ERROR: operator does not exist: json = json

Erik Rijkers <er@xs4all.nl> writes:

Hi,

Comparison of 2 values of type jsonb is allowed.

Comparison of 2 values of type json gives an error.

That seems like an oversight -- or is it deliberate?

This is because json is just a textual representation, and different
JSON strings can be semantically equal because e.g. whitespace and
object key order is not significant.

Example:

select '42'::json = '{}'::json;
--> ERROR: operator does not exist: json = json

(of course, easily 'solved' by casting but that's not really the
point)

To do a proper comparison you have to parse it into a semantic form,
which is what casting to jsonb does.

Thanks,

Erik Rijkers

- ilmari

On 2022-07-08 Fr 07:57, Dagfinn Ilmari Mannsåker wrote:

Erik Rijkers <er@xs4all.nl> writes:

Hi,

Comparison of 2 values of type jsonb is allowed.

Comparison of 2 values of type json gives an error.

That seems like an oversight -- or is it deliberate?

This is because json is just a textual representation, and different
JSON strings can be semantically equal because e.g. whitespace and
object key order is not significant.

Example:

select '42'::json = '{}'::json;
--> ERROR: operator does not exist: json = json

(of course, easily 'solved' by casting but that's not really the
point)

To do a proper comparison you have to parse it into a semantic form,
which is what casting to jsonb does.

Alternatively, if you really need something like this, try
<https://bitbucket.org/adunstan/jsoncmp/src/master/&gt;

(I should probably update it to mark the functions as parallel safe)

cheers

andrew

--
Andrew Dunstan
EDB: https://www.enterprisedb.com