Github user dilipbiswal commented on a diff in the pull request: https://github.com/apache/spark/pull/13200#discussion_r63992730 --- Diff: sql/core/src/main/scala/org/apache/spark/sql/SparkSession.scala --- @@ -735,29 +731,130 @@ object SparkSession { } /** - * Gets an existing [[SparkSession]] or, if there is no existing one, creates a new one - * based on the options set in this builder. + * Gets an existing [[SparkSession]] or, if there is no existing one, creates a new + * one based on the options set in this builder. + * + * This method first checks whether there is a valid thread-local SparkSession, + * and if yes, return that one. It then checks whether there is a valid global + * default SparkSession, and if yes, return that one. If no valid global default + * SparkSession exists, the method creates a new SparkSession and assigns the + * newly created SparkSession as the global default. + * + * In case an existing SparkSession is returned, the config options specified in + * this builder will be applied to the existing SparkSession. * * @since 2.0.0 */ def getOrCreate(): SparkSession = synchronized { - // Step 1. Create a SparkConf - // Step 2. Get a SparkContext - // Step 3. Get a SparkSession - val sparkConf = new SparkConf() - options.foreach { case (k, v) => sparkConf.set(k, v) } - val sparkContext = SparkContext.getOrCreate(sparkConf) - - SQLContext.getOrCreate(sparkContext).sparkSession + // Get the session from current thread's active session. + var session = activeThreadSession.get() + if ((session ne null) && !session.sparkContext.isStopped) { + options.foreach { case (k, v) => session.conf.set(k, v) } + return session + } + + // Global synchronization so we will only set the default session once. + SparkSession.synchronized { + // If the current thread does not have an active session, get it from the global session. + session = defaultSession.get() + if ((session ne null) && !session.sparkContext.isStopped) { + options.foreach { case (k, v) => session.conf.set(k, v) } + return session + } + + // No active nor global default session. Create a new one. + val sparkContext = userSuppliedContext.getOrElse { + // set app name if not given + if (!options.contains("spark.app.name")) { + options += "spark.app.name" -> java.util.UUID.randomUUID().toString + } + + val sparkConf = new SparkConf() + options.foreach { case (k, v) => sparkConf.set(k, v) } + SparkContext.getOrCreate(sparkConf) + } + session = new SparkSession(sparkContext) + options.foreach { case (k, v) => session.conf.set(k, v) } + defaultSession.set(session) --- End diff -- @rxin Hi Reynold, i had a minor question just for my understanding. When users do a new SQLContext() , we create a implicit SparkSession. Should this session be made the defaultSession ? If we call, 1) new SQLContext 2) builder.getOrCreate() then whats the expected behaviour ?
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