Wildcard query expansion resulted in too many terms

I am receiving a "wildcard query expansion resulted in too many terms" error when executing a query similar to the following:

SELECT *
  FROM table_a
 WHERE contains(clo开发者_如何学JAVAb_field, '%a%') > 0;

Does anyone know a workaround/solution to this problem?

According to this, you may need to increase the wildcard_maxterms parameter, or take further steps. See the link for details (I'm not an expert in Oracle Text though).