Re: convert custom datatype to array

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).

--
Alvaro Herrera http://www.amazon.com/gp/registry/5ZYLFMCVHXC
"La tristeza es un muro entre dos jardines" (Khalil Gibran)