Gregory Stark <[EMAIL PROTECTED]> writes:
> This is something that needs some serious thought though. In the case of
> partitioned tables I've seen someone get badly messed up plans because they
> had a couple hundred partitions each of which estimated to return 1 row. In
> fact of course they all
"Tom Lane" <[EMAIL PROTECTED]> writes:
> Right. As a matter of policy we never estimate less than one matching
> row; and I've seriously considered pushing that up to at least two rows
> except when we see that the query condition matches a unique constraint.
> You can get really bad join plans
Jeff Davis <[EMAIL PROTECTED]> writes:
> On Wed, 2008-04-30 at 10:43 -0400, Tom Lane wrote:
>> Surely that's not very sane? The MCV list plus histogram generally
>> don't include every value in the table.
> My understanding of Len's question is that, although the MCV list plus
> the histogram don
On Wed, 2008-04-30 at 10:43 -0400, Tom Lane wrote:
> > Instead I would expect an estimate of "rows=0" for values of const
> > that are not in the MCV list and not in the histogram.
>
> Surely that's not very sane? The MCV list plus histogram generally
> don't include every value in the table. II
"Len Shapiro" <[EMAIL PROTECTED]> writes:
> I asked about n_distinct, whose documentation reads in part "The
> negated form is used when ANALYZE believes that the number of distinct
> values is likely to increase as the table grows". and I asked about
> why ANALYZE believes that the number of dist
Tom,
Thank you for your prompt reply.
On Tue, Apr 29, 2008 at 10:19 PM, Tom Lane <[EMAIL PROTECTED]> wrote:
> Len Shapiro <[EMAIL PROTECTED]> writes:
> > 1. Why does Postgres come up with a negative n_distinct?
>
> It's a fractional representation. Per the docs:
>
> > stadistinct float4
Len Shapiro <[EMAIL PROTECTED]> writes:
> 1. Why does Postgres come up with a negative n_distinct?
It's a fractional representation. Per the docs:
> stadistinct float4 The number of distinct nonnull data values in
> the column. A value greater than zero is the actual number of distin
I hope I am posting to the right list.
I am running Postgresql 8.1.9 and don't understand the behavior of
histograms for data items not in the MVC list. I teach databases and
want to use Postgres as an example. I will appreciate any help that
anyone can provide.
Here is the data I am using. I a
