Re: Casting json (or jsonb) to real

[Wells Oliver <wells.oliver@xxxxxxxxx>]

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.oliver@xxxxxxxxx> 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@xxxxxxxxxxxxx> wrote:

Wells Oliver <wells.oliver@xxxxxxxxx> 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.oliver@xxxxxxxxx

--

Wells Oliver
wells.oliver@xxxxxxxxx