Re: Is there a reason why Postgres doesn't have Byte or tinyint?

On Sun, Jan 8, 2012 at 06:54, Mike Christensen <mike(at)kitchenpc(dot)com> wrote:
>>>>>> According to the manuals, Postgres has smallint (2 byte), integer (4
>>>>>> bytes) and bigint (8 bytes)..  I use a lot of structures with "bytes"
>>>>>> in my code and it's kinda annoying to cast DB output from Int16 to
>>>>>> Byte every time, especially since there's no explicit cast in .NET and
>>>>>> you have to use System.Convert().
>>>>>>
>>>>>> Is there a work-around, or do people just cast or use Int16 in their
>>>>>> data structures?  Just wondering..  I know on modern computers it
>>>>>> probably doesn't make any difference anyway..
>>>>>
>>>>>
>>>>> Is this just about programmer convenience or is it about space efficiency
>>>>> in
>>>>> the database?  BYTEA might help you.  Or try declaring a DOMAIN over
>>>>> SMALLINT that limits allowed values to the range of a byte. -- Darren
>>>>> Duncan
>>>>
>>>>
>>>> This is purely programmer convenience.
>>>>
>>>> Basically, I want Npgsql to marshal the value as a .NET Byte type, if
>>>> I can find a way to do that I'm happy.  Perhaps it's more of a Npgsql
>>>> question, though I'm curious as to why Postgres doesn't have an
>>>> intrinsic tinyint or byte type.
>>>
>>>
>>> Maybe Postgres doesn't need a Byte type predefined because it gives you the
>>> means to define the type yourself, such as using DOMAIN.
>>>
>>> Generally speaking, I believe it is more important for a type system to
>>> provide the means for arbitrary user-defined types which can be used in all
>>> the places as built-in-defined types, than to have large numbers of
>>> built-in-defined types.
>>
>> Precisely.  postgresql's extensable nature allows you to build your
>> own types as well.  If it's popular enough it'll make it into contrib,
>> then maybe core.  My guess is that there's some non-trivial cost to
>> maintaining each core type, and since a byte type isn't required by
>> the SQL spec, it would take some effort to get a standard one included
>> in the core.
>
> That makes sense.
>
> I guess my question is more of a NpgSql question then.  Is there a way
> to create a custom PG type, and have npgsql serialize that type in a
> dataset to a .NET Byte type?
>
> I'd probably be better off posting on the npgsql mailing list, but
> perhaps someone here knows as well..
>

Hi!

Npgsql already has support to map .Net byte data type to int2 and vice-versa.

You can see all the supported type mappings in this file:
http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/npgsql/Npgsql2/src/NpgsqlTypes/NpgsqlTypesHelper.cs?rev=1.41&content-type=text/x-cvsweb-markup

Check method PrepareDefaultTypesMap().

I hope it helps.

--
Regards,

Francisco Figueiredo Jr.
Npgsql Lead Developer
http://www.npgsql.org
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