From d6d0404c48af9cf56441a8def682e9fc47b3349b Mon Sep 17 00:00:00 2001
From: Vitaliy Zakaznikov <vzakaznikov@protonmail.com>
Date: Fri, 14 Jun 2019 16:27:43 -0400
Subject: [PATCH] * Fixing bug in StorageLiveView.cpp getHeader() method   that
 sometimes addressed invalid pointer when getHeader()   method was called
 without holding the mutex

---
 dbms/src/Storages/StorageLiveView.cpp | 28 +++++++++++----------------
 1 file changed, 11 insertions(+), 17 deletions(-)

diff --git a/dbms/src/Storages/StorageLiveView.cpp b/dbms/src/Storages/StorageLiveView.cpp
index 917d62baaa4..eecc7f6d1dc 100644
--- a/dbms/src/Storages/StorageLiveView.cpp
+++ b/dbms/src/Storages/StorageLiveView.cpp
@@ -159,24 +159,18 @@ Block StorageLiveView::getHeader() const
 {
     if (!sample_block)
     {
-        if (!(*blocks_ptr) || (*blocks_ptr)->empty())
+        auto storage = global_context.getTable(select_database_name, select_table_name);
+        sample_block = InterpreterSelectQuery(inner_query, global_context, storage,
+            SelectQueryOptions(QueryProcessingStage::Complete)).getSampleBlock();
+        sample_block.insert({DataTypeUInt64().createColumnConst(
+            sample_block.rows(), 0)->convertToFullColumnIfConst(),
+            std::make_shared<DataTypeUInt64>(),
+            "_version"});
+        /// convert all columns to full columns
+        /// in case some of them are constant
+        for (size_t i = 0; i < sample_block.columns(); ++i)
         {
-            auto storage = global_context.getTable(select_database_name, select_table_name);
-            sample_block = InterpreterSelectQuery(inner_query, global_context, storage, SelectQueryOptions(QueryProcessingStage::Complete)).getSampleBlock();
-            sample_block.insert({DataTypeUInt64().createColumnConst(
-                sample_block.rows(), 0)->convertToFullColumnIfConst(),
-                std::make_shared<DataTypeUInt64>(),
-                "_version"});
-            /// convert all columns to full columns
-            /// in case some of them are constant
-            for (size_t i = 0; i < sample_block.columns(); ++i)
-            {
-                sample_block.safeGetByPosition(i).column = sample_block.safeGetByPosition(i).column->convertToFullColumnIfConst();
-            }
-        }
-        else
-        {
-            sample_block = (*blocks_ptr)->front().cloneEmpty();
+            sample_block.safeGetByPosition(i).column = sample_block.safeGetByPosition(i).column->convertToFullColumnIfConst();
         }
     }