connector/read/SupportsReportStatistics.java

0001 /*
0002  * Licensed to the Apache Software Foundation (ASF) under one or more
0003  * contributor license agreements.  See the NOTICE file distributed with
0004  * this work for additional information regarding copyright ownership.
0005  * The ASF licenses this file to You under the Apache License, Version 2.0
0006  * (the "License"); you may not use this file except in compliance with
0007  * the License.  You may obtain a copy of the License at
0008  *
0009  *    http://www.apache.org/licenses/LICENSE-2.0
0010  *
0011  * Unless required by applicable law or agreed to in writing, software
0012  * distributed under the License is distributed on an "AS IS" BASIS,
0013  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
0014  * See the License for the specific language governing permissions and
0015  * limitations under the License.
0016  */
0017
0018 package org.apache.spark.sql.connector.read;
0019
0020 import org.apache.spark.annotation.Evolving;
0021
0022 /**
0023  * A mix in interface for {@link Scan}. Data sources can implement this interface to
0024  * report statistics to Spark.
0025  *
0026  * As of Spark 2.4, statistics are reported to the optimizer before any operator is pushed to the
0027  * data source. Implementations that return more accurate statistics based on pushed operators will
0028  * not improve query performance until the planner can push operators before getting stats.
0029  *
0030  * @since 3.0.0
0031  */
0032 @Evolving
0033 public interface SupportsReportStatistics extends Scan {
0034
0035   /**
0036    * Returns the estimated statistics of this data source scan.
0037    */
0038   Statistics estimateStatistics();
0039 }