postgresql_idx: consider schema name when checking (#693)

When checking to see if an index exists, the schema name needs to be
taken into account.  That is, the same name can exist in multiple
schemas.

Fixes #692

(cherry picked from commit 09fec84)

changelogs/fragments/693-idx-consider-schema.yaml

@@ -0,0 +1,2 @@
+bugfixes:
+  - postgresql_idx - consider schema name when checking for index (https://github.com/ansible-collections/community.postgresql/issues/692).  Index names are only unique within a schema. This allows using the same index name in multiple schemas.

plugins/modules/postgresql_idx.py

@@ -349,9 +349,10 @@ def __exists_in_db(self):
                  "ON i.indexname = c.relname "
                  "JOIN pg_catalog.pg_index AS pi "
                  "ON c.oid = pi.indexrelid "
-                 "WHERE i.indexname = %(name)s")
+                 "WHERE i.schemaname = %(schema)s "
+                 "AND i.indexname = %(name)s")
 
-        res = exec_sql(self, query, query_params={'name': self.name}, add_to_executed=False)
+        res = exec_sql(self, query, query_params={'schema': self.schema, 'name': self.name}, add_to_executed=False)
         if res:
             self.exists = True
             self.info = dict(