Re: convert custom datatype to array

OK, forgive my ignorance here, but the maintainer of our custom data
type code is no longer with us and this is new territory for me. We do
have a function which takes our custom data type and returns a cstring.
Is there a pg function which converts a cstring to text type? This
seems to be the missing link to eventually get the data to float4[].

Mike

Alvaro Herrera wrote:
> Mike Charnoky wrote:
>> Our database schema was designed before postgresql supported arrays and
>> contains a custom type which is basically a float4 array. I would like
>> to clean things up and convert the custom datatype to float4[], as this
>> would obviate the need for us to compile a custom shared object. We are
>> hitting problems with pg8.3 and I would rather just drop the custom stuff.
>>
>> Problem is, I cannot do an ALTER COLUMN:
>>
>> mydb=# alter table mytable alter column mycolumn float4[];
>> ERROR: column "mycolumn" cannot be cast to type "float4[]"
>
> You can specify a USING clause to let the system know exactly how to
> convert your type to float[]. I suspect you can use float4in() and
> something to read out your type into the format that float4in expects (a
> hacked up version of your out function perhaps).
>