On Wed, Feb 08, 2006 at 06:02:08PM +0100, Dick Kniep wrote:
> On Wednesday 08 February 2006 06:18, Tom Lane wrote:
> > Dick Kniep <[EMAIL PROTECTED]> writes:
> > > Does this also affect if you have many NULL values in the key? So testing
> > > Not is NULL would also be affected?
> >
> > IS NOT NULL
Dick Kniep <[EMAIL PROTECTED]> writes:
> Does this mean that if you have a table that has many rows, and 95% of the
> rows contain a NULL value for a field, that indexing will be useless, because
> it will always do a tablescan?
Any time you have 95% of the rows of the table with the same valu
On Wednesday 08 February 2006 06:18, Tom Lane wrote:
> Dick Kniep <[EMAIL PROTECTED]> writes:
> > Does this also affect if you have many NULL values in the key? So testing
> > Not is NULL would also be affected?
>
> IS NOT NULL isn't an indexable operation, so your question doesn't really
> apply :
Dick Kniep <[EMAIL PROTECTED]> writes:
> Does this also affect if you have many NULL values in the key? So testing Not
> is NULL would also be affected?
IS NOT NULL isn't an indexable operation, so your question doesn't really
apply :-(
regards, tom lane
-
Hi list,
Does this also affect if you have many NULL values in the key? So testing Not
is NULL would also be affected?
Cheers,
Dick Kniep
On Tuesday 07 February 2006 23:13, Tom Lane wrote:
> [EMAIL PROTECTED] writes:
> > Quoting Tom Lane <[EMAIL PROTECTED]>:
> >> In 8.0, the descent code can do
[EMAIL PROTECTED] writes:
> Quoting Tom Lane <[EMAIL PROTECTED]>:
>> In 8.0, the descent code can do
>> either "first entry >= X" or "first entry > X", and the positioning
>> rules never need to step more than one entry to locate the desired
>> starting position (details left as exercise for the re
Quoting Tom Lane <[EMAIL PROTECTED]>:
[EMAIL PROTECTED] writes:
In the 8.0 release notes, (section E.10.4.1), I noticed this
statement:
Improve B-tree index performance for duplicate keys (Dmitry Tkach, Tom)
This improves the way indexes are scanned when many duplicate
values
[EMAIL PROTECTED] writes:
> In the 8.0 release notes, (section E.10.4.1), I noticed this
> statement:
> Improve B-tree index performance for duplicate keys (Dmitry Tkach, Tom)
> This improves the way indexes are scanned when many duplicate
> values exist in the index.
> Can someone d
I'm currently running postgresql 7.4.8. Our two biggest tables have
indexes on (x, y), where x, y are integers, and there are often
many y values per x value. The ratio can be anywhere from 1:1 to 20:1.
In the 8.0 release notes, (section E.10.4.1), I noticed this
statement:
Improve B-tree
