[GitHub] spark pull request: [SPARK-4103][SQL] Clean up SessionState in Hiv...

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

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

    https://github.com/apache/spark/pull/2967#discussion_r19445035
  
    --- Diff: sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveContext.scala ---
    @@ -230,13 +230,21 @@ class HiveContext(sc: SparkContext) extends SQLContext(sc) {
        * in the HiveConf.
        */
       @transient lazy val hiveconf = new HiveConf(classOf[SessionState])
    -  @transient protected[hive] lazy val sessionState = {
    -    val ss = new SessionState(hiveconf)
    -    setConf(hiveconf.getAllProperties)  // Have SQLConf pick up the initial set of HiveConf.
    -    SessionState.start(ss)
    -    ss.err = new PrintStream(outputBuffer, true, "UTF-8")
    -    ss.out = new PrintStream(outputBuffer, true, "UTF-8")
     
    +  /**
    +   * If the thread local sessionstate is not set, start a new SessionState
    +   * SessionState.start will put ss to thread local
    +   * @return
    +   */
    +  def getSessionState() = {
    +    var ss = SessionState.get
    +    if (ss == null) {
    +      ss = new SessionState(hiveconf)
    +      setConf(hiveconf.getAllProperties) // Have SQLConf pick up the initial set of HiveConf.
    +      SessionState.start(ss)
    +      ss.err = new PrintStream(outputBuffer, true, "UTF-8")
    +      ss.out = new PrintStream(outputBuffer, true, "UTF-8")
    +    }
    --- End diff --
    
    If we use lazy eval, we have to relies on SessionState.start(sessionState) to initialize it. It may be invoked multiple times in various locations. Here we relies on checking ThreadLocal variable and initialize it at the first call to avoid this.


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