* adds it to the given {@link DaoQuery}.
* @param tree
* @param query
*/
private void readCriterion(CommonTree tree, AbstractQueryCriterion<?> query, ExecutionContext ctx) {
DocumentCriterion criterion = null;
String fieldName = null;
switch (tree.getType()) {
case MqlParser.DOCUMENT_FUNCTION_CRITERION:
String functionName = child(tree, 0).getChild(0).getText().trim().toLowerCase();
Criterion c = createCriterion(tree, ctx);