spark PartitionReader 源码
spark PartitionReader 代码
文件路径：/sql/catalyst/src/main/java/org/apache/spark/sql/connector/read/PartitionReader.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.read;
import java.io.Closeable;
import java.io.IOException;
import org.apache.spark.annotation.Evolving;
import org.apache.spark.sql.connector.metric.CustomTaskMetric;
/**
* A partition reader returned by {@link PartitionReaderFactory#createReader(InputPartition)} or
* {@link PartitionReaderFactory#createColumnarReader(InputPartition)}. It's responsible for
* outputting data for a RDD partition.
* <p>
* Note that, Currently the type `T` can only be {@link org.apache.spark.sql.catalyst.InternalRow}
* for normal data sources, or {@link org.apache.spark.sql.vectorized.ColumnarBatch} for columnar
* data sources(whose {@link PartitionReaderFactory#supportColumnarReads(InputPartition)}
* returns true).
*
* @since 3.0.0
*/
@Evolving
public interface PartitionReader<T> extends Closeable {
/**
* Proceed to next record, returns false if there is no more records.
*
* @throws IOException if failure happens during disk/network IO like reading files.
*/
boolean next() throws IOException;
/**
* Return the current record. This method should return same value until `next` is called.
*/
T get();
/**
* Returns an array of custom task metrics. By default it returns empty array. Note that it is
* not recommended to put heavy logic in this method as it may affect reading performance.
*/
default CustomTaskMetric[] currentMetricsValues() {
CustomTaskMetric[] NO_METRICS = {};
return NO_METRICS;
}
}
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