core/src/main/java/com/orientechnologies/orient/core/sql/parser/OFunctionCall.java
public boolean canExecuteIndexedFunctionWithoutIndex(OFromClause target, OCommandContext context, OBinaryCompareOperator operator,
      Object right) {
    OSQLFunction function = OSQLEngine.getInstance().getFunction(name.getStringValue());
    if (function instanceof OIndexableSQLFunction) {
      return ((OIndexableSQLFunction) function)
          .canExecuteInline(target, operator, right, context, this.getParams().toArray(new OExpression[] {}));
    }
    return false;
  }
public boolean canExecuteIndexedFunctionWithoutIndex(OFromClause target, OCommandContext context, OBinaryCompareOperator operator,
      Object right) {
    OSQLFunction function = OSQLEngine.getInstance().getFunction(name.getStringValue());
    if (function instanceof OIndexableSQLFunction) {
      return ((OIndexableSQLFunction) function)
          .canExecuteInline(target, operator, right, context, this.getParams().toArray(new OExpression[] {}));
    }
    return false;
  }
tests if current function is an indexed function AND that function can also be executed without using the index

@param target   the query target
@param context  the execution context
@param operator
@param right

@return true if current function is an indexed funciton AND that function can also be executed without using the index, false
otherwise