[GitHub] spark pull request #18975: [SPARK-4131] Support "Writing data into the files...

[xuanyuanking <gi...@git.apache.org>]

Github user xuanyuanking commented on a diff in the pull request:

    https://github.com/apache/spark/pull/18975#discussion_r155185768
  
    --- Diff: sql/core/src/main/scala/org/apache/spark/sql/execution/command/InsertIntoDataSourceDirCommand.scala ---
    @@ -0,0 +1,82 @@
    +/*
    + * 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.execution.command
    +
    +import org.apache.spark.SparkException
    +import org.apache.spark.sql._
    +import org.apache.spark.sql.catalyst.catalog._
    +import org.apache.spark.sql.catalyst.plans.logical.LogicalPlan
    +import org.apache.spark.sql.execution.SparkPlan
    +import org.apache.spark.sql.execution.datasources._
    +
    +/**
    + * A command used to write the result of a query to a directory.
    + *
    + * The syntax of using this command in SQL is:
    + * {{{
    + *   INSERT OVERWRITE DIRECTORY (path=STRING)?
    + *   USING format OPTIONS ([option1_name "option1_value", option2_name "option2_value", ...])
    + *   SELECT ...
    + * }}}
    + *
    + * @param storage storage format used to describe how the query result is stored.
    + * @param provider the data source type to be used
    + * @param query the logical plan representing data to write to
    + * @param overwrite whthere overwrites existing directory
    + */
    +case class InsertIntoDataSourceDirCommand(
    +    storage: CatalogStorageFormat,
    +    provider: String,
    +    query: LogicalPlan,
    +    overwrite: Boolean) extends RunnableCommand {
    +
    +  override def children: Seq[LogicalPlan] = Seq(query)
    +
    +  override def run(sparkSession: SparkSession, children: Seq[SparkPlan]): Seq[Row] = {
    +    assert(children.length == 1)
    +    assert(storage.locationUri.nonEmpty, "Directory path is required")
    +    assert(provider.nonEmpty, "Data source is required")
    +
    +    // Create the relation based on the input logical plan: `query`.
    +    val pathOption = storage.locationUri.map("path" -> CatalogUtils.URIToString(_))
    +
    +    val dataSource = DataSource(
    +      sparkSession,
    +      className = provider,
    +      options = storage.properties ++ pathOption,
    +      catalogTable = None)
    +
    +    val isFileFormat = classOf[FileFormat].isAssignableFrom(dataSource.providingClass)
    +    if (!isFileFormat) {
    +      throw new SparkException(
    +        "Only Data Sources providing FileFormat are supported: " + dataSource.providingClass)
    +    }
    +
    +    val saveMode = if (overwrite) SaveMode.Overwrite else SaveMode.ErrorIfExists
    +    try {
    +      sparkSession.sessionState.executePlan(dataSource.planForWriting(saveMode, query))
    +      dataSource.writeAndRead(saveMode, query)
    --- End diff --
    
    The implementation here confused me, just want to leave a question here why we should call both `writeAndRead` and `planForWriting`?
    @janewangfb @gatorsmile @cloud-fan 


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