From cdf2c9d7a30ca8102c3d4ee4e3e633b3b5024b4d Mon Sep 17 00:00:00 2001
From: JaySon <tshent@qq.com>
Date: Mon, 23 Mar 2020 07:47:01 -0500
Subject: [PATCH] [FLASH-1026] Synchronization between drop table and remove
 region (#538)

---
 dbms/src/Interpreters/InterpreterDropQuery.cpp   |  4 ++--
 dbms/src/Storages/DeltaMerge/DeltaMergeStore.cpp | 13 ++++++++-----
 2 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/dbms/src/Interpreters/InterpreterDropQuery.cpp b/dbms/src/Interpreters/InterpreterDropQuery.cpp
index 0a9c8f1cd60..98e6443dbee 100644
--- a/dbms/src/Interpreters/InterpreterDropQuery.cpp
+++ b/dbms/src/Interpreters/InterpreterDropQuery.cpp
@@ -123,11 +123,11 @@ BlockIO InterpreterDropQuery::execute()
                     ErrorCodes::TABLE_WAS_NOT_DROPPED);
         }
 
-        table.first->shutdown();
-
         /// If table was already dropped by anyone, an exception will be thrown
         auto table_lock = table.first->lockForAlter(__PRETTY_FUNCTION__);
 
+        table.first->shutdown();
+
         String current_table_name = table.first->getTableName();
 
         if (drop.detach)
diff --git a/dbms/src/Storages/DeltaMerge/DeltaMergeStore.cpp b/dbms/src/Storages/DeltaMerge/DeltaMergeStore.cpp
index c26ec91ea12..8d4cdc41330 100644
--- a/dbms/src/Storages/DeltaMerge/DeltaMergeStore.cpp
+++ b/dbms/src/Storages/DeltaMerge/DeltaMergeStore.cpp
@@ -216,13 +216,15 @@ void DeltaMergeStore::shutdown()
 {
     bool v = false;
     if (!shutdown_called.compare_exchange_strong(v, true))
-        return ;
+        return;
 
+    LOG_DEBUG(log, "Shutdown DeltaMerge Store start [" << db_name << "." << table_name << "]");
     background_pool.removeTask(gc_handle);
     gc_handle = nullptr;
 
     background_pool.removeTask(background_task_handle);
     background_task_handle = nullptr;
+    LOG_DEBUG(log, "Shutdown DeltaMerge Store start [" << db_name << "." << table_name << "]");
 }
 
 DMContextPtr DeltaMergeStore::newDMContext(const Context & db_context, const DB::Settings & db_settings)
@@ -811,6 +813,9 @@ void DeltaMergeStore::checkSegmentUpdate(const DMContextPtr & dm_context, const
     auto try_add_background_task = [&](const BackgroundTask & task) {
         if (background_tasks.length() <= std::max(id_to_segment.size() * 2, background_pool.getNumberOfThreads() * 5))
         {
+            if (shutdown_called.load(std::memory_order_relaxed))
+                return;
+
             // Prevent too many tasks.
             background_tasks.addTask(task, thread_type, log);
             background_task_handle->wake();
@@ -997,15 +1002,13 @@ bool DeltaMergeStore::handleBackgroundTask()
             left = segmentMergeDelta(*task.dm_context, task.segment, false);
             type = ThreadType::BG_MergeDelta;
             break;
-        case Compact:
-        {
+        case Compact: {
             task.segment->getDelta()->compact(*task.dm_context);
             left = task.segment;
             type = ThreadType::BG_Compact;
             break;
         }
-        case Flush:
-        {
+        case Flush: {
             task.segment->getDelta()->flush(*task.dm_context);
             left = task.segment;
             type = ThreadType::BG_Flush;