Re: GiST for range types (was Re: Range Types - typo + NULL string constructor)

On 01.11.2011 06:33, Jeff Davis wrote:
> On Mon, 2011-10-24 at 15:05 +0400, Alexander Korotkov wrote:
>
>> I think implementing subtype_diff for each datatype is ok. We could
>> implement some universal function based on minus operator and casting
>> to double precision. But such solution might be unacceptable in
>> both predictability (operator and casting function might do not the
>> things we expect) and performance.
>>
> Done.
>
> Everything is complete in this patch with the exception of two optional
> things, which I still intend to do but might best be done in a separate
> commit:
>
> * support typmod for ranges
> * support casts between different range types
>
> Both of these things, I believe, require the introduction of an
> RangeCoerceExpr, similar to ArrayCoerceExpr. That's fine, but it creates
> a rather large diff, so it might be best left for a later commit.

Using the test table from the rangetypes test case:

postgres=# select * from test_range_gist where 10 <@ ir;
ERROR: unsupported type: 3904

This seems to be coming from the selectivity estimation function. The
selectivity function for <@ is scalargtsel, which is usually used for
scalar > and >=. That doesn't seem right. But what do we store in the
statistics for range types in the first place, and what would be the
right thing to do for selectivity estimation?

I'll dig deeper into this tomorrow...

--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com