Greg Stark suggests here:
http://archives.postgresql.org/pgsql-hackers/2005-05/msg00966.php
that GiST could also be fixed to work with any subset of the index
columns, but it hasn't been done yet, unless Teodor and Oleg snuck
something in during that last round of GiST work.
GiST may work with a
Example:
assume a table of 10 columns, three of which are fname, lname, and dob.
If an index is created on (fname, lname, dob), will a query that
utilizes two of the columns ( select 'data' from table where fname = 'X'
and lname = 'Y') utilize the index?
thanks,
reid
--
On Mon, Sep 12, 2005 at 09:43:57AM -0400, Reid Thompson wrote:
> Example:
> assume a table of 10 columns, three of which are fname, lname, and dob.
> If an index is created on (fname, lname, dob), will a query that
> utilizes two of the columns ( select 'data' from table where fname = 'X'
> and lna
Alvaro Herrera wrote:
> On Mon, Sep 12, 2005 at 09:43:57AM -0400, Reid Thompson wrote:
>> Example:
>> assume a table of 10 columns, three of which are fname, lname, and
>> dob. If an index is created on (fname, lname, dob), will a query that
>> utilizes two of the columns ( select 'data' from table
On Mon, Sep 12, 2005 at 09:43:57AM -0400, Reid Thompson wrote:
> assume a table of 10 columns, three of which are fname, lname, and dob.
> If an index is created on (fname, lname, dob), will a query that
> utilizes two of the columns ( select 'data' from table where fname = 'X'
> and lname = 'Y') u
On Mon, Sep 12, 2005 at 10:05:36AM -0400, Reid Thompson wrote:
> Alvaro Herrera wrote:
> > Note that if your example query used the columns (lname, dob),
> > the answer would be "no."
>
> Why is that? In order to use an index, does the query have to utilize
> the 'first' element of the index?
In
On Mon, Sep 12, 2005 at 10:05:36AM -0400, Reid Thompson wrote:
> Alvaro Herrera wrote:
> > On Mon, Sep 12, 2005 at 09:43:57AM -0400, Reid Thompson wrote:
> >> Example:
> >> assume a table of 10 columns, three of which are fname, lname, and
> >> dob. If an index is created on (fname, lname, dob), wi
Alvaro Herrera <[EMAIL PROTECTED]> writes:
> On Mon, Sep 12, 2005 at 09:43:57AM -0400, Reid Thompson wrote:
>> Example:
>> assume a table of 10 columns, three of which are fname, lname, and dob.
>> If an index is created on (fname, lname, dob), will a query that
>> utilizes two of the columns ( sel
Alvaro Herrera <[EMAIL PROTECTED]> writes:
> On Mon, Sep 12, 2005 at 10:05:36AM -0400, Reid Thompson wrote:
>> Why is that? In order to use an index, does the query have to utilize
>> the 'first' element of the index?
> The "leftmost part." There's no way to scan an index if you don't know
> the
Tom Lane <[EMAIL PROTECTED]> writes:
> Alvaro Herrera <[EMAIL PROTECTED]> writes:
>
> > Yes, if it is selective enough. (It _can_ use the index, which does not
> > mean that it _will_ use it.) Note that if your example query used the
> > columns (lname, dob), the answer would be "no."
>
> Actua
Teodor Sigaev <[EMAIL PROTECTED]> writes:
> GiST may work with any subset of index columns too. Even in existing code I
> don't see any problem except NULL in a first column. GiST doesn't store
> tuples
> with leading NULL value (gist.c lines 174, 326), so index doesn't contained
> them.
Well,
Greg Stark <[EMAIL PROTECTED]> writes:
> Tom Lane <[EMAIL PROTECTED]> writes:
>> http://archives.postgresql.org/pgsql-committers/2005-06/msg00156.php
> Did that patch actually implement "skip scanning"?
No, it just removed the planner's arbitrary assumption that the index
methods wouldn't cope.
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