Re: overloading LIKE operator to handle integer + text

> -----Original Message-----
> From: pgsql-general-owner(at)postgresql(dot)org [mailto:pgsql-general-
> owner(at)postgresql(dot)org] On Behalf Of Thalis Kalfigkopoulos
> Sent: Tuesday, October 30, 2012 3:55 PM
> To: pgsql-general(at)postgresql(dot)org
> Subject: [GENERAL] overloading LIKE operator to handle integer + text
>
> Hi all,
>
> I'd like to be able to operate LIKE using as arguments an integer and a
text
> value.
>
> In postgresql 9.0 the following raises an error:
> # SELECT 123 LIKE '123';
> ERROR: operator does not exist: integer ~~ unknown
> LINE 1: select 123 like '123'; ^
> HINT: No operator matches the given name and argument type(s). You
> might need to add explicit type casts.
>
> This can be easily solved as the HINT suggests as:
> # SELECT 123::text LIKE '123';
>
> But I cannot touch the SQL queries generated by the application, which
> generates queries like:
> SELECT * from tabname WHERE "id" LIKE '%34%';
>
> Thus I thought I might overload the LIKE operator to be able to handle the
> case where args are integer and text.
>
> So I create a function:
> CREATE OR REPLACE FUNCTION public.my_like(leftop integer, rightop text)
> RETURNS boolean LANGUAGE sql AS $function$ SELECT $1::text LIKE $2;
> $function$
>
> But then I can't create the operator:
> # CREATE OPERATOR "LIKE" (LEFTARG=integer, RIGHTARG=text,
> PROCEDURE=my_like);
> ERROR: syntax error at or near "("
> LINE 1: CREATE OPERATOR "LIKE" (LEFTARG=integer, RIGHTARG=text,
> PROC...
>
> Any ideas what I'm missing? The doc's examples have a "(".
>
> TIA,
> Thalis K.
>

"LIKE" is apparently not an operator but a special SQL construct. However,
from the error message it appears that internally LIKE is transformed to the
~~ operator (which is defined as being equivalent). You should try
overloading the ~~ operator (and probably the NOT version equivalents - see
section 9.7.1 in the PostgreSQL 9.2 documentation) and see if that works.

David J.