[GitHub] [spark] LantaoJin commented on a change in pull request #28938: [SPARK-32118][SQL] Use fine-grained read write lock for each database in HiveExternalCatalog

[GitBox <gi...@apache.org>]

LantaoJin commented on a change in pull request #28938:
URL: https://github.com/apache/spark/pull/28938#discussion_r508276917



##########
File path: sql/hive/src/main/scala/org/apache/spark/sql/hive/client/HiveClientImpl.scala
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@@ -103,22 +103,24 @@ private[hive] class HiveClientImpl(
   // Circular buffer to hold what hive prints to STDOUT and ERR.  Only printed when failures occur.
   private val outputBuffer = new CircularBuffer()
 
-  private val shim = version match {
-    case hive.v12 => new Shim_v0_12()
-    case hive.v13 => new Shim_v0_13()
-    case hive.v14 => new Shim_v0_14()
-    case hive.v1_0 => new Shim_v1_0()
-    case hive.v1_1 => new Shim_v1_1()
-    case hive.v1_2 => new Shim_v1_2()
-    case hive.v2_0 => new Shim_v2_0()
-    case hive.v2_1 => new Shim_v2_1()
-    case hive.v2_2 => new Shim_v2_2()
-    case hive.v2_3 => new Shim_v2_3()
-    case hive.v3_0 => new Shim_v3_0()
-    case hive.v3_1 => new Shim_v3_1()
-  }
-
-  // Create an internal session state for this HiveClientImpl.
+  private val shim: ThreadLocal[Shim] = new ThreadLocal[Shim]() {
+    override def initialValue(): Shim = version match {
+      case hive.v12 => new Shim_v0_12()
+      case hive.v13 => new Shim_v0_13()
+      case hive.v14 => new Shim_v0_14()
+      case hive.v1_0 => new Shim_v1_0()
+      case hive.v1_1 => new Shim_v1_1()
+      case hive.v1_2 => new Shim_v1_2()
+      case hive.v2_0 => new Shim_v2_0()
+      case hive.v2_1 => new Shim_v2_1()
+      case hive.v2_2 => new Shim_v2_2()
+      case hive.v2_3 => new Shim_v2_3()
+      case hive.v3_0 => new Shim_v3_0()
+      case hive.v3_1 => new Shim_v3_1()
+    }
+  }
+
+  // Since HiveClientImpl is thread local, one state per HiveClientImpl

Review comment:
       Oh, this comment should be reverted.




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