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.
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