On Thu, Oct 20, 2016 at 8:44 PM, Petr Jelinek <p...@2ndquadrant.com> wrote:

> WARM can do WARM update 50% of time, indirect index can do HOT update
> 100% of time (provided the column is not changed), I don't see why we
> could not have both solutions.
I think the reason why I restricted WARM to one update per chain, also
applies to indirect index. For example, if a indirect column value is
changed from 'a' to 'b' and back to 'a', there will be two pointers from
'a' to the PK and AFAICS that would lead to the same duplicate scan issue.

We have a design to convert WARM chains back to HOT and that will increase
the percentage of WARM updates much beyond 50%. I was waiting for feedback
on the basic patch before putting in more efforts, but it went unnoticed
last CF.

> That all being said, it would be interesting to hear Álvaro's thoughts
> about which use-cases he expects indirect indexes to work better than WARM.
Yes, will be interesting to see that comparison. May be we need both or may
be just one. Even better may be they complement each other.. I'll also put
in some thoughts in this area.


 Pavan Deolasee                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services

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