Merge pull request #12618 from ClickHouse/fix-external-sort-pipeline-stuck

Fix external sort pipeline stuck

src/Processors/Transforms/MergeSortingTransform.cpp

@@ -231,9 +231,8 @@ void MergeSortingTransform::generate()
             ProfileEvents::increment(ProfileEvents::ExternalSortMerge);
             LOG_INFO(log, "There are {} temporary sorted parts to merge.", temporary_files.size());
 
-            if (!chunks.empty())
-                processors.emplace_back(std::make_shared<MergeSorterSource>(
-                        header_without_constants, std::move(chunks), description, max_merged_block_size, limit));
+            processors.emplace_back(std::make_shared<MergeSorterSource>(
+                    header_without_constants, std::move(chunks), description, max_merged_block_size, limit));
         }
 
         generated_prefix = true;

tests/queries/0_stateless/00110_external_sort.reference

@@ -8,3 +8,14 @@
 8140551
 5427034
 2713517
+-
+440516
+1540521
+733765
+1833770
+1027014
+220258
+1320263
+513507
+1613512
+806756

tests/queries/0_stateless/00110_external_sort.sql

 SET max_memory_usage = 300000000;
 SET max_bytes_before_external_sort = 20000000;
 SELECT number FROM (SELECT number FROM system.numbers LIMIT 10000000) ORDER BY number * 1234567890123456789 LIMIT 9999990, 10;
+
+SELECT '-';
+
+SET max_bytes_before_external_sort = 33554432;
+set max_block_size = 1048576;
+SELECT number FROM (SELECT number FROM numbers(2097152)) ORDER BY number * 1234567890123456789 LIMIT 2097142, 10;