spark SchemaHelper 源码

spark SchemaHelper 代码

文件路径：/sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/state/SchemaHelper.scala

/*
 * 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.streaming.state

import java.io.StringReader

import org.apache.hadoop.fs.{FSDataInputStream, FSDataOutputStream}

import org.apache.spark.sql.execution.streaming.MetadataVersionUtil
import org.apache.spark.sql.types.StructType
import org.apache.spark.util.Utils

/**
 * Helper classes for reading/writing state schema.
 */
object SchemaHelper {

  sealed trait SchemaReader {
    def read(inputStream: FSDataInputStream): (StructType, StructType)
  }

  object SchemaReader {
    def createSchemaReader(versionStr: String): SchemaReader = {
      val version = MetadataVersionUtil.validateVersion(versionStr,
        StateSchemaCompatibilityChecker.VERSION)
      version match {
        case 1 => new SchemaV1Reader
        case 2 => new SchemaV2Reader
      }
    }
  }

  class SchemaV1Reader extends SchemaReader {
    def read(inputStream: FSDataInputStream): (StructType, StructType) = {
      val keySchemaStr = inputStream.readUTF()
      val valueSchemaStr = inputStream.readUTF()
      (StructType.fromString(keySchemaStr), StructType.fromString(valueSchemaStr))
    }
  }

  class SchemaV2Reader extends SchemaReader {
    def read(inputStream: FSDataInputStream): (StructType, StructType) = {
      val buf = new StringBuilder
      val numKeyChunks = inputStream.readInt()
      (0 until numKeyChunks).foreach(_ => buf.append(inputStream.readUTF()))
      val keySchemaStr = buf.toString()

      buf.clear()
      val numValueChunks = inputStream.readInt()
      (0 until numValueChunks).foreach(_ => buf.append(inputStream.readUTF()))
      val valueSchemaStr = buf.toString()
      (StructType.fromString(keySchemaStr), StructType.fromString(valueSchemaStr))
    }
  }

  trait SchemaWriter {
    val version: Int

    final def write(
        keySchema: StructType,
        valueSchema: StructType,
        outputStream: FSDataOutputStream): Unit = {
      writeVersion(outputStream)
      writeSchema(keySchema, valueSchema, outputStream)
    }

    private def writeVersion(outputStream: FSDataOutputStream): Unit = {
      outputStream.writeUTF(s"v${version}")
    }

    protected def writeSchema(
        keySchema: StructType,
        valueSchema: StructType,
        outputStream: FSDataOutputStream): Unit
  }

  object SchemaWriter {
    def createSchemaWriter(version: Int): SchemaWriter = {
      version match {
        case 1 if Utils.isTesting => new SchemaV1Writer
        case 2 => new SchemaV2Writer
      }
    }
  }

  class SchemaV1Writer extends SchemaWriter {
    val version: Int = 1

    def writeSchema(
        keySchema: StructType,
        valueSchema: StructType,
        outputStream: FSDataOutputStream): Unit = {
      outputStream.writeUTF(keySchema.json)
      outputStream.writeUTF(valueSchema.json)
    }
  }

  class SchemaV2Writer extends SchemaWriter {
    val version: Int = 2

    // 2^16 - 1 bytes
    final val MAX_UTF_CHUNK_SIZE = 65535

    def writeSchema(
        keySchema: StructType,
        valueSchema: StructType,
        outputStream: FSDataOutputStream): Unit = {
      val buf = new Array[Char](MAX_UTF_CHUNK_SIZE)

      // DataOutputStream.writeUTF can't write a string at once
      // if the size exceeds 65535 (2^16 - 1) bytes.
      // So a key as well as a value consist of multiple chunks in schema version 2.
      val keySchemaJson = keySchema.json
      val numKeyChunks = (keySchemaJson.length - 1) / MAX_UTF_CHUNK_SIZE + 1
      val keyStringReader = new StringReader(keySchemaJson)
      outputStream.writeInt(numKeyChunks)
      (0 until numKeyChunks).foreach { _ =>
        val numRead = keyStringReader.read(buf, 0, MAX_UTF_CHUNK_SIZE)
        outputStream.writeUTF(new String(buf, 0, numRead))
      }

      val valueSchemaJson = valueSchema.json
      val numValueChunks = (valueSchemaJson.length - 1) / MAX_UTF_CHUNK_SIZE + 1
      val valueStringReader = new StringReader(valueSchemaJson)
      outputStream.writeInt(numValueChunks)
      (0 until numValueChunks).foreach { _ =>
        val numRead = valueStringReader.read(buf, 0, MAX_UTF_CHUNK_SIZE)
        outputStream.writeUTF(new String(buf, 0, numRead))
      }
    }
  }
}

相关信息

spark 源码目录

相关文章

spark FlatMapGroupsWithStateExecHelper 源码

spark HDFSBackedStateStoreMap 源码

spark HDFSBackedStateStoreProvider 源码

spark RocksDB 源码

spark RocksDBFileManager 源码

spark RocksDBLoader 源码

spark RocksDBStateEncoder 源码

spark RocksDBStateStoreProvider 源码

spark StateSchemaCompatibilityChecker 源码

spark StateStore 源码