Re: Why is indexonlyscan so darned slow?

On Thu, May 17, 2012 at 11:35 AM, Joshua Berkus <josh@agliodbs.com> wrote:
> Jeff,
>
> That's in-RAM speed ... I ran the query twice to make sure the index was cached, and it didn't get any better.  And I
meant5X per byte rather than 5X per tuple. 

Ah, OK that makes more sense.  I played around with this, specifically
count(*), quite a bit when IOS first came out, and I attributed a
large part of the time to the code that forms a tuple out of raw
bytes, and the code that advances the aggregate.  The first one is
probably more a per-tuple cost than per byte, and the second
definitely is per tuple cost.

I can't find my detailed notes from this work, so this is just from memory.

Cheers,

Jeff