/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/**
* Logical expression tree representation.
*
* Drill manages expressions provided in many different parts of SQL queries.
* This includes scalar expressions in select, filter and join conditions, as
* well as aggregate and window functions. These expressions are represented
* logically as ASTs during planning. The classes defined here provide the
* different nodes in the expression tree, as well as utilities for building
* and manipulating expressions during parsing and planning.
*
*/
package org.apache.drill.common.expression;