Re: Proposal: casts row to array and array to row

2011/10/11 Robert Haas <robertmhaas(at)gmail(dot)com>:
> On Tue, Oct 11, 2011 at 4:40 AM, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> wrote:
>> Hello
>>
>> A current limits of dynamic work with row types in PL/pgSQL can be
>> decreased with a possible casts between rows and arrays. Now we have a
>> lot of tools for arrays, and these tools should be used for rows too.
>>
>> postgres=# \d mypoint
>> Composite type "public.mypoint"
>>  Column │  Type   │ Modifiers
>> ────────┼─────────┼───────────
>>  a      │ integer │
>>  b      │ integer │
>>
>> postgres=# select cast(rmypoint '(10,20) as int[]);
>>   array
>> ────────────
>>  {10,20}
>> (1 row)
>>
>> postgres=# select cast(ARRAY[10,20] AS mypoint);
>>  mypoint
>> ─────────
>>  (10,20)
>> (1 row)
>>
>> What do you think about this idea?
>
> Well, a ROW can contain values of different types; an ARRAY can't.

yes, I know - but it should be problem only in few cases - when is not
possible to cast a row field to array field.

This is based on user knowledge - it has to choose a adequate array type

sometimes he can use a numeric or int array, sometimes he have to
select text array. Target type is selected by user, and cast fail when
conversion is not possible.

Pavel

>
> --
> Robert Haas
> EnterpriseDB: http://www.enterprisedb.com
> The Enterprise PostgreSQL Company
>