[SPARK-14720][SPARK-13643] Move Hive-specific methods into HiveSessionState and Create a SparkSession class

## What changes were proposed in this pull request?
This PR has two main changes.
1. Move Hive-specific methods from HiveContext to HiveSessionState, which help the work of removing HiveContext.
2. Create a SparkSession Class, which will later be the entry point of Spark SQL users.

## How was this patch tested?
Existing tests

This PR is trying to fix test failures of https://github.com/apache/spark/pull/12485.

Author: Andrew Or <andrew@databricks.com>
Author: Yin Huai <yhuai@databricks.com>

Closes #12522 from yhuai/spark-session.

1 files changed, 7 insertions, 0 deletions

diff --git a/core/src/main/scala/org/apache/spark/internal/config/package.scala b/core/src/main/scala/org/apache/spark/internal/config/package.scala
index 94b50ee065..2c1e0b71e3 100644
--- a/core/src/main/scala/org/apache/spark/internal/config/package.scala
+++ b/core/src/main/scala/org/apache/spark/internal/config/package.scala
@@ -89,4 +89,11 @@ package object config {
     .stringConf
     .toSequence
     .createWithDefault(Nil)
+
+  // Note: This is a SQL config but needs to be in core because the REPL depends on it
+  private[spark] val CATALOG_IMPLEMENTATION = ConfigBuilder("spark.sql.catalogImplementation")
+    .internal()
+    .stringConf
+    .checkValues(Set("hive", "in-memory"))
+    .createWithDefault("in-memory")
 }