[HOTFIX][SQL] Fix broken cached test

Added in #5475. Pointed as broken in #5639.
/cc marmbrus

Author: Liang-Chi Hsieh <viirya@gmail.com>

Closes #5640 from viirya/fix_cached_test and squashes the following commits:

c0cf69a [Liang-Chi Hsieh] Fix broken cached test.

1 files changed, 14 insertions, 7 deletions

diff --git a/sql/core/src/test/scala/org/apache/spark/sql/CachedTableSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/CachedTableSuite.scala
index 01e3b86710..0772e5e187 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/CachedTableSuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/CachedTableSuite.scala
@@ -300,19 +300,26 @@ class CachedTableSuite extends QueryTest {
   }
 
   test("Clear accumulators when uncacheTable to prevent memory leaking") {
-    val accsSize = Accumulators.originals.size
-
     sql("SELECT key FROM testData LIMIT 10").registerTempTable("t1")
     sql("SELECT key FROM testData LIMIT 5").registerTempTable("t2")
-    cacheTable("t1")
-    cacheTable("t2")
+
+    Accumulators.synchronized {
+      val accsSize = Accumulators.originals.size
+      cacheTable("t1")
+      cacheTable("t2")
+      assert((accsSize + 2) == Accumulators.originals.size)
+    }
+
     sql("SELECT * FROM t1").count()
     sql("SELECT * FROM t2").count()
     sql("SELECT * FROM t1").count()
     sql("SELECT * FROM t2").count()
-    uncacheTable("t1")
-    uncacheTable("t2")
 
-    assert(accsSize >= Accumulators.originals.size)
+    Accumulators.synchronized {
+      val accsSize = Accumulators.originals.size
+      uncacheTable("t1")
+      uncacheTable("t2")
+      assert((accsSize - 2) == Accumulators.originals.size)
+    }
   }
 }