add code to create json equality operator; #20

Author: mla

contrib/add_json_equality_operator.sql

@@ -0,0 +1,59 @@
+/*
+  If you receive errors about "could not identify an equality operator
+  for type json" and you cannot or do not want to convert the column type
+  from json to jsonb, you can try applying this file. It adds equality
+  operator support for the json type.
+
+  See also https://github.com/mla/pg_sample/issues/20
+*/
+
+create function json_lt(json, json)
+returns boolean language sql immutable as $$
+    select $1::jsonb < $2::jsonb
+$$;
+
+create function json_lte(json, json)
+returns boolean language sql immutable as $$
+    select $1::jsonb < $2::jsonb OR $1::jsonb = $2::jsonb
+$$;
+
+create function json_gt(json, json)
+returns boolean language sql immutable as $$
+    select $1::jsonb > $2::jsonb
+$$;
+
+create function json_gte(json, json)
+returns boolean language sql immutable as $$
+    select $1::jsonb > $2::jsonb OR $1::jsonb = $2::jsonb
+$$;
+
+create function json_eq(json, json)
+returns boolean language sql immutable as $$
+    select $1::jsonb = $2::jsonb
+$$;
+
+
+create operator < (leftarg = json, rightarg = json, procedure = json_lt);
+create operator > (leftarg = json, rightarg = json, procedure = json_gt);
+create operator >= (leftarg = json, rightarg = json, procedure = json_gte);
+create operator <= (leftarg = json, rightarg = json, procedure = json_lte);
+create operator = (leftarg = json, rightarg = json, procedure = json_eq);
+
+create function jsoncmp(json, json)
+returns integer language sql immutable as $$
+    select case 
+        when $1 = $2 then 0
+        when $1 < $2 then -1
+        else 1
+    end
+$$;
+
+create operator class json_ops
+  default for type json using btree AS
+    operator 1 <,
+    operator 2 <=,
+    operator 3 =,
+    operator 4 >=,
+    operator 5 >,
+    function 1 jsoncmp(json, json)
+;