Re: MVCC overheads

On 7 July 2016 at 17:45, Pete Stevenson <etep(dot)nosnevets(at)gmail(dot)com> wrote:

> Hi postgresql hackers -
>
> I would like to find some analysis (published work, blog posts) on the
> overheads affiliated with the guarantees provided by MVCC isolation. More
> specifically, assuming the current workload is CPU bound (as opposed to IO)
> what is the CPU overhead of generating the WAL, the overhead of version
> checking and version creation, and of garbage collecting old and
> unnecessary versions? For what it’s worth, I am working on a research
> project where it is envisioned that some of this work can be offloaded.
>

MVCC is a benefit, not an overhead. To understand that you should compare
MVCC with a system that performs S2PL.

If you're thinking that somehow consistency isn't important, I'd hope that
you also consider some way to evaluate the costs associated with
inconsistent and incorrect results in applications, or other architectural
restrictions imposed to make that possible. It's easy to make assumptions
in the lab that don't work in the real world.

--
Simon Riggs http://www.2ndQuadrant.com/
<http://www.2ndquadrant.com/>
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