From: | Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp> |
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To: | Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp |
Cc: | pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: RangeType internal use |
Date: | 2015-02-06 07:34:45 |
Message-ID: | 20150206.163445.146207935.horiguchi.kyotaro@lab.ntt.co.jp |
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Thread: | |
Lists: | pgsql-hackers |
Hi, from nearby:)
> I wonder why I cannot find a way to get a range type for a given (sub-)
> type. I would like to build a RangeType from Datum's of lower and upper
> bounds. Much like how construct_array() builds an ArrayType from a Datum
> array of elements given elements' type info.
>
> Is there some way I do not seem to know? If not, would it be worthwhile
> to make something like construct_range() that returns a RangeType given
> Datum's of lower and upper bounds and subtype info?
make_range needs the range type itself.
On SQL interfalce, you can get range type coresponds to a base
type by looking up the pg_range catalog.
SELECT rngtypid::regtype, rngsubtype::regtype
FROM pg_range WHERE rngsubtype = 'int'::regtype;
rngtypid | rngsubtype
-----------+------------
int4range | integer
But there's only one syscache for this catalog which takes range
type id. So the reverse resolution rngsubtype->rngtype seems not
available. TypeCahce has only comparison function info as surely
available element related to range types but this wouldn't
help. I think scanning the entire cache is not allowable even if
possible.
Perhaps what is needed is adding RANGESUBTYPE syscache but I
don't know whether it is allowable or not.
Thoughts?
regards,
--
Kyotaro Horiguchi
NTT Open Source Software Center
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