| From: | Mark Kirkwood <markir(at)paradise(dot)net(dot)nz> |
|---|---|
| To: | Simon Riggs <simon(at)2ndquadrant(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>, Pål Stenslet <paal(dot)stenslet(at)exie(dot)com>, pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: Should Oracle outperform PostgreSQL on a complex |
| Date: | 2005-12-18 22:04:37 |
| Message-ID: | 43A5DCF5.8010604@paradise.net.nz |
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| Lists: | pgsql-performance |
Simon Riggs wrote:
> On Sun, 2005-12-18 at 17:07 +1300, Mark Kirkwood wrote:
>
>>Tom Lane wrote:
>>
>>
>>>>2. transform joins into subselects, then return subselect rows via an
>>>>index bitmap. Joins are performed via a bitmap addition process.
>>
>>Looks like 8.1 pretty much does this right now:
>
>
> Good analysis.
>
> 8.1 doesn't do:
> - the transforms sufficiently well (you just performed them manually)
Absolutely - I was intending to note that very point, but it got lost
somewhere between brain and fingers :-)
> - doesn't AND together multiple bitmaps to assist with N-way joins
>
Ah yes - I had overlooked that, good point!
Cheers
Mark
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