spark Expression 源码
spark Expression 代码
文件路径：/sql/catalyst/src/main/java/org/apache/spark/sql/connector/expressions/Expression.java
/*
* 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.
*/
package org.apache.spark.sql.connector.expressions;
import java.util.Collections;
import java.util.HashSet;
import java.util.Set;
import org.apache.spark.annotation.Evolving;
/**
* Base class of the public logical expression API.
*
* @since 3.0.0
*/
@Evolving
public interface Expression {
Expression[] EMPTY_EXPRESSION = new Expression[0];
/**
* `EMPTY_EXPRESSION` is only used as an input when the
* default `references` method builds the result array to avoid
* repeatedly allocating an empty array.
*/
NamedReference[] EMPTY_NAMED_REFERENCE = new NamedReference[0];
/**
* Format the expression as a human readable SQL-like string.
*/
default String describe() { return this.toString(); }
/**
* Returns an array of the children of this node. Children should not change.
*/
Expression[] children();
/**
* List of fields or columns that are referenced by this expression.
*/
default NamedReference[] references() {
// SPARK-40398: Replace `Arrays.stream()...distinct()`
// to this for perf gain, the result order is not important.
Set<NamedReference> set = new HashSet<>();
for (Expression e : children()) {
Collections.addAll(set, e.references());
}
return set.toArray(EMPTY_NAMED_REFERENCE);
}
}
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