Re: Casting json (or jsonb) to real

Sorry, of course, the correct SQL throwing the error is:

select '"1.453"'::jsonb::real;

On Tue, May 31, 2022 at 6:08 PM Wells Oliver <wells(dot)oliver(at)gmail(dot)com> wrote:

> Well, it's because the representation of the value is getting double
> quoted, so it's
>
> select '"1.453"'::real, which yields ERROR: cannot cast jsonb string to
> type real.
>
> I have all this serialized string data stored in the jsonb col, all of
> which is double quoted.
>
> On Tue, May 31, 2022 at 5:50 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
>> Wells Oliver <wells(dot)oliver(at)gmail(dot)com> writes:
>> > When I know this value is a floating point value I would just like to
>> cast
>> > SELECT value::real but you can't do that. You can do SELECT
>> > (jsonbcol->>'somekey')::real, but these columns just store a value.
>>
>> Works for me, in v11 and up:
>>
>> regression=# select '1.4531'::jsonb::real;
>> float4
>> --------
>> 1.4531
>> (1 row)
>>
>> In older versions you could do
>>
>> regression=# select '1.4531'::jsonb::text::real;
>> float4
>> --------
>> 1.4531
>> (1 row)
>>
>> I fear that either one involves a conversion to text and back
>> under the hood :-(. Now, if you were casting to numeric,
>> that would be very cheap.
>>
>> regards, tom lane
>>
>
>
> --
> Wells Oliver
> wells(dot)oliver(at)gmail(dot)com <wellsoliver(at)gmail(dot)com>
>

--
Wells Oliver
wells(dot)oliver(at)gmail(dot)com <wellsoliver(at)gmail(dot)com>