code: def find_by_index(self, cls, index_name, value):
          
          cur = self._conn().cursor()
  
          # psycopg2 supports using Python formatters for queries
          # we also request our JSON as a string for the from_data calls
          query = 'select id, value::text from {0} where {1} = %s;'.format(
              cls.get_table_name(),
              index_name
          )
  
          found = []
          with self._conn() as conn:
              with conn.cursor() as cur:
                  cur.execute(query, (value,))
                  for row in cur:
                      id, data = str(row[0]).strip(), row[1]
                      obj = cls.from_data(data)
                      assert id == obj.id
                      found.append(obj)
  
          return found
docs: Find all rows matching index query - as per the gludb spec.