operator is only a shell - Error

Hi,

I wanted to implement a new "=" (equal) operator with LEFTARG as numeric
and RIGHTARG as varchar.  But after creating the function and operator,
psql shows the error "operator is only a shell: character varying =
numeric LINE 1: ...lect LIEN_AC_NO from deposit_lien where
deposit_no='00021140...". I'm sharing the function and operator scripts
for your perusal. Please advise how to proceed.

CREATE OR REPLACE FUNCTION public.num_eq_varchar(
    numeric,
    varchar)
    RETURNS boolean
AS 'select $1::NUMERIC=CAST($2 AS numeric);'
LANGUAGE SQL IMMUTABLE;

-- Operator: =;

-- DROP OPERATOR IF EXISTS public.= (numeric , varchar);

CREATE OPERATOR public.= (
    FUNCTION = num_eq_varchar,
    LEFTARG = numeric,
    RIGHTARG = varchar,
    COMMUTATOR = =,
    NEGATOR = <>,
    RESTRICT = eqsel,
    JOIN = eqjoinsel,
    HASHES, MERGES
);

CREATE OR REPLACE FUNCTION public.num_ne_varchar(
    numeric,
    varchar)
    RETURNS boolean
    LANGUAGE SQL IMMUTABLE
AS $BODY$
    select $1<>$2::numeric;
$BODY$;

-- Operator: <>;

-- DROP OPERATOR IF EXISTS public.<> (numeric , varchar);

CREATE OPERATOR public.<> (
    FUNCTION = num_ne_varchar,
    LEFTARG = numeric,
    RIGHTARG = varchar,
    COMMUTATOR = <>,
    NEGATOR = =,
    RESTRICT = neqsel,
    JOIN = neqjoinsel
);

Thanks,

Rajesh S

On 05-07-2022 13:52, Rajesh S wrote:
>
> Hi,
>
> We are migrating our database from Oracle to Postgresql.  In oracle we
> have used this syntax "SELECT ('1999-12-30'::DATE) -
> ('1999-12-11'::DATE)" to get difference between two dates as a integer
> output (ex: 19).  But in Postgres the same query returns result as "19
> days".  Because of this we are getting errors while assigning this
> query output to a numeric variable saying "ERROR: invalid input syntax
> for type numeric: "1825 days"" and "ERROR: operator does not exist:
> interval + integer".  To avoid changing the application code in many
> places to extract the number of days alone, we tried operator
> overloading concept as below.
>
> CREATE OR REPLACE FUNCTION public.dt_minus_dt(
>     dt1 timestamp without time zone,
>     dt2 timestamp without time zone)
>     RETURNS integer
>     LANGUAGE 'edbspl'
>     COST 100
>     VOLATILE SECURITY DEFINER PARALLEL UNSAFE
> AS $BODY$
>     days INTEGER;
> BEGIN
>     SELECT DATE_PART('day', dt1::timestamp - dt2::timestamp)::integer
> INTO days;
>     RETURN days;
> END
> $BODY$;
>
> CREATE OPERATOR public.- (
>     FUNCTION = public.dt_minus_dt,
>     LEFTARG = timestamp without time zone,
>     RIGHTARG = timestamp without time zone
> );
>
> When we execute "SELECT ('1999-12-30'::DATE) - ('1999-12-11'::DATE)",
> we are still getting "19 days" as result and not "19" as we expect. 
> The above same function works as expected for the operator + or ===.
>
> CREATE OPERATOR public.+ (
>     FUNCTION = public.dt_minus_dt,
>     LEFTARG = timestamp without time zone,
>     RIGHTARG = timestamp without time zone
> );
>
> SELECT ('1999-12-30'::DATE) + ('1999-12-11'::DATE)
>
> CREATE OPERATOR public.=== (
>     FUNCTION = public.dt_minus_dt,
>     LEFTARG = timestamp without time zone,
>     RIGHTARG = timestamp without time zone
> );
>
> SELECT ('1999-12-30'::DATE) === ('1999-12-11'::DATE)
>
>
> I really appreciate anyone's help in resolving this case. Thanks in
> advance.
>
>
> Rajesh S
>
>