On Tue, Oct 4, 2016 at 8:05 AM, Chenxi Li wrote:
> How is cardinality estimation for "group by" is done and where is the code
> doing that?
I would suggest that you start by looking at estimate_num_groups() in
src/backend/utils/adt/selfuncs.c. You might also want to look at
cost_agg() in src/bac
Friends,
How is cardinality estimation for "group by" is done and where is the code
doing that?
Best Regards,
Chenxi Li
Gregory Stark wrote:
> Peter Eisentraut writes:
>
> > The standard represents multidimensional arrays as arrays of arrays (like
> > in
> > C).
>
> Uh, C doesn't represent multidimensional arrays as arrays of arrays so you've
> lost me already.
I think he meant to say C _can_ represent multidi
Peter Eisentraut writes:
> The standard represents multidimensional arrays as arrays of arrays (like in
> C).
Uh, C doesn't represent multidimensional arrays as arrays of arrays so you've
lost me already.
--
Gregory Stark
EnterpriseDB http://www.enterprisedb.com
Ask me about En
On Sunday 01 March 2009 19:40:16 Tom Lane wrote:
> I wrote:
> > The standard doesn't have multi-dimensional arrays, so it's entirely
> > possible that somewhere in it there is wording that makes cardinality()
> > equivalent to the length of the first dimension. But I concur with
> > Andrew that th
On Sun, 1 Mar 2009, Tom Lane wrote:
> I wrote:
> > The standard doesn't have multi-dimensional arrays, so it's entirely
> > possible that somewhere in it there is wording that makes cardinality()
> > equivalent to the length of the first dimension. But I concur with
> > Andrew that this is flat w
2009/3/1 Tom Lane :
> I wrote:
>> The standard doesn't have multi-dimensional arrays, so it's entirely
>> possible that somewhere in it there is wording that makes cardinality()
>> equivalent to the length of the first dimension. But I concur with
>> Andrew that this is flat wrong when extended to
I wrote:
> The standard doesn't have multi-dimensional arrays, so it's entirely
> possible that somewhere in it there is wording that makes cardinality()
> equivalent to the length of the first dimension. But I concur with
> Andrew that this is flat wrong when extended to m-d arrays.
I poked arou
Andrew Dunstan writes:
> Grzegorz Jaskiewicz wrote:
>> On 1 Mar 2009, at 00:52, Andrew Dunstan wrote:
>>> We seem to have acquired a cardinality() function with almost no
>>> discussion, and it has semantics that are a bit surprising to me. I
>>> should have thought cardinality(array) would be t
Grzegorz Jaskiewicz wrote:
On 1 Mar 2009, at 00:52, Andrew Dunstan wrote:
We seem to have acquired a cardinality() function with almost no
discussion, and it has semantics that are a bit surprising to me. I
should have thought cardinality(array) would be the total number of
elements in t
On 1 Mar 2009, at 00:52, Andrew Dunstan wrote:
We seem to have acquired a cardinality() function with almost no
discussion, and it has semantics that are a bit surprising to me. I
should have thought cardinality(array) would be the total number of
elements in the array. Instead, it seems
We seem to have acquired a cardinality() function with almost no
discussion, and it has semantics that are a bit surprising to me. I
should have thought cardinality(array) would be the total number of
elements in the array. Instead, it seems it is a synonym for
array_length(array,1). Is that
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