fix

src/Storages/MergeTree/DataPartsExchange.cpp

@@ -582,6 +582,8 @@ MergeTreeData::MutableDataPartPtr Fetcher::fetchPart(
                 tryLogCurrentException(log);
             }
 
+            temporary_directory_lock = {};
+
             /// Try again but without zero-copy
             return fetchPart(metadata_snapshot, context, part_name, replica_path, host, port, timeouts,
                 user, password, interserver_scheme, throttler, to_detached, tmp_prefix, nullptr, false, disk);

src/Storages/MergeTree/MergeTask.cpp

@@ -142,6 +142,7 @@ bool MergeTask::ExecuteAndFinalizeHorizontalPart::prepare()
     if (global_ctx->data_part_storage_builder->exists())
         throw Exception("Directory " + global_ctx->data_part_storage_builder->getFullPath() + " already exists", ErrorCodes::DIRECTORY_ALREADY_EXISTS);
 
+    if (!global_ctx->parent_part)
         global_ctx->temporary_directory_lock = global_ctx->data->getTemporaryPartDirectoryHolder(local_tmp_part_basename);
 
     global_ctx->all_column_names = global_ctx->metadata_snapshot->getColumns().getNamesOfPhysical();

src/Storages/MergeTree/MergeTreeData.cpp

@@ -2864,6 +2864,13 @@ void MergeTreeData::preparePartForCommit(MutableDataPartPtr & part, Transaction
     part->is_temp = false;
     part->setState(DataPartState::PreActive);
 
+    assert([&]()
+           {
+               String dir_name = fs::path(part->data_part_storage->getRelativePath()).filename();
+               bool may_be_cleaned_up = dir_name.starts_with("tmp_") || dir_name.starts_with("tmp-fetch_");
+               return !may_be_cleaned_up || temporary_parts.contains(dir_name);
+           }());
+
     part->renameTo(part->name, true, builder);
 
     data_parts_indexes.insert(part);

src/Storages/MergeTree/TemporaryParts.cpp

@@ -15,10 +15,10 @@ bool TemporaryParts::contains(const std::string & basename) const
     return parts.contains(basename);
 }
 
-void TemporaryParts::add(std::string basename)
+void TemporaryParts::add(const std::string & basename)
 {
     std::lock_guard lock(mutex);
-    bool inserted = parts.emplace(std::move(basename)).second;
+    bool inserted = parts.emplace(basename).second;
     if (!inserted)
         throw Exception(ErrorCodes::LOGICAL_ERROR, "Temporary part {} already added", basename);
 }

src/Storages/MergeTree/TemporaryParts.h

@@ -18,6 +18,10 @@ private:
     /// NOTE: It is pretty short, so use STL is fine.
     std::unordered_set<std::string> parts;
 
+    void add(const std::string & basename);
+    void remove(const std::string & basename);
+
+    friend class MergeTreeData;
 public:
     /// Returns true if passed part name is active.
     /// (is the destination for one of active mutation/merge).
@@ -25,9 +29,6 @@ public:
     /// NOTE: that it accept basename (i.e. dirname), not the path,
     /// since later requires canonical form.
     bool contains(const std::string & basename) const;
-
-    void add(std::string basename);
-    void remove(const std::string & basename);
 };
 
 }

tests/config/config.d/merge_tree_settings.xml

@@ -2,7 +2,7 @@
     <merge_tree>
         <!-- 10 seconds (default is 1 minute) -->
         <zookeeper_session_expiration_check_period>10</zookeeper_session_expiration_check_period>
-        <!-- Default is 86400 (1 day), but we have protection from removal of tmp dirs in use -->
-        <temporary_directories_lifetime>0</temporary_directories_lifetime>
+        <!-- Default is 86400 (1 day), but we have protection from removal of tmp dirs that are currently in use -->
+        <temporary_directories_lifetime>1</temporary_directories_lifetime>
     </merge_tree>
 </clickhouse>

tests/queries/0_stateless/02401_merge_tree_old_tmp_dirs_cleanup.reference

@@ -0,0 +1 @@
+10	45

tests/queries/0_stateless/02401_merge_tree_old_tmp_dirs_cleanup.sql

@@ -0,0 +1,11 @@
+DROP TABLE IF EXISTS test_inserts;
+
+CREATE TABLE test_inserts (`key` Int, `part` Int) ENGINE = MergeTree PARTITION BY part ORDER BY key
+SETTINGS temporary_directories_lifetime = 0, merge_tree_clear_old_temporary_directories_interval_seconds = 0;
+
+INSERT INTO test_inserts SELECT sleep(1), number FROM numbers(10)
+SETTINGS max_insert_delayed_streams_for_parallel_write = 100, max_insert_block_size = 1, min_insert_block_size_rows = 1;
+
+SELECT count(), sum(part) FROM test_inserts;
+
+DROP TABLE test_inserts;