Hackers,
I’m doing some development with the new JSON type (actually, Andrew’s backport
to 9.1) and needed to do some very basic equivalence testing. So I created a
custom operator:
CREATE OR REPLACE FUNCTION json_eq(
json,
json
) RETURNS BOOLEAN LANGUAGE SQL STRICT IMMUTABLE AS $$
SELECT $1::text = $2::text;
$$;
CREATE OPERATOR = (
LEFTARG = json,
RIGHTARG = json,
PROCEDURE = json_eq
);
With this in place, these work:
SELECT '{}'::json = '{}'::json;
SELECT ROW('{}'::json) = ROW('{}'::json);
However this does not:
create type ajson AS (a json);
SELECT ROW('{}'::json)::ajson = ROW('{}'::json)::ajson;
That last line emits an error:
ERROR: could not identify an equality operator for type json
To which my response was: WTF? Is this expected behavior? Is there something
about custom operators that they can’t be used to compare the values of values
in composite types?
I’ve worked around it by writing a separate operator to compare ajson types
using
SELECT $1::text = $2::text
But it’s a bit annoying.
Thanks,
David
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