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From cloud-fan <...@git.apache.org>
Subject [GitHub] spark pull request #20153: [SPARK-22392][SQL] data source v2 columnar batch ...
Date Thu, 11 Jan 2018 13:32:16 GMT
Github user cloud-fan commented on a diff in the pull request:

    https://github.com/apache/spark/pull/20153#discussion_r160958116
  
    --- Diff: sql/core/src/main/java/org/apache/spark/sql/sources/v2/reader/SupportsScanColumnarBatch.java
---
    @@ -0,0 +1,51 @@
    +/*
    + * 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.sources.v2.reader;
    +
    +import java.util.List;
    +
    +import org.apache.spark.annotation.InterfaceStability;
    +import org.apache.spark.sql.Row;
    +import org.apache.spark.sql.vectorized.ColumnarBatch;
    +
    +/**
    + * A mix-in interface for {@link DataSourceV2Reader}. Data source readers can implement
this
    + * interface to output {@link ColumnarBatch} and make the scan faster.
    + */
    +@InterfaceStability.Evolving
    +public interface SupportsScanColumnarBatch extends DataSourceV2Reader {
    +  @Override
    +  default List<ReadTask<Row>> createReadTasks() {
    +    throw new IllegalStateException(
    +      "createReadTasks should not be called with SupportsScanColumnarBatch.");
    +  }
    +
    +  /**
    +   * Similar to {@link DataSourceV2Reader#createReadTasks()}, but returns columnar data
in batches.
    +   */
    +  List<ReadTask<ColumnarBatch>> createBatchReadTasks();
    +
    +  /**
    +   * A safety door for columnar batch reader. It's possible that the implementation can
only support
    +   * some certain columns with certain types. Users can overwrite this method and
    +   * {@link #createReadTasks()} to fallback to normal read path under some conditions.
    +   */
    +  default boolean enableBatchRead() {
    --- End diff --
    
    Yea you can interpret it in this way (read data from columnar storage or row storage),
but we can also interpret it as reading a batch of records at a time or one record at a time.


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