Re: Suggestion for optimization

Christopher Kings-Lynne wrote:
> > > Af far as I know Oracle doesn't have any short cut (along the lines of
> > > what is being discussed in this thread) for this operation. However
> > > Oracle is more efficient in providing the answer than postgres
> > currently
> > > is. While postgres needs to perform a full scan on the table, Oracle
> > > will only need to perform a full index scan on the primary key if one
> > > exists. Since the index will likely have much less data than the full
> >
> > Under Postgres, a full index scan is generally more expensive than a full
> > table scan since indices, particularly btree, carry a large amount of meta
> > data and theefore consume more pages.
>
> Don't forget that Postgres also doesn't store tids in the index, so must

I assume you mean xid here. tids are in the index or there would be no
way to find the heap row. :-)

> always check with the main table that a row is visible in current
> transaction.

--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 853-3000
+ If your life is a hard drive, | 830 Blythe Avenue
+ Christ can be your backup. | Drexel Hill, Pennsylvania 19026