Github user cloud-fan commented on a diff in the pull request:
https://github.com/apache/spark/pull/16386#discussion_r101684686
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/json/JsonDataSource.scala
---
@@ -0,0 +1,216 @@
+/*
+ * 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.datasources.json
+
+import java.io.InputStream
+
+import scala.reflect.ClassTag
+
+import com.fasterxml.jackson.core.{JsonFactory, JsonParser}
+import com.google.common.io.ByteStreams
+import org.apache.hadoop.conf.Configuration
+import org.apache.hadoop.fs.{FileStatus, Path}
+import org.apache.hadoop.io.{LongWritable, Text}
+import org.apache.hadoop.mapreduce.Job
+import org.apache.hadoop.mapreduce.lib.input.{FileInputFormat,
TextInputFormat}
+
+import org.apache.spark.TaskContext
+import org.apache.spark.input.{PortableDataStream, StreamInputFormat}
+import org.apache.spark.rdd.{BinaryFileRDD, RDD}
+import org.apache.spark.sql.{AnalysisException, SparkSession}
+import org.apache.spark.sql.catalyst.InternalRow
+import org.apache.spark.sql.catalyst.json.{CreateJacksonParser,
JacksonParser, JSONOptions}
+import org.apache.spark.sql.execution.datasources.{CodecStreams,
HadoopFileLinesReader, PartitionedFile}
+import org.apache.spark.sql.types.StructType
+import org.apache.spark.unsafe.types.UTF8String
+import org.apache.spark.util.Utils
+
+/**
+ * Common functions for parsing JSON files
+ * @tparam T A datatype containing the unparsed JSON, such as [[Text]] or
[[String]]
+ */
+abstract class JsonDataSource[T] extends Serializable {
+ def isSplitable: Boolean
+
+ /**
+ * Parse a [[PartitionedFile]] into 0 or more [[InternalRow]] instances
+ */
+ def readFile(
+ conf: Configuration,
+ file: PartitionedFile,
+ parser: JacksonParser): Iterator[InternalRow]
+
+ /**
+ * Create an [[RDD]] that handles the preliminary parsing of [[T]]
records
+ */
+ protected def createBaseRdd(
+ sparkSession: SparkSession,
+ inputPaths: Seq[FileStatus]): RDD[T]
+
+ /**
+ * A generic wrapper to invoke the correct [[JsonFactory]] method to
allocate a [[JsonParser]]
+ * for an instance of [[T]]
+ */
+ def createParser(jsonFactory: JsonFactory, value: T): JsonParser
+
+ final def infer(
+ sparkSession: SparkSession,
+ inputPaths: Seq[FileStatus],
+ parsedOptions: JSONOptions): Option[StructType] = {
+ if (inputPaths.nonEmpty) {
+ val jsonSchema = JsonInferSchema.infer(
+ createBaseRdd(sparkSession, inputPaths),
+ parsedOptions,
+ createParser)
+ checkConstraints(jsonSchema)
+ Some(jsonSchema)
+ } else {
+ None
+ }
+ }
+
+ /** Constraints to be imposed on schema to be stored. */
+ private def checkConstraints(schema: StructType): Unit = {
+ if (schema.fieldNames.length != schema.fieldNames.distinct.length) {
+ val duplicateColumns = schema.fieldNames.groupBy(identity).collect {
+ case (x, ys) if ys.length > 1 => "\"" + x + "\""
+ }.mkString(", ")
+ throw new AnalysisException(s"Duplicate column(s) :
$duplicateColumns found, " +
+ s"cannot save to JSON format")
+ }
+ }
+}
+
+object JsonDataSource {
+ def apply(options: JSONOptions): JsonDataSource[_] = {
+ if (options.wholeFile) {
+ WholeFileJsonDataSource
+ } else {
+ TextInputJsonDataSource
+ }
+ }
+
+ /**
+ * Create a new [[RDD]] via the supplied callback if there is at least
one file to process,
+ * otherwise an [[org.apache.spark.rdd.EmptyRDD]] will be returned.
+ */
+ def createBaseRdd[T : ClassTag](
+ sparkSession: SparkSession,
+ inputPaths: Seq[FileStatus])(
+ fn: (Configuration, String) => RDD[T]): RDD[T] = {
+ val paths = inputPaths.map(_.getPath)
+
+ if (paths.nonEmpty) {
+ val job = Job.getInstance(sparkSession.sessionState.newHadoopConf())
+ FileInputFormat.setInputPaths(job, paths: _*)
+ fn(job.getConfiguration, paths.mkString(","))
+ } else {
+ sparkSession.sparkContext.emptyRDD[T]
+ }
+ }
+}
+
+object TextInputJsonDataSource extends JsonDataSource[Text] {
+ override val isSplitable: Boolean = {
+ // splittable if the underlying source is
+ true
+ }
+
+ override protected def createBaseRdd(
+ sparkSession: SparkSession,
+ inputPaths: Seq[FileStatus]): RDD[Text] = {
+ JsonDataSource.createBaseRdd(sparkSession, inputPaths) {
+ case (conf, name) =>
+ sparkSession.sparkContext.newAPIHadoopRDD(
+ conf,
+ classOf[TextInputFormat],
+ classOf[LongWritable],
+ classOf[Text])
+ .setName(s"JsonLines: $name")
+ .values // get the text column
+ }
+ }
+
+ override def readFile(
+ conf: Configuration,
+ file: PartitionedFile,
+ parser: JacksonParser): Iterator[InternalRow] = {
+ val linesReader = new HadoopFileLinesReader(file, conf)
+ Option(TaskContext.get()).foreach(_.addTaskCompletionListener(_ =>
linesReader.close()))
+ linesReader.flatMap(parser.parse(_, createParser, textToUTF8String))
+ }
+
+ private def textToUTF8String(value: Text): UTF8String = {
+ UTF8String.fromBytes(value.getBytes, 0, value.getLength)
+ }
+
+ override def createParser(jsonFactory: JsonFactory, value: Text):
JsonParser = {
+ CreateJacksonParser.text(jsonFactory, value)
+ }
+}
+
+object WholeFileJsonDataSource extends JsonDataSource[PortableDataStream] {
+ override val isSplitable: Boolean = {
+ false
+ }
+
+ override protected def createBaseRdd(
+ sparkSession: SparkSession,
+ inputPaths: Seq[FileStatus]): RDD[PortableDataStream] = {
+ JsonDataSource.createBaseRdd(sparkSession, inputPaths) {
+ case (conf, name) =>
+ new BinaryFileRDD(
+ sparkSession.sparkContext,
+ classOf[StreamInputFormat],
+ classOf[String],
+ classOf[PortableDataStream],
+ conf,
+ sparkSession.sparkContext.defaultMinPartitions)
+ .setName(s"JsonFile: $name")
--- End diff --
nit:
```
new XXX(
...,
...).setName....
```
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