public function getSearchExpression($fields, $keywords)
{
if (strlen(trim($keywords)) == 0) {
return '';
}
$words = preg_split('/\\s/u', $keywords);
$conditions = array();
foreach ($fields as $field) {
$column = $this->getTableInfo()->getColumn($field)->getColumnName();
$conditions[] = $this->getSearchCondition($column, $words);
}
return '(' . implode(' OR ', $conditions) . ')';
}