135         raise Exception('unable to guess selection variables')

   135         raise Exception('unable to guess selection variables')

   136     return ','.join(mainvars)

   136     return ','.join(mainvars)

   137 

   137 

   138 def split_expression(rqlstring):

   138 def split_expression(rqlstring):

   139     for expr in rqlstring.split(','):

   139     for expr in rqlstring.split(','):

   142 

   143 

   143 def normalize_expression(rqlstring):

   144 def normalize_expression(rqlstring):

   144     """normalize an rql expression to ease schema synchronization (avoid

   145     """normalize an rql expression to ease schema synchronization (avoid

   145     suppressing and reinserting an expression if only a space has been added/removed

   146     suppressing and reinserting an expression if only a space has been added/removed

   146     for instance)

   147     for instance)