spark-sql架构与原理

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spark-sql架构与原理
一. 整体架构

总结为如下图：

Dataframe本质是数据 + 数据的描述信息（结构元信息）

所有的上述SQL及dataframe操作最终都通过Catalyst翻译成spark程序RDD操作代码

sparkSQL前身是shark，大量依赖Hive项目的jar包与功能，但在上面的扩展越来越难，因此出现了SparkSQL，它重写了分析器，执行器 脱离了对Hive项目的大部分依赖，基本可以独立去运行，只用到两个地方：

1.借用了hive的词汇分析的jar即HiveQL解析器

2.借用了hive的metastore和数据访问API即hiveCatalog

也就是说上图的左半部分的操作全部用的是sparkSQL本身自带的内置SQL解析器解析SQL进行翻译，用到内置元数据信息(比如结构化文件中自带的结构元信息，RDD的schema中的结构元信息)

右半部分则是走的Hive的HQL解析器，还有Hive元数据信息

因此左右两边的API调用的底层类会有不同

SQLContext使用：

简单的解析器（scala语言写的sql解析器）【比如：1.在半结构化的文件里面使用sql查询时，是用这个解析器解析的，2.访问（半）结构化文件的时候，通过sqlContext使用schema，类生成Dataframe，然后dataframe注册为表时，registAsTmpTable 然后从这个表里面进行查询时，即使用的简单的解析器，一些hive语法应该是不支持的，有待验证）】

simpleCatalog【此对象中存放关系（表），比如我们指定的schema信息，类的信息，都是关系信息】

HiveContext使用：

HiveQL解析器【支持hive的hql语法，如只有通过HiveContext生成的dataframe才能调用saveAsTable操作】

hiveCatalog（存放数据库和表的元数据信息）

Sparksql的解析与Hiveql的解析的执行流程:

一个Sql语句转化为实际可执行的Spark的RDD模型需要经过以下几个步骤：

主要介绍下Spark-SQL里面的主要类成员：

1.2 SQLContext

SQL上下文环境，它保存了QueryExecution中所需要的几个类：

1.2.1 Catalog
一个存储<tableName,logicalPlan>的map结构，查找关系的目录，注册表，注销表，查询表和逻辑计划关系的类

[java] view plain copy

@transient
protected[sql] lazy val catalog: Catalog = new SimpleCatalog(conf)
class SimpleCatalog(val conf: CatalystConf) extends Catalog {
  val tables = new mutable.HashMap[String, LogicalPlan]()
  override def registerTable(
      tableIdentifier: Seq[String],
      plan: LogicalPlan): Unit = {
    //转化大小写
    val tableIdent = processTableIdentifier(tableIdentifier)
    tables += ((getDbTableName(tableIdent), plan))
  }
  override def unregisterTable(tableIdentifier: Seq[String]): Unit = {
    val tableIdent = processTableIdentifier(tableIdentifier)
    tables -= getDbTableName(tableIdent)
  }
  override def unregisterAllTables(): Unit = {
    tables.clear()
  }
  override def tableExists(tableIdentifier: Seq[String]): Boolean = {
    val tableIdent = processTableIdentifier(tableIdentifier)
    tables.get(getDbTableName(tableIdent)) match {
      case Some(_) => true
      case None => false
    }
  }
  override def lookupRelation(
      tableIdentifier: Seq[String],
      alias: Option[String] = None): LogicalPlan = {
    val tableIdent = processTableIdentifier(tableIdentifier)
    val tableFullName = getDbTableName(tableIdent)
    //  val tables = new mutable.HashMap[String, LogicalPlan](),根据表名获取logicalplan
    val table = tables.getOrElse(tableFullName, sys.error(s"Table Not Found: $tableFullName"))
    val tableWithQualifiers = Subquery(tableIdent.last, table)
    // If an alias was specified by the lookup, wrap the plan in a subquery so that attributes are
    // properly qualified with this alias.
    alias.map(a => Subquery(a, tableWithQualifiers)).getOrElse(tableWithQualifiers)
  }
  override def getTables(databaseName: Option[String]): Seq[(String, Boolean)] = {
    tables.map {
      case (name, _) => (name, true)
    }.toSeq
  }
  override def refreshTable(databaseName: String, tableName: String): Unit = {
    throw new UnsupportedOperationException
  }
}

1.2.2 SparkSQLParser
将Sql语句解析成语法树，返回一个Logical Plan。它首先拆分不同的SQL（将其分类），然后利用fallback解析。
[java] view plain copy

/**
* The top level Spark SQL parser. This parser recognizes syntaxes that are available for all SQL
* dialects supported by Spark SQL, and delegates all the other syntaxes to the `fallback` parser.
*
* @param fallback A function that parses an input string to a logical plan
*/
private[sql] class SparkSQLParser(fallback: String => LogicalPlan) extends AbstractSparkSQLParser {
protected val AS = Keyword("AS")
protected val CACHE = Keyword("CACHE")
protected val CLEAR = Keyword("CLEAR")
protected val IN = Keyword("IN")
protected val LAZY = Keyword("LAZY")
protected val SET = Keyword("SET")
protected val SHOW = Keyword("SHOW")
protected val TABLE = Keyword("TABLE")
protected val TABLES = Keyword("TABLES")
protected val UNCACHE = Keyword("UNCACHE")
override protected lazy val start: Parser[LogicalPlan] = cache | uncache | set | show | others
private lazy val cache: Parser[LogicalPlan] =
  CACHE ~> LAZY.? ~ (TABLE ~> ident) ~ (AS ~> restInput).? ^^ {
    case isLazy ~ tableName ~ plan =>
      CacheTableCommand(tableName, plan.map(fallback), isLazy.isDefined)
  }
private lazy val uncache: Parser[LogicalPlan] =
  ( UNCACHE ~ TABLE ~> ident ^^ {
      case tableName => UncacheTableCommand(tableName)
    }
  | CLEAR ~ CACHE ^^^ ClearCacheCommand
  )
private lazy val set: Parser[LogicalPlan] =
  SET ~> restInput ^^ {
    case input => SetCommandParser(input)
  }
private lazy val show: Parser[LogicalPlan] =
  SHOW ~> TABLES ~ (IN ~> ident).? ^^ {
    case _ ~ dbName => ShowTablesCommand(dbName)
  }
private lazy val others: Parser[LogicalPlan] =
  wholeInput ^^ {
    case input => fallback(input)
  }
}
1.2.3 Analyzer

语法分析器，Analyzer会使用Catalog和FunctionRegistry将UnresolvedAttribute和UnresolvedRelation转换为catalyst里全类型的对象。例如将

'UnresolvedRelation[test], None

转化为

Relation[id#0L,dev_id#1,dev_chnnum#2L,dev_name#3,dev_chnname#4,car_num#5,car_numtype#6,car_numcolor#7,car_speed#8,car_type#9,car_color#10,car_length#11L,car_direct#12,car_way_code#13,cap_time#14L,cap_date#15L,inf_note#16,max_speed#17,min_speed#18,car_img_url#19,car_img1_url#20,car_img2_url#21,car_img3_url#22,car_img4_url#23,car_img5_url#24,rec_stat#25,dev_chnid#26,car_img_count#27,save_flag#28,dc_cleanflag#29,pic_id#30,car_img_plate_top#31L,car_img_plate_left#32L,car_img_plate_bottom#33L,car_img_plate_right#34L,car_brand#35L,issafetybelt#36,isvisor#37,bind_stat#38,car_num_pic#39,combined_pic_url#40,verify_memo#41,rec_stat_tmp#42]org.apache.spark.sql.parquet.ParquetRelation2@2a400010
[java] view plain copy

class Analyzer(
    catalog: Catalog,
    registry: FunctionRegistry,
    conf: CatalystConf,
    maxIterations: Int = 100)
  extends RuleExecutor[LogicalPlan] with HiveTypeCoercion with CheckAnalysis {
……
}
1.2.4 Optimizer

优化器，将Logical Plan进一步进行优化
[java] view plain copy

object DefaultOptimizer extends Optimizer {
  val batches =
    // SubQueries are only needed for analysis and can be removed before execution.
    Batch("Remove SubQueries", FixedPoint(100),
      EliminateSubQueries) ::
    Batch("Operator Reordering", FixedPoint(100),
      UnionPushdown,
      CombineFilters,
      PushPredicateThroughProject,
      PushPredicateThroughJoin,
      PushPredicateThroughGenerate,
      ColumnPruning,
      ProjectCollapsing,
      CombineLimits) ::
    Batch("ConstantFolding", FixedPoint(100),
    NullPropagation,
      OptimizeIn,
      ConstantFolding,
      LikeSimplification,
      BooleanSimplification,
      SimplifyFilters,
      SimplifyCasts,
      SimplifyCaseConversionExpressions) ::
    Batch("Decimal Optimizations", FixedPoint(100),
      DecimalAggregates) ::
    Batch("LocalRelation", FixedPoint(100),
      ConvertToLocalRelation) :: Nil
}
例如:
CombineFilters:递归合并两个相邻的filter。例如：将

Filter(a>1)

Filter(b>1)

Project……

转化为

Filter(a>1) AND Filter(b>1)

Project……
```
CombineLimits:合并两个相邻的limit。例如：将select * from (select * from c_picrecord limit 100)a limit 10
```
优化为：

Limit if ((100 < 10)) 100 else 10
Relation[id#0L,dev_id#1,dev_chnnum#2L,de……

1.2.5 SparkPlanner

将LogicalPlan转化为SparkPlan
[java] view plain copy

protected[sql] class SparkPlanner extends SparkStrategies {
  val sparkContext: SparkContext = self.sparkContext
  val sqlContext: SQLContext = self
  def codegenEnabled: Boolean = self.conf.codegenEnabled
  def unsafeEnabled: Boolean = self.conf.unsafeEnabled
  def numPartitions: Int = self.conf.numShufflePartitions
  def strategies: Seq[Strategy] =
    experimental.extraStrategies ++ (
    DataSourceStrategy ::
    DDLStrategy ::
    TakeOrdered ::
    HashAggregation ::
    LeftSemiJoin ::
    HashJoin ::
    InMemoryScans ::
      ParquetOperations ::
      BasicOperators ::
      CartesianProduct ::
      BroadcastNestedLoopJoin :: Nil)
}
比方说：

Subquery test

Relation[id#0L,dev_id#1,dev_chnnum#2L,dev_name#3,dev_chnname#4,car_num#5,car_numtype#6,car_numcolor#7,car_speed#8,car_type#9,car_color#10,car_length#11L,car_direct#12,car_way_code#13,cap_time#14L,cap_date#15L,inf_note#16,max_speed#17,min_speed#18,car_img_url#19,car_img1_url#20,car_img2_url#21,car_img3_url#22,car_img4_url#23,car_img5_url#24,rec_stat#25,dev_chnid#26,car_img_count#27,save_flag#28,dc_cleanflag#29,pic_id#30,car_img_plate_top#31L,car_img_plate_left#32L,car_img_plate_bottom#33L,car_img_plate_right#34L,car_brand#35L,issafetybelt#36,isvisor#37,bind_stat#38,car_num_pic#39,combined_pic_url#40,verify_memo#41,rec_stat_tmp#42]org.apache.spark.sql.parquet.ParquetRelation2@2a400010
```
通过DataSourceStrategy中的
```
```
[java] view plain copy
 
// Scanning non-partitioned HadoopFsRelation  
case PhysicalOperation(projectList, filters, l @ LogicalRelation(t: HadoopFsRelation)) =>  
```
```
将其转化为
PhysicalRDD
```
1.2.6 PrepareForExecution
```
在SparkPlan中插入Shuffle的操作，如果前后2个SparkPlan的outputPartitioning不一样的话，则中间需要插入Shuffle的动作，比分说聚合函数，先局部聚合，然后全局聚合，局部聚合和全局聚合的分区规则是不一样的，中间需要进行一次Shuffle。
```
```
[java] view plain copy
 
/** 
 * Prepares a planned SparkPlan for execution by inserting shuffle operations as needed. 
 */  
@transient  
protected[sql] val prepareForExecution = new RuleExecutor[SparkPlan] {  
  val batches =  
    Batch("Add exchange", Once, EnsureRequirements(self)) :: Nil  
}  
例如
```
GeneratedAggregate false,[Coalesce(SUM(PartialCount#44L),0) AS count#43L], false

GeneratedAggregatetrue, [COUNT(1) AS PartialCount#44L], false

PhysicalRDDMapPartitionsRDD[1]

经过PrepareForExecution，转化为

GeneratedAggregate false,[Coalesce(SUM(PartialCount#44L),0) AS count#43L], false

Exchange SinglePartition

GeneratedAggregate true, [COUNT(1) AS PartialCount#44L], false

PhysicalRDDMapPartitionsRDD[1]

1.3 QueryExecution

SQL语句执行环境
[java] view plain copy

protected[sql] class QueryExecution(val logical: LogicalPlan) {//logical包含了Aggregate(groupingExprs, aggregates, df.logicalPlan)
  def assertAnalyzed(): Unit = analyzer.checkAnalysis(analyzed)
  lazy val analyzed: LogicalPlan = analyzer.execute(logical)
  lazy val withCachedData: LogicalPlan = {
    assertAnalyzed()
    cacheManager.useCachedData(analyzed)
  }
  lazy val optimizedPlan: LogicalPlan = optimizer.execute(withCachedData)//优化过的LogicalPlan
  // TODO: Don't just pick the first one...
  lazy val sparkPlan: SparkPlan = {
    SparkPlan.currentContext.set(self)
    //SparkPlanner把LogicalPlan转化为SparkPlan
    //1.4.1选取的是第一个strategies DataSourceStrategy
    planner.plan(optimizedPlan).next()
  }
  lazy val executedPlan: SparkPlan = prepareForExecution.execute(sparkPlan)
  lazy val toRdd: RDD[Row] = {
    toString
    executedPlan.execute()
  }
  protected def stringOrError[A](f: => A): String =
    try f.toString catch { case e: Throwable => e.toString }
  def simpleString: String =
    s"""== Physical Plan ==
       |${stringOrError(executedPlan)}
    """.stripMargin.trim
  //TODO:如何打印
  override def toString: String = {
    def output =
      analyzed.output.map(o => s"${o.name}: ${o.dataType.simpleString}").mkString(", ")
    // TODO previously will output RDD details by run (${stringOrError(toRdd.toDebugString)})
    // however, the `toRdd` will cause the real execution, which is not what we want.
    // We need to think about how to avoid the side effect.
    s"""== Parsed Logical Plan ==
       |${stringOrError(logical)}
       |== Analyzed Logical Plan ==
       |${stringOrError(output)}
       |${stringOrError(analyzed)}
       |== Optimized Logical Plan ==
       |${stringOrError(optimizedPlan)}
       |== Physical Plan ==
       |${stringOrError(executedPlan)}
       |Code Generation: ${stringOrError(executedPlan.codegenEnabled)}
       |== RDD ==
    """.stripMargin.trim
  }
}
这里唯一需要注意的是analyzed，optimizedPlan，sparkPlan，executedPlan都为懒变量，也就是说只有真正要用到的时时候才会去执行相应的代码逻辑，没有用到的时候是不会发生任何事情的。

1.4 LogicalPlan and SparkPlan

LogicalPlan和SparkPlan都继承自QueryPlan，QueryPlan为泛型类
[java] view plain copy

abstract class QueryPlan[PlanType <: TreeNode[PlanType]] extends TreeNode[PlanType] {
}
abstract class LogicalPlan extends QueryPlan[LogicalPlan] with Logging {
}
abstract class SparkPlan extends QueryPlan[SparkPlan] with Logging with Serializable {
}
以上都为抽象类，然后在此基础上又根据不同的类型衍生出不同的树节点
[java] view plain copy

/**
* A logical plan node with no children.叶子节点，没有子节点
*/
abstract class LeafNode extends LogicalPlan with trees.LeafNode[LogicalPlan] {
  self: Product =>
}
/**
* A logical plan node with single child. 一元节点
*/
abstract class UnaryNode extends LogicalPlan with trees.UnaryNode[LogicalPlan] {
  self: Product =>
}
/**
* A logical plan node with a left and right child 二元节点.
*/
abstract class BinaryNode extends LogicalPlan with trees.BinaryNode[LogicalPlan] {
  self: Product =>
}
[java] view plain copy

//叶子节点，没有子节点
private[sql] trait LeafNode extends SparkPlan with trees.LeafNode[SparkPlan] {
  self: Product =>
}
//一元节点
private[sql] trait UnaryNode extends SparkPlan with trees.UnaryNode[SparkPlan] {
  self: Product =>
}
//二元节点
private[sql] trait BinaryNode extends SparkPlan with trees.BinaryNode[SparkPlan] {
  self: Product =>
}
其各自真正的具体类为：
[java] view plain copy

abstract class LeafNode extends LogicalPlan with trees.LeafNode[LogicalPlan] {
  self: Product =>
}
[java] view plain copy

abstract class UnaryNode extends LogicalPlan with trees.UnaryNode[LogicalPlan] {
  self: Product =>
}
[java] view plain copy

abstract class BinaryNode extends LogicalPlan with trees.BinaryNode[LogicalPlan] {
  self: Product =>
}
[java] view plain copy

private[sql] trait LeafNode extends SparkPlan with trees.LeafNode[SparkPlan] {
  self: Product =>
}
[java] view plain copy

private[sql] trait UnaryNode extends SparkPlan with trees.UnaryNode[SparkPlan] {
  self: Product =>
}
[java] view plain copy

private[sql] trait BinaryNode extends SparkPlan with trees.BinaryNode[SparkPlan] {
  self: Product =>
}
可见Spark-Sql里面二叉树结构贯穿了整个解析过程。

二. Catalyst

所有的SQL操作最终都通过Catalyst翻译成spark程序代码

三. SparkSQL整体架构（前端+后端）

thriftserver作为一个前端，它其实只是主要分为两大块：

1.维护与用户的JDBC连接

2.通过HiveContext的API提交用户的HQL查询
正因为当初对未来做了太多的憧憬，所以对现在的自己尤其失望。生命中曾经有过的所有灿烂，终究都需要用寂寞来偿还。
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原文地址：https://www.cnblogs.com/candlia/p/11920342.html

spark-sql架构与原理

一. 整体架构

1.2 SQLContext

1.2.1 Catalog

1.2.2 SparkSQLParser

1.2.3 Analyzer

1.2.4 Optimizer

1.2.5 SparkPlanner

1.2.6 PrepareForExecution

1.3 QueryExecution

1.4 LogicalPlan and SparkPlan

二. Catalyst

三. SparkSQL整体架构（前端+后端）