[SPARK-16904][SQL] Removal of Hive Built-in Hash Functions and TestHiveFunctionRegistry

### What changes were proposed in this pull request?

Currently, the Hive built-in `hash` function is not being used in Spark since Spark 2.0. The public interface does not allow users to unregister the Spark built-in functions. Thus, users will never use Hive's built-in `hash` function.

The only exception here is `TestHiveFunctionRegistry`, which allows users to unregister the built-in functions. Thus, we can load Hive's hash function in the test cases. If we disable it, 10+ test cases will fail because the results are different from the Hive golden answer files.

This PR is to remove `hash` from the list of `hiveFunctions` in `HiveSessionCatalog`. It will also remove `TestHiveFunctionRegistry`. This removal makes us easier to remove `TestHiveSessionState` in the future.
### How was this patch tested?
N/A

Author: gatorsmile <gatorsmile@gmail.com>

Closes #14498 from gatorsmile/removeHash.

sql/hive/compatibility/src/test/scala/org/apache/spark/sql/hive/execution/HiveCompatibilitySuite.scala

@@ -57,8 +57,6 @@ class HiveCompatibilitySuite extends HiveQueryFileTest with BeforeAndAfter {
     TestHive.setConf(SQLConf.COLUMN_BATCH_SIZE, 5)
     // Enable in-memory partition pruning for testing purposes
     TestHive.setConf(SQLConf.IN_MEMORY_PARTITION_PRUNING, true)
-    // Use Hive hash expression instead of the native one
-    TestHive.sessionState.functionRegistry.unregisterFunction("hash")
     // Ensures that the plans generation use metastore relation and not OrcRelation
     // Was done because SqlBuilder does not work with plans having logical relation
     TestHive.setConf(HiveUtils.CONVERT_METASTORE_ORC, false)
@@ -76,7 +74,6 @@ class HiveCompatibilitySuite extends HiveQueryFileTest with BeforeAndAfter {
       TestHive.setConf(SQLConf.IN_MEMORY_PARTITION_PRUNING, originalInMemoryPartitionPruning)
       TestHive.setConf(HiveUtils.CONVERT_METASTORE_ORC, originalConvertMetastoreOrc)
       TestHive.setConf(SQLConf.CROSS_JOINS_ENABLED, originalCrossJoinEnabled)
-      TestHive.sessionState.functionRegistry.restore()
 
       // For debugging dump some statistics about how much time was spent in various optimizer rules
       logWarning(RuleExecutor.dumpTimeSpent())
@@ -581,7 +578,26 @@ class HiveCompatibilitySuite extends HiveQueryFileTest with BeforeAndAfter {
     "auto_join6",
     "auto_join7",
     "auto_join8",
-    "auto_join9"
+    "auto_join9",
+
+    // These tests are based on the Hive's hash function, which is different from Spark
+    "auto_join19",
+    "auto_join22",
+    "auto_join25",
+    "auto_join26",
+    "auto_join27",
+    "auto_join28",
+    "auto_join30",
+    "auto_join31",
+    "auto_join_nulls",
+    "auto_join_reordering_values",
+    "correlationoptimizer1",
+    "correlationoptimizer2",
+    "correlationoptimizer3",
+    "correlationoptimizer4",
+    "multiMapJoin1",
+    "orc_dictionary_threshold",
+    "udf_hash"
   )
 
   /**
@@ -601,16 +617,6 @@ class HiveCompatibilitySuite extends HiveQueryFileTest with BeforeAndAfter {
     "annotate_stats_part",
     "annotate_stats_table",
     "annotate_stats_union",
-    "auto_join19",
-    "auto_join22",
-    "auto_join25",
-    "auto_join26",
-    "auto_join27",
-    "auto_join28",
-    "auto_join30",
-    "auto_join31",
-    "auto_join_nulls",
-    "auto_join_reordering_values",
     "binary_constant",
     "binarysortable_1",
     "cast1",
@@ -623,15 +629,11 @@ class HiveCompatibilitySuite extends HiveQueryFileTest with BeforeAndAfter {
     "compute_stats_long",
     "compute_stats_string",
     "convert_enum_to_string",
-    "correlationoptimizer1",
     "correlationoptimizer10",
     "correlationoptimizer11",
     "correlationoptimizer13",
     "correlationoptimizer14",
     "correlationoptimizer15",
-    "correlationoptimizer2",
-    "correlationoptimizer3",
-    "correlationoptimizer4",
     "correlationoptimizer6",
     "correlationoptimizer7",
     "correlationoptimizer8",
@@ -871,7 +873,6 @@ class HiveCompatibilitySuite extends HiveQueryFileTest with BeforeAndAfter {
     "merge2",
     "merge4",
     "mergejoins",
-    "multiMapJoin1",
     "multiMapJoin2",
     "multi_insert_gby",
     "multi_insert_gby3",
@@ -893,7 +894,6 @@ class HiveCompatibilitySuite extends HiveQueryFileTest with BeforeAndAfter {
     "nullinput2",
     "nullscript",
     "optional_outer",
-    "orc_dictionary_threshold",
     "order",
     "order2",
     "outer_join_ppr",
@@ -1026,7 +1026,6 @@ class HiveCompatibilitySuite extends HiveQueryFileTest with BeforeAndAfter {
     "udf_from_unixtime",
     "udf_greaterthan",
     "udf_greaterthanorequal",
-    "udf_hash",
     "udf_hex",
     "udf_if",
     "udf_index",

sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveSessionCatalog.scala

@@ -233,7 +233,6 @@ private[sql] class HiveSessionCatalog(
   // in_file, index, matchpath, ngrams, noop, noopstreaming, noopwithmap,
   // noopwithmapstreaming, parse_url_tuple, reflect2, windowingtablefunction.
   private val hiveFunctions = Seq(
-    "hash",
     "histogram_numeric",
     "percentile"
   )

sql/hive/src/main/scala/org/apache/spark/sql/hive/test/TestHive.scala

@@ -492,24 +492,6 @@ private[hive] class TestHiveQueryExecution(
   }
 }
 
-
-private[hive] class TestHiveFunctionRegistry extends SimpleFunctionRegistry {
-
-  private val removedFunctions =
-    collection.mutable.ArrayBuffer.empty[(String, (ExpressionInfo, FunctionBuilder))]
-
-  def unregisterFunction(name: String): Unit = synchronized {
-    functionBuilders.remove(name).foreach(f => removedFunctions += name -> f)
-  }
-
-  def restore(): Unit = synchronized {
-    removedFunctions.foreach {
-      case (name, (info, builder)) => registerFunction(name, info, builder)
-    }
-  }
-}
-
-
 private[hive] class TestHiveSessionState(
     sparkSession: TestHiveSparkSession)
   extends HiveSessionState(sparkSession) { self =>
@@ -525,16 +507,6 @@ private[hive] class TestHiveSessionState(
     }
   }
 
-  override lazy val functionRegistry: TestHiveFunctionRegistry = {
-    // We use TestHiveFunctionRegistry at here to track functions that have been explicitly
-    // unregistered (through TestHiveFunctionRegistry.unregisterFunction method).
-    val fr = new TestHiveFunctionRegistry
-    org.apache.spark.sql.catalyst.analysis.FunctionRegistry.expressions.foreach {
-      case (name, (info, builder)) => fr.registerFunction(name, info, builder)
-    }
-    fr
-  }
-
   override def executePlan(plan: LogicalPlan): TestHiveQueryExecution = {
     new TestHiveQueryExecution(sparkSession, plan)
   }