Investigating [#METR-21326].

dbms/include/DB/Storages/MergeTree/MergeTreeDataMerger.h

@@ -21,8 +21,6 @@ public:
 	using AllowedMergingPredicate = std::function<bool (const MergeTreeData::DataPartPtr &, const MergeTreeData::DataPartPtr &)>;
 
 public:
-	static const size_t NO_LIMIT = std::numeric_limits<size_t>::max();
-
 	MergeTreeDataMerger(MergeTreeData & data_);
 
 	void setCancellationHook(CancellationHook cancellation_hook_);

dbms/src/Storages/StorageReplicatedMergeTree.cpp

@@ -1647,6 +1647,7 @@ bool StorageReplicatedMergeTree::canMergeParts(
 void StorageReplicatedMergeTree::mergeSelectingThread()
 {
 	setThreadName("ReplMTMergeSel");
+	LOG_DEBUG(log, "Merge selecting thread started");
 
 	bool need_pull = true;