Github user kunalkhamar commented on a diff in the pull request:
https://github.com/apache/spark/pull/17433#discussion_r108265096
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/internal/SessionState.scala ---
@@ -179,88 +132,295 @@ private[sql] class SessionState(
}
}
-
private[sql] object SessionState {
+ /**
+ * Create a new [[SessionState]] for the given session.
+ */
+ def apply(session: SparkSession): SessionState = {
+ new SessionStateBuilder(session).build()
+ }
+
+ def newHadoopConf(hadoopConf: Configuration, sqlConf: SQLConf):
Configuration = {
+ val newHadoopConf = new Configuration(hadoopConf)
+ sqlConf.getAllConfs.foreach { case (k, v) => if (v ne null)
newHadoopConf.set(k, v) }
+ newHadoopConf
+ }
+}
+
+/**
+ * Builder class that coordinates construction of a new [[SessionState]].
+ *
+ * The builder explicitly defines all components needed by the session
state, and creates a session
+ * state when `build` is called. Components should only be initialized
once. This is not a problem
+ * for most components as they are only used in the `build` function.
However some components
+ * (`conf`, `catalog`, `functionRegistry`, `experimentalMethods` &
`sqlParser`) are as dependencies
+ * for other components and are shared as a result. These components are
defined as lazy vals to
+ * make sure the component is created only once.
+ *
+ * A developer can modify the builder by providing custom versions of
components, or by using the
+ * hooks provided for the analyzer, optimizer & planner. There are some
dependencies between the
+ * components (they are documented per dependency), a developer should
respect these when making
+ * modifications in order to prevent initialization problems.
+ *
+ * A parent [[SessionState]] can be used to initialize the new
[[SessionState]]. The new session
+ * state will clone the parent sessions state's `conf`,
`functionRegistry`, `experimentalMethods`
+ * and `catalog` fields. Note that the state is cloned when `build` is
called, and not before.
+ */
+@Experimental
+@InterfaceStability.Unstable
+abstract class BaseSessionStateBuilder(
+ val session: SparkSession,
+ val parentState: Option[SessionState] = None) {
+ type NewBuilder = (SparkSession, Option[SessionState]) =>
BaseSessionStateBuilder
- def apply(sparkSession: SparkSession): SessionState = {
- apply(sparkSession, new SQLConf)
+ /**
+ * Extract entries from `SparkConf` and put them in the `SQLConf`
+ */
+ protected def mergeSparkConf(sqlConf: SQLConf, sparkConf: SparkConf):
Unit = {
+ sparkConf.getAll.foreach { case (k, v) =>
+ sqlConf.setConfString(k, v)
+ }
}
- def apply(sparkSession: SparkSession, sqlConf: SQLConf): SessionState = {
- val sparkContext = sparkSession.sparkContext
+ /**
+ * SQL-specific key-value configurations.
+ *
+ * These either get cloned from a pre-existing instance or newly
created. The conf is always
+ * merged with its [[SparkConf]].
+ */
+ protected lazy val conf: SQLConf = {
+ val conf = parentState.map(_.conf.clone()).getOrElse(new SQLConf)
+ mergeSparkConf(conf, session.sparkContext.conf)
+ conf
+ }
- // Automatically extract all entries and put them in our SQLConf
- mergeSparkConf(sqlConf, sparkContext.getConf)
+ /**
+ * Internal catalog managing functions registered by the user.
+ *
+ * This either gets cloned from a pre-existing version or cloned from
the build-in registry.
--- End diff --
super nit: built-in registry
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