Re: Performance Improvement by reducing WAL for Update Operation

On 28 December 2012 10:21, Simon Riggs <simon@2ndquadrant.com> wrote:

> * There is a fixed 75% heuristic in the patch.

I'm concerned that we're doing extra work while holding the buffer
locked, which will exacerbate any block contention that exists.

We have a list of the columns that the UPDATE is touching since we use
that to check column permissions for the UPDATE. Which means we should
be able to use that list to check only the columns actually changing
in this UPDATE statement.

That will likely save us some time during the compression check.

Can you look into that please? I don't think it will be much work.

I've moved this to the next CF. I'm planning to review this one first.

-- Simon Riggs                   http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training & Services