[SPARK-18086] Add support for Hive session vars.

## What changes were proposed in this pull request?

This adds support for Hive variables:

* Makes values set via `spark-sql --hivevar name=value` accessible
* Adds `getHiveVar` and `setHiveVar` to the `HiveClient` interface
* Adds a SessionVariables trait for sessions like Hive that support variables (including Hive vars)
* Adds SessionVariables support to variable substitution
* Adds SessionVariables support to the SET command

## How was this patch tested?

* Adds a test to all supported Hive versions for accessing Hive variables
* Adds HiveVariableSubstitutionSuite

Author: Ryan Blue <blue@apache.org>

Closes #15738 from rdblue/SPARK-18086-add-hivevar-support.

1 files changed, 5 insertions, 1 deletions

diff --git a/sql/hive-thriftserver/src/main/scala/org/apache/spark/sql/hive/thriftserver/SparkSQLCLIDriver.scala b/sql/hive-thriftserver/src/main/scala/org/apache/spark/sql/hive/thriftserver/SparkSQLCLIDriver.scala
index 5dafec1c30..0c79b6f421 100644
--- a/sql/hive-thriftserver/src/main/scala/org/apache/spark/sql/hive/thriftserver/SparkSQLCLIDriver.scala
+++ b/sql/hive-thriftserver/src/main/scala/org/apache/spark/sql/hive/thriftserver/SparkSQLCLIDriver.scala
@@ -38,7 +38,7 @@ import org.apache.thrift.transport.TSocket
 
 import org.apache.spark.internal.Logging
 import org.apache.spark.sql.AnalysisException
-import org.apache.spark.sql.hive.HiveUtils
+import org.apache.spark.sql.hive.{HiveSessionState, HiveUtils}
 import org.apache.spark.util.ShutdownHookManager
 
 /**
@@ -291,6 +291,10 @@ private[hive] class SparkSQLCLIDriver extends CliDriver with Logging {
     throw new RuntimeException("Remote operations not supported")
   }
 
+  override def setHiveVariables(hiveVariables: java.util.Map[String, String]): Unit = {
+    hiveVariables.asScala.foreach(kv => SparkSQLEnv.sqlContext.conf.setConfString(kv._1, kv._2))
+  }
+
   override def processCmd(cmd: String): Int = {
     val cmd_trimmed: String = cmd.trim()
     val cmd_lower = cmd_trimmed.toLowerCase(Locale.ENGLISH)