Re: [HACKERS] Custom Operators Cannot be Found for Composite Type Values

[David E. Wheeler]

On Mar 7, 2012, at 8:23 PM, Tom Lane wrote:

> You have not told the system that your operator is equality for the
> datatype.  It's just a random operator that happens to be named "=".
> We try to avoid depending on operator names as cues to semantics.
> 
> You need to incorporate it into a default hash or btree opclass before
> the composite-type logic will accept it as the thing to use for
> comparing that column.

Ah, okay. Just need more stuff, I guess:

    CREATE OR REPLACE FUNCTION json_cmp(
        json,
        json
    ) RETURNS INTEGER LANGUAGE SQL STRICT IMMUTABLE AS $$
        SELECT bttextcmp($1::text, $2::text);
    $$;

    CREATE OR REPLACE FUNCTION json_eq(
        json,
        json
    ) RETURNS BOOLEAN LANGUAGE SQL STRICT IMMUTABLE AS $$
        SELECT bttextcmp($1::text, $2::text) = 0;
    $$;

    CREATE OPERATOR = (
        LEFTARG   = json,
        RIGHTARG  = json,
        PROCEDURE = json_eq
    );

    CREATE OPERATOR CLASS json_ops
    DEFAULT FOR TYPE JSON USING btree AS
    OPERATOR    3   =  (json, json),
    FUNCTION    1   json_cmp(json, json);

This seems to work.

Best,

David


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