Backport #92419 to 25.10: Inherit source part serialization info settings during mutation in MergeTree

robot-clickhouse · robot-clickhouse · commit 391d70099fbb · 2025-12-19T14:13:34.000Z
diff --git a/src/Storages/MergeTree/MutateTask.cpp b/src/Storages/MergeTree/MutateTask.cpp
@@ -521,13 +521,25 @@ getColumnsForNewDataPart(
         }
     }
 
-    SerializationInfo::Settings settings
+    SerializationInfo::Settings settings;
+    /// If mutations doesn't affect all columns we must use serialization info settings from source part,
+    /// because data files of some columns might be copied without actual serialization, so changes in serialization
+    /// settings will not be applied for them (for example, new serialization versions for data types).
+    if (!affects_all_columns)
     {
-        (*source_part->storage.getSettings())[MergeTreeSetting::ratio_of_defaults_for_sparse_serialization],
-        false,
-        (*source_part->storage.getSettings())[MergeTreeSetting::serialization_info_version],
-        (*source_part->storage.getSettings())[MergeTreeSetting::string_serialization_version],
-    };
+        settings = serialization_infos.getSettings();
+    }
+    /// Otherwise use fresh settings from storage.
+    else
+    {
+        settings = SerializationInfo::Settings
+        {
+            (*source_part->storage.getSettings())[MergeTreeSetting::ratio_of_defaults_for_sparse_serialization],
+            false,
+            (*source_part->storage.getSettings())[MergeTreeSetting::serialization_info_version],
+            (*source_part->storage.getSettings())[MergeTreeSetting::string_serialization_version],
+        };
+    }
 
     SerializationInfoByName new_serialization_infos(settings);
     for (const auto & [name, old_info] : serialization_infos)
diff --git a/tests/queries/0_stateless/03762_mutation_of_columns_in_wide_part_with_new_type_serialization_version.reference b/tests/queries/0_stateless/03762_mutation_of_columns_in_wide_part_with_new_type_serialization_version.reference
@@ -0,0 +1 @@
+abc99	def
diff --git a/tests/queries/0_stateless/03762_mutation_of_columns_in_wide_part_with_new_type_serialization_version.sql b/tests/queries/0_stateless/03762_mutation_of_columns_in_wide_part_with_new_type_serialization_version.sql
@@ -0,0 +1,11 @@
+drop table if exists test;
+create table test (s String) engine=MergeTree order by tuple() settings min_bytes_for_wide_part=1, string_serialization_version='single_stream';
+insert into test select 'abc' || toString(number) from numbers(100);
+alter table test modify setting string_serialization_version='with_size_stream';
+alter table test add column s1 String default 'def' settings alter_sync=2;
+alter table test materialize column s1 settings mutations_sync=1;
+detach table test;
+attach table test;
+select max(s), max(s1) from test;
+drop table test;
+
