Re: [WIP] Performance Improvement by reducing WAL for Update Operation

On 3 August 2012 12:46, Amit kapila <amit(dot)kapila(at)huawei(dot)com> wrote:

> Frame the new tuple from old tuple and WAL record:

Sounds good.

I'd suggest we do this only when the saving is large enough for
benefit, rather than do this every time.

You don't mention whether or not the old and the new tuple are on the
same data block.

Personally, I think it will be important to ensure the above,
otherwise recovery will require much additional code for that case.
And that code will be prone to race conditions and performance issues.

Please also bear in mind that Andres will be looking to include the PK
columns in every WAL record for BDR. That could be an option, but I
doubt there is much value in excluding PK columns. I think I'd want
them to be there for debugging purposes so we can prove this code is
correct in production, since otherwise this could be a source of data
loss bugs.

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