On Tue, Nov 18, 2008 at 3:54 PM, Thomas Kellerer <[EMAIL PROTECTED]> 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 th
Jonah H. Harris wrote on 18.11.2008 20:58:
On Tue, Nov 18, 2008 at 2:33 PM, Thomas Kellerer <[EMAIL PROTECTED]> wrote:
If all the columns from the select list are available in the index, then
Oracle will always prefer the index scan over a table scan (at least I have
never seen something else).
Scott Marlowe wrote:
>> They aren't borrowing anything, Oracle has had this functionality
>> since at least Oracle 8i (1999).
>
> Whoa, calm down Francis. I'm not suggesting they stole it or
> something. Just that they're using the same basic concepts.
Oh, and citation needed. I don't
On Tue, Nov 18, 2008 at 3:45 PM, Joshua D. Drake <[EMAIL PROTECTED]> wrote:
> Off topic much?
Hey, all I did was make a joke; other people wanted to get all
*correct* about it :)
Anyway, as this has been discussed at least twenty times before, this
is a waste of a thread.
--
Jonah H. Harris, Se
On Tue, 2008-11-18 at 15:28 -0500, Jonah H. Harris wrote:
> On Tue, Nov 18, 2008 at 3:09 PM, Scott Marlowe <[EMAIL PROTECTED]> wrote:
> > Oh, and citation needed. I don't remember seeing anything about
> > oracle using indexes as sole storage units back in 8i
>
> Your memory-foo is weak. See ORG
On Tue, Nov 18, 2008 at 3:09 PM, Scott Marlowe <[EMAIL PROTECTED]> wrote:
> Oh, and citation needed. I don't remember seeing anything about
> oracle using indexes as sole storage units back in 8i
Your memory-foo is weak. See ORGANIZATION INDEX:
http://download-west.oracle.com/docs/cd/A87860_01/
On Tue, Nov 18, 2008 at 3:07 PM, Scott Marlowe <[EMAIL PROTECTED]> wrote:
>> They aren't borrowing anything, Oracle has had this functionality
>> since at least Oracle 8i (1999).
>
> Whoa, calm down Francis.
My name's not Francis :)
> I'm not suggesting they stole it or something. Just that they
On Tue, Nov 18, 2008 at 1:07 PM, Scott Marlowe <[EMAIL PROTECTED]> wrote:
> On Tue, Nov 18, 2008 at 1:03 PM, Jonah H. Harris <[EMAIL PROTECTED]> wrote:
>> On Tue, Nov 18, 2008 at 2:57 PM, Scott Marlowe <[EMAIL PROTECTED]> wrote:
>>> Sounds like they're borrowing the code from innodb that does much
On Tue, Nov 18, 2008 at 2:57 PM, Scott Marlowe <[EMAIL PROTECTED]> wrote:
> Sounds like they're borrowing the code from innodb that does much the
> same thing. In Innodb, if a field is indexed, it lives only as an
> index, not in the table and an index at the same time.
They aren't borrowing anyt
On Tue, Nov 18, 2008 at 1:03 PM, Jonah H. Harris <[EMAIL PROTECTED]> wrote:
> On Tue, Nov 18, 2008 at 2:57 PM, Scott Marlowe <[EMAIL PROTECTED]> wrote:
>> Sounds like they're borrowing the code from innodb that does much the
>> same thing. In Innodb, if a field is indexed, it lives only as an
>> i
On Tue, Nov 18, 2008 at 2:33 PM, Thomas Kellerer <[EMAIL PROTECTED]> wrote:
> If all the columns from the select list are available in the index, then
> Oracle will always prefer the index scan over a table scan (at least I have
> never seen something else). Even for a SELECT that returns all rows
On Tue, Nov 18, 2008 at 12:33 PM, Thomas Kellerer <[EMAIL PROTECTED]> wrote:
> If all the columns from the select list are available in the index, then
> Oracle will always prefer the index scan over a table scan (at least I have
> never seen something else). Even for a SELECT that returns all rows
Jonah H. Harris wrote on 18.11.2008 20:15:
On Tue, Nov 18, 2008 at 2:02 PM, Scara Maccai <[EMAIL PROTECTED]> wrote:
SELECT A FROM myTAB where A <1
only uses the index (if there's an index defined for A) in Oracle.
Well, not exactly. That's called a "covered" index because the query
could
On Tue, Nov 18, 2008 at 2:02 PM, Scara Maccai <[EMAIL PROTECTED]> wrote:
> SELECT A FROM myTAB where A <1
>
> only uses the index (if there's an index defined for A) in Oracle.
Well, not exactly. That's called a "covered" index because the query
could be satisfied directly from the index (the
On Tue, Nov 18, 2008 at 12:48 PM, Sam Mason <[EMAIL PROTECTED]> wrote:
>> It makes sense to me,
>> but I don't understand is how other databases (such as Oracle) do it.
>
> There are tradeoffs in both directions; [...] but Oracle's way is more
> optimized
For the most part, that's all you needed
> FWIW, I believe that count(*) is pretty slow in Oracle too.
Well COUNT was only an example. I think (but I'm not sure AT ALL) that
SELECT A FROM myTAB where A <1
only uses the index (if there's an index defined for A) in Oracle.
But mine was just curiosity... which I think you and Sam an
Sam Mason <[EMAIL PROTECTED]> writes:
> On Tue, Nov 18, 2008 at 04:49:35PM +, Scara Maccai wrote:
>> It makes sense to me,
>> but I don't understand is how other databases (such as Oracle) do it.
> I believe Oracle maintains a separate log (not sure how it's structured)
> that contains this in
On Tue, Nov 18, 2008 at 04:49:35PM +, Scara Maccai wrote:
> if I got it right the reason some aggregates (such as COUNT) using
> only index columns are "slow" on postgresql is that it uses MVCC, so
> it has to read the data as well as the index.
Every aggregate (of which COUNT is just one exam
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