added synonym readme

geocoder/admin0/README.md

@@ -71,4 +71,13 @@ __notes:__
 
 - The column `adm0_a3` will be used as a unique identifier.
 - The ranks are somewhat arbitrarily organized and should be modified later based on our users use of the geocoder (will users more commonly geocode an adm0_a3 or abbreviation?) 
-- I also forgot to assign a `rank` of `2` to a synonym.
+- I also forgot to assign a `rank` of `2` to a synonym.
+
+# Admin0 Synonym Service
+
+If you need to look up the iso code for any list of countries without returning any geometries, you can use the endpoint defined in sql/synonym_service.sql. An example works like this,
+
+```sql
+SELECT (admin0_synonym_lookup(Array['United States', 'ESP'])).*
+```
+

geocoder/admin0/sql/synonym_service.sql

@@ -10,6 +10,6 @@ CREATE OR REPLACE FUNCTION admin0_synonym_lookup(name text[])
   BEGIN
   -- FOR ret IN
   RETURN QUERY
-    SELECT d.q, n.adm0_a3 FROM (SELECT q, lower(regexp_replace(q, '[^a-zA-Z\u00C0-\u00ff]+', '', 'g'))::text x FROM (SELECT unnest(name) q) g) d LEFT OUTER JOIN admin0_synonyms s ON name_ = d.x GROUP BY d.q, n.adm0_a3;
+    SELECT d.q, s.adm0_a3 FROM (SELECT q, lower(regexp_replace(q, '[^a-zA-Z\u00C0-\u00ff]+', '', 'g'))::text x FROM (SELECT unnest(name) q) g) d LEFT OUTER JOIN admin0_synonyms s ON name_ = d.x GROUP BY d.q, s.adm0_a3;
 END
 $$ LANGUAGE 'plpgsql' SECURITY DEFINER;