think three page bits and one free bit is a good compromise.
> Thoughts?

You almost forget that we are in beta and should fix bugs, not implement
features which useless in current version -:) Add comments and that will
be enough, no?

Vadim