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

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

   137     return ','.join(mainvars)

   137     return ','.join(mainvars)

   138 

   138 

   139 def split_expression(rqlstring):

   139 def split_expression(rqlstring):

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

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

   143 

   144 

   144 def normalize_expression(rqlstring):

   145 def normalize_expression(rqlstring):

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

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

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

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

   147     for instance)

   148     for instance)