On Tue, Nov 18, 2008 at 3:54 PM, Thomas Kellerer <spam_eater@xxxxxxx> wrote: > Hmm. I was not talking about an index _fast full_ scan, I was talking about > index scans in general. Personally I have never seen Oracle using a table > scan (whatever kind) if all columns in the select are present in the index. > > And the manual actually suggests the same: > > "If the statement accesses only columns of the index, then Oracle reads the > indexed column values directly from the index, rather than from the table" > http://download.oracle.com/docs/cd/B19306_01/server.102/b14211/optimops.htm#i52300 The manual is wrong. >> Those are essentially clustered indexes, and they're not quite stored >> exactly the same.. >> > Hmm, my understanding of a clustered index, that it "orders" the table data > according to the index, but there is still "table data" and "index data", > right? > > That is a bit different to an index-organized table were only a B-Tree index > exists. This is not mandatory, but for my example (a link table with two PK > columns) only a B-Tree index is created. Well, clustered indexes mean different things to different vendors. Oracle's implementation stores the data with the index as does SQL Server, but in a little different fashion. -- Jonah H. Harris, Senior DBA myYearbook.com -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
