From: Tom Lane <tgl@sss.pgh.pa.us>
To: Wells Oliver <wells.oliver@gmail.com>
cc: pgsql-admin <pgsql-admin@postgresql.org>
Subject: Re: Casting json (or jsonb) to real
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Comments: In-reply-to Wells Oliver <wells.oliver@gmail.com>
	message dated "Tue, 31 May 2022 17:31:26 -0700"
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Date: Tue, 31 May 2022 20:50:51 -0400
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Wells Oliver <wells.oliver@gmail.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