Merge pull request #21303 from ucasFL/forbid

Forbid to drop a column if it's referenced by materialized view

src/Interpreters/InterpreterAlterQuery.cpp

@@ -137,7 +137,7 @@ BlockIO InterpreterAlterQuery::execute()
         StorageInMemoryMetadata metadata = table->getInMemoryMetadata();
         alter_commands.validate(metadata, context);
         alter_commands.prepare(metadata);
-        table->checkAlterIsPossible(alter_commands, context.getSettingsRef());
+        table->checkAlterIsPossible(alter_commands, context);
         table->alter(alter_commands, context, alter_lock);
     }
 

src/Interpreters/InterpreterSelectQuery.h

@@ -89,6 +89,8 @@ public:
 
     static void addEmptySourceToQueryPlan(QueryPlan & query_plan, const Block & source_header, const SelectQueryInfo & query_info);
 
+    Names getRequiredColumns() { return required_columns; }
+
 private:
     InterpreterSelectQuery(
         const ASTPtr & query_ptr_,

src/Storages/IStorage.cpp

@@ -134,7 +134,7 @@ void IStorage::alter(const AlterCommands & params, const Context & context, Tabl
 }
 
 
-void IStorage::checkAlterIsPossible(const AlterCommands & commands, const Settings & /* settings */) const
+void IStorage::checkAlterIsPossible(const AlterCommands & commands, const Context & /* context */) const
 {
     for (const auto & command : commands)
     {
@@ -182,6 +182,24 @@ Names IStorage::getAllRegisteredNames() const
     return result;
 }
 
+NameDependencies IStorage::getDependentViewsByColumn(const Context & context) const
+{
+    NameDependencies name_deps;
+    auto dependencies = DatabaseCatalog::instance().getDependencies(storage_id);
+    for (const auto & depend_id : dependencies)
+    {
+        auto depend_table = DatabaseCatalog::instance().getTable(depend_id, context);
+        if (depend_table->getInMemoryMetadataPtr()->select.inner_query)
+        {
+            const auto & select_query = depend_table->getInMemoryMetadataPtr()->select.inner_query;
+            auto required_columns = InterpreterSelectQuery(select_query, context, SelectQueryOptions{}.noModify()).getRequiredColumns();
+            for (const auto & col_name : required_columns)
+                name_deps[col_name].push_back(depend_id.table_name);
+        }
+    }
+    return name_deps;
+}
+
 std::string PrewhereDAGInfo::dump() const
 {
     WriteBufferFromOwnString ss;

src/Storages/IStorage.h

@@ -57,6 +57,8 @@ struct StreamLocalLimits;
 class EnabledQuota;
 struct SelectQueryInfo;
 
+using NameDependencies = std::unordered_map<String, std::vector<String>>;
+
 struct ColumnSize
 {
     size_t marks = 0;
@@ -173,8 +175,10 @@ public:
     virtual NamesAndTypesList getVirtuals() const;
 
     Names getAllRegisteredNames() const override;
-protected:
 
+    NameDependencies getDependentViewsByColumn(const Context & context) const;
+
+protected:
     /// Returns whether the column is virtual - by default all columns are real.
     /// Initially reserved virtual column name may be shadowed by real column.
     bool isVirtualColumn(const String & column_name, const StorageMetadataPtr & metadata_snapshot) const;
@@ -362,7 +366,7 @@ public:
     /** Checks that alter commands can be applied to storage. For example, columns can be modified,
       * or primary key can be changes, etc.
       */
-    virtual void checkAlterIsPossible(const AlterCommands & commands, const Settings & settings) const;
+    virtual void checkAlterIsPossible(const AlterCommands & commands, const Context & context) const;
 
     /**
       * Checks that mutation commands can be applied to storage.

src/Storages/MergeTree/MergeTreeData.cpp

@@ -4,22 +4,22 @@
 #include <DataTypes/DataTypeDate.h>
 #include <DataTypes/DataTypeDateTime.h>
 #include <DataTypes/DataTypeEnum.h>
-#include <DataTypes/DataTypeUUID.h>
-#include <DataTypes/DataTypeNullable.h>
 #include <DataTypes/DataTypeLowCardinality.h>
+#include <DataTypes/DataTypeNullable.h>
+#include <DataTypes/DataTypeUUID.h>
 #include <DataTypes/NestedUtils.h>
 #include <Formats/FormatFactory.h>
-#include <Processors/Formats/InputStreamFromInputFormat.h>
 #include <Functions/FunctionFactory.h>
 #include <Functions/IFunction.h>
 #include <IO/ConcatReadBuffer.h>
 #include <IO/Operators.h>
 #include <IO/ReadBufferFromMemory.h>
 #include <IO/WriteBufferFromString.h>
+#include <Interpreters/Context.h>
 #include <Interpreters/ExpressionAnalyzer.h>
+#include <Interpreters/InterpreterSelectQuery.h>
 #include <Interpreters/PartLog.h>
 #include <Interpreters/TreeRewriter.h>
-#include <Interpreters/Context.h>
 #include <Interpreters/inplaceBlockConversions.h>
 #include <Parsers/ASTFunction.h>
 #include <Parsers/ASTLiteral.h>
@@ -29,10 +29,11 @@
 #include <Parsers/ExpressionListParsers.h>
 #include <Parsers/parseQuery.h>
 #include <Parsers/queryToString.h>
+#include <Processors/Formats/InputStreamFromInputFormat.h>
 #include <Storages/AlterCommands.h>
 #include <Storages/MergeTree/MergeTreeData.h>
-#include <Storages/MergeTree/MergeTreeDataPartInMemory.h>
 #include <Storages/MergeTree/MergeTreeDataPartCompact.h>
+#include <Storages/MergeTree/MergeTreeDataPartInMemory.h>
 #include <Storages/MergeTree/MergeTreeDataPartWide.h>
 #include <Storages/MergeTree/MergeTreeSequentialSource.h>
 #include <Storages/MergeTree/MergedBlockOutputStream.h>
@@ -1406,12 +1407,14 @@ void checkVersionColumnTypesConversion(const IDataType * old_type, const IDataTy
 
 }
 
-void MergeTreeData::checkAlterIsPossible(const AlterCommands & commands, const Settings & settings) const
+void MergeTreeData::checkAlterIsPossible(const AlterCommands & commands, const Context & context) const
 {
     /// Check that needed transformations can be applied to the list of columns without considering type conversions.
     StorageInMemoryMetadata new_metadata = getInMemoryMetadata();
     StorageInMemoryMetadata old_metadata = getInMemoryMetadata();
 
+    const auto & settings = context.getSettingsRef();
+
     if (!settings.allow_non_metadata_alters)
     {
 
@@ -1483,6 +1486,7 @@ void MergeTreeData::checkAlterIsPossible(const AlterCommands & commands, const S
         old_types.emplace(column.name, column.type.get());
 
     NamesAndTypesList columns_to_check_conversion;
+    auto name_deps = getDependentViewsByColumn(context);
     for (const AlterCommand & command : commands)
     {
         /// Just validate partition expression
@@ -1562,6 +1566,16 @@ void MergeTreeData::checkAlterIsPossible(const AlterCommands & commands, const S
                     "Trying to ALTER DROP key " + backQuoteIfNeed(command.column_name) + " column which is a part of key expression",
                     ErrorCodes::ALTER_OF_COLUMN_IS_FORBIDDEN);
             }
+
+            const auto & deps_mv = name_deps[command.column_name];
+            if (!deps_mv.empty())
+            {
+                throw Exception(
+                    "Trying to ALTER DROP column " + backQuoteIfNeed(command.column_name) + " which is referenced by materialized view "
+                        + toString(deps_mv),
+                    ErrorCodes::ALTER_OF_COLUMN_IS_FORBIDDEN);
+            }
+
             dropped_columns.emplace(command.column_name);
         }
         else if (command.isRequireMutationStage(getInMemoryMetadata()))

src/Storages/MergeTree/MergeTreeData.h

@@ -517,7 +517,7 @@ public:
     /// - all type conversions can be done.
     /// - columns corresponding to primary key, indices, sign, sampling expression and date are not affected.
     /// If something is wrong, throws an exception.
-    void checkAlterIsPossible(const AlterCommands & commands, const Settings & settings) const override;
+    void checkAlterIsPossible(const AlterCommands & commands, const Context & context) const override;
 
     /// Checks if the Mutation can be performed.
     /// (currently no additional checks: always ok)

src/Storages/StorageBuffer.cpp

@@ -58,6 +58,7 @@ namespace ErrorCodes
     extern const int LOGICAL_ERROR;
     extern const int INFINITE_LOOP;
     extern const int NUMBER_OF_ARGUMENTS_DOESNT_MATCH;
+    extern const int ALTER_OF_COLUMN_IS_FORBIDDEN;
 }
 
 
@@ -926,8 +927,9 @@ void StorageBuffer::reschedule()
     flush_handle->scheduleAfter(std::min(min, max) * 1000);
 }
 
-void StorageBuffer::checkAlterIsPossible(const AlterCommands & commands, const Settings & /* settings */) const
+void StorageBuffer::checkAlterIsPossible(const AlterCommands & commands, const Context & context) const
 {
+    auto name_deps = getDependentViewsByColumn(context);
     for (const auto & command : commands)
     {
         if (command.type != AlterCommand::Type::ADD_COLUMN && command.type != AlterCommand::Type::MODIFY_COLUMN
@@ -935,6 +937,17 @@ void StorageBuffer::checkAlterIsPossible(const AlterCommands & commands, const S
             throw Exception(
                 "Alter of type '" + alterTypeToString(command.type) + "' is not supported by storage " + getName(),
                 ErrorCodes::NOT_IMPLEMENTED);
+        if (command.type == AlterCommand::Type::DROP_COLUMN)
+        {
+            const auto & deps_mv = name_deps[command.column_name];
+            if (!deps_mv.empty())
+            {
+                throw Exception(
+                    "Trying to ALTER DROP column " + backQuoteIfNeed(command.column_name) + " which is referenced by materialized view "
+                        + toString(deps_mv),
+                    ErrorCodes::ALTER_OF_COLUMN_IS_FORBIDDEN);
+            }
+        }
     }
 }
 
@@ -971,7 +984,7 @@ std::optional<UInt64> StorageBuffer::totalBytes(const Settings & /*settings*/) c
 void StorageBuffer::alter(const AlterCommands & params, const Context & context, TableLockHolder &)
 {
     auto table_id = getStorageID();
-    checkAlterIsPossible(params, context.getSettingsRef());
+    checkAlterIsPossible(params, context);
     auto metadata_snapshot = getInMemoryMetadataPtr();
 
     /// Flush all buffers to storages, so that no non-empty blocks of the old

src/Storages/StorageBuffer.h

@@ -99,7 +99,7 @@ public:
 
     bool mayBenefitFromIndexForIn(const ASTPtr & left_in_operand, const Context & query_context, const StorageMetadataPtr & metadata_snapshot) const override;
 
-    void checkAlterIsPossible(const AlterCommands & commands, const Settings & /* settings */) const override;
+    void checkAlterIsPossible(const AlterCommands & commands, const Context & context) const override;
 
     /// The structure of the subordinate table is not checked and does not change.
     void alter(const AlterCommands & params, const Context & context, TableLockHolder & table_lock_holder) override;

src/Storages/StorageDistributed.cpp

@@ -84,6 +84,7 @@ namespace ErrorCodes
     extern const int TOO_MANY_ROWS;
     extern const int UNABLE_TO_SKIP_UNUSED_SHARDS;
     extern const int INVALID_SHARD_ID;
+    extern const int ALTER_OF_COLUMN_IS_FORBIDDEN;
 }
 
 namespace ActionLocks
@@ -577,8 +578,9 @@ BlockOutputStreamPtr StorageDistributed::write(const ASTPtr &, const StorageMeta
 }
 
 
-void StorageDistributed::checkAlterIsPossible(const AlterCommands & commands, const Settings & /* settings */) const
+void StorageDistributed::checkAlterIsPossible(const AlterCommands & commands, const Context & context) const
 {
+    auto name_deps = getDependentViewsByColumn(context);
     for (const auto & command : commands)
     {
         if (command.type != AlterCommand::Type::ADD_COLUMN
@@ -589,6 +591,17 @@ void StorageDistributed::checkAlterIsPossible(const AlterCommands & commands, co
 
             throw Exception("Alter of type '" + alterTypeToString(command.type) + "' is not supported by storage " + getName(),
                 ErrorCodes::NOT_IMPLEMENTED);
+        if (command.type == AlterCommand::DROP_COLUMN)
+        {
+            const auto & deps_mv = name_deps[command.column_name];
+            if (!deps_mv.empty())
+            {
+                throw Exception(
+                    "Trying to ALTER DROP column " + backQuoteIfNeed(command.column_name) + " which is referenced by materialized view "
+                        + toString(deps_mv),
+                    ErrorCodes::ALTER_OF_COLUMN_IS_FORBIDDEN);
+            }
+        }
     }
 }
 
@@ -596,7 +609,7 @@ void StorageDistributed::alter(const AlterCommands & params, const Context & con
 {
     auto table_id = getStorageID();
 
-    checkAlterIsPossible(params, context.getSettingsRef());
+    checkAlterIsPossible(params, context);
     StorageInMemoryMetadata new_metadata = getInMemoryMetadata();
     params.apply(new_metadata, context);
     DatabaseCatalog::instance().getDatabase(table_id.database_name)->alterTable(context, table_id, new_metadata);

src/Storages/StorageDistributed.h

@@ -85,7 +85,7 @@ public:
     void rename(const String & new_path_to_table_data, const StorageID & new_table_id) override;
     void renameOnDisk(const String & new_path_to_table_data);
 
-    void checkAlterIsPossible(const AlterCommands & commands, const Settings & /* settings */) const override;
+    void checkAlterIsPossible(const AlterCommands & commands, const Context & context) const override;
 
     /// in the sub-tables, you need to manually add and delete columns
     /// the structure of the sub-table is not checked

src/Storages/StorageMaterializedView.cpp

@@ -296,8 +296,9 @@ void StorageMaterializedView::alter(
 }
 
 
-void StorageMaterializedView::checkAlterIsPossible(const AlterCommands & commands, const Settings & settings) const
+void StorageMaterializedView::checkAlterIsPossible(const AlterCommands & commands, const Context & context) const
 {
+    const auto & settings = context.getSettingsRef();
     if (settings.allow_experimental_alter_materialized_view_structure)
     {
         for (const auto & command : commands)

src/Storages/StorageMaterializedView.h

@@ -54,7 +54,7 @@ public:
 
     void checkMutationIsPossible(const MutationCommands & commands, const Settings & settings) const override;
 
-    void checkAlterIsPossible(const AlterCommands & commands, const Settings & settings) const override;
+    void checkAlterIsPossible(const AlterCommands & commands, const Context & context) const override;
 
     Pipe alterPartition(const StorageMetadataPtr & metadata_snapshot, const PartitionCommands & commands, const Context & context) override;
 

src/Storages/StorageMerge.cpp

@@ -37,6 +37,7 @@ namespace ErrorCodes
     extern const int ILLEGAL_PREWHERE;
     extern const int NUMBER_OF_ARGUMENTS_DOESNT_MATCH;
     extern const int SAMPLING_NOT_SUPPORTED;
+    extern const int ALTER_OF_COLUMN_IS_FORBIDDEN;
 }
 
 namespace
@@ -472,8 +473,9 @@ DatabaseTablesIteratorPtr StorageMerge::getDatabaseIterator(const Context & cont
 }
 
 
-void StorageMerge::checkAlterIsPossible(const AlterCommands & commands, const Settings & /* settings */) const
+void StorageMerge::checkAlterIsPossible(const AlterCommands & commands, const Context & context) const
 {
+    auto name_deps = getDependentViewsByColumn(context);
     for (const auto & command : commands)
     {
         if (command.type != AlterCommand::Type::ADD_COLUMN && command.type != AlterCommand::Type::MODIFY_COLUMN
@@ -481,6 +483,17 @@ void StorageMerge::checkAlterIsPossible(const AlterCommands & commands, const Se
             throw Exception(
                 "Alter of type '" + alterTypeToString(command.type) + "' is not supported by storage " + getName(),
                 ErrorCodes::NOT_IMPLEMENTED);
+        if (command.type == AlterCommand::Type::DROP_COLUMN)
+        {
+            const auto & deps_mv = name_deps[command.column_name];
+            if (!deps_mv.empty())
+            {
+                throw Exception(
+                    "Trying to ALTER DROP column " + backQuoteIfNeed(command.column_name) + " which is referenced by materialized view "
+                        + toString(deps_mv),
+                    ErrorCodes::ALTER_OF_COLUMN_IS_FORBIDDEN);
+            }
+        }
     }
 }
 

src/Storages/StorageMerge.h

@@ -38,7 +38,7 @@ public:
         size_t max_block_size,
         unsigned num_streams) override;
 
-    void checkAlterIsPossible(const AlterCommands & commands, const Settings & /* settings */) const override;
+    void checkAlterIsPossible(const AlterCommands & commands, const Context & context) const override;
 
     /// you need to add and remove columns in the sub-tables manually
     /// the structure of sub-tables is not checked

src/Storages/StorageNull.cpp

@@ -16,6 +16,7 @@ namespace ErrorCodes
 {
     extern const int NOT_IMPLEMENTED;
     extern const int NUMBER_OF_ARGUMENTS_DOESNT_MATCH;
+    extern const int ALTER_OF_COLUMN_IS_FORBIDDEN;
 }
 
 
@@ -35,8 +36,9 @@ void registerStorageNull(StorageFactory & factory)
     });
 }
 
-void StorageNull::checkAlterIsPossible(const AlterCommands & commands, const Settings & /* settings */) const
+void StorageNull::checkAlterIsPossible(const AlterCommands & commands, const Context & context) const
 {
+    auto name_deps = getDependentViewsByColumn(context);
     for (const auto & command : commands)
     {
         if (command.type != AlterCommand::Type::ADD_COLUMN && command.type != AlterCommand::Type::MODIFY_COLUMN
@@ -44,6 +46,17 @@ void StorageNull::checkAlterIsPossible(const AlterCommands & commands, const Set
             throw Exception(
                 "Alter of type '" + alterTypeToString(command.type) + "' is not supported by storage " + getName(),
                 ErrorCodes::NOT_IMPLEMENTED);
+        if (command.type == AlterCommand::DROP_COLUMN)
+        {
+            const auto & deps_mv = name_deps[command.column_name];
+            if (!deps_mv.empty())
+            {
+                throw Exception(
+                    "Trying to ALTER DROP column " + backQuoteIfNeed(command.column_name) + " which is referenced by materialized view "
+                        + toString(deps_mv),
+                    ErrorCodes::ALTER_OF_COLUMN_IS_FORBIDDEN);
+            }
+        }
     }
 }
 

src/Storages/StorageNull.h

@@ -41,7 +41,7 @@ public:
         return std::make_shared<NullBlockOutputStream>(metadata_snapshot->getSampleBlock());
     }
 
-    void checkAlterIsPossible(const AlterCommands & commands, const Settings & /* settings */) const override;
+    void checkAlterIsPossible(const AlterCommands & commands, const Context & context) const override;
 
     void alter(const AlterCommands & params, const Context & context, TableLockHolder & table_lock_holder) override;
 

src/Storages/StorageProxy.h

@@ -97,9 +97,9 @@ public:
         IStorage::setInMemoryMetadata(getNested()->getInMemoryMetadata());
     }
 
-    void checkAlterIsPossible(const AlterCommands & commands, const Settings & settings) const override
+    void checkAlterIsPossible(const AlterCommands & commands, const Context & context) const override
     {
-        getNested()->checkAlterIsPossible(commands, settings);
+        getNested()->checkAlterIsPossible(commands, context);
     }
 
     Pipe alterPartition(

tests/queries/0_stateless/01746_forbid_drop_column_referenced_by_mv.sql

@@ -0,0 +1,172 @@
+-- MergeTree
+DROP TABLE IF EXISTS `01746_merge_tree`;
+CREATE TABLE `01746_merge_tree`
+(
+    `n1` Int8,
+    `n2` Int8,
+    `n3` Int8,
+    `n4` Int8
+)
+ENGINE = MergeTree
+ORDER BY n1;
+
+DROP TABLE IF EXISTS `01746_merge_tree_mv`;
+CREATE MATERIALIZED VIEW `01746_merge_tree_mv`
+ENGINE = Memory AS
+SELECT
+    n2,
+    n3
+FROM `01746_merge_tree`;
+
+ALTER TABLE `01746_merge_tree`
+    DROP COLUMN n3;  -- { serverError 524 }
+
+ALTER TABLE `01746_merge_tree`
+    DROP COLUMN n2;  -- { serverError 524 }
+
+-- ok
+ALTER TABLE `01746_merge_tree`
+    DROP COLUMN n4;
+
+DROP TABLE `01746_merge_tree`;
+DROP TABLE `01746_merge_tree_mv`;
+
+-- Null 
+DROP TABLE IF EXISTS `01746_null`;
+CREATE TABLE `01746_null`
+(
+    `n1` Int8,
+    `n2` Int8,
+    `n3` Int8
+)
+ENGINE = Null;
+
+DROP TABLE IF EXISTS `01746_null_mv`;
+CREATE MATERIALIZED VIEW `01746_null_mv`
+ENGINE = Memory AS
+SELECT
+    n1,
+    n2
+FROM `01746_null`;
+
+ALTER TABLE `01746_null`
+    DROP COLUMN n1; -- { serverError 524 }
+
+ALTER TABLE `01746_null`
+    DROP COLUMN n2; -- { serverError 524 }
+
+-- ok
+ALTER TABLE `01746_null`
+    DROP COLUMN n3;
+
+DROP TABLE `01746_null`;
+DROP TABLE `01746_null_mv`;
+
+-- Distributed
+
+DROP TABLE IF EXISTS `01746_local`;
+CREATE TABLE `01746_local`
+(
+    `n1` Int8,
+    `n2` Int8,
+    `n3` Int8
+)
+ENGINE = Memory;
+
+DROP TABLE IF EXISTS `01746_dist`;
+CREATE TABLE `01746_dist` AS `01746_local`
+ENGINE = Distributed('test_shard_localhost', currentDatabase(), `01746_local`, rand());
+
+DROP TABLE IF EXISTS `01746_dist_mv`;
+CREATE MATERIALIZED VIEW `01746_dist_mv`
+ENGINE = Memory AS
+SELECT
+    n1,
+    n2
+FROM `01746_dist`;
+
+ALTER TABLE `01746_dist`
+    DROP COLUMN n1; -- { serverError 524 }
+
+ALTER TABLE `01746_dist`
+    DROP COLUMN n2; -- { serverError 524 }
+
+-- ok
+ALTER TABLE `01746_dist`
+    DROP COLUMN n3;
+
+DROP TABLE `01746_local`;
+DROP TABLE `01746_dist`;
+DROP TABLE `01746_dist_mv`;
+
+-- Merge
+DROP TABLE IF EXISTS `01746_merge_t`;
+CREATE TABLE `01746_merge_t`
+(
+    `n1` Int8,
+    `n2` Int8,
+    `n3` Int8
+)
+ENGINE = Memory;
+
+DROP TABLE IF EXISTS `01746_merge`;
+CREATE TABLE `01746_merge` AS `01746_merge_t`
+ENGINE = Merge(currentDatabase(), '01746_merge_t');
+
+DROP TABLE IF EXISTS `01746_merge_mv`;
+CREATE MATERIALIZED VIEW `01746_merge_mv`
+ENGINE = Memory AS
+SELECT
+    n1,
+    n2
+FROM `01746_merge`;
+
+ALTER TABLE `01746_merge`
+    DROP COLUMN n1; -- { serverError 524 }
+
+ALTER TABLE `01746_merge`
+    DROP COLUMN n2; -- { serverError 524 }
+
+-- ok
+ALTER TABLE `01746_merge`
+    DROP COLUMN n3;
+
+DROP TABLE `01746_merge_t`;
+DROP TABLE `01746_merge`;
+DROP TABLE `01746_merge_mv`;
+
+-- Buffer
+DROP TABLE IF EXISTS `01746_buffer_t`;
+CREATE TABLE `01746_buffer_t`
+(
+    `n1` Int8,
+    `n2` Int8,
+    `n3` Int8
+)
+ENGINE = Memory;
+
+DROP TABLE IF EXISTS `01746_buffer`;
+CREATE TABLE `01746_buffer` AS `01746_buffer_t`
+ENGINE = Buffer(currentDatabase(), `01746_buffer_t`, 16, 10, 100, 10000, 1000000, 10000000, 100000000);
+
+DROP TABLE IF EXISTS `01746_buffer_mv`;
+CREATE MATERIALIZED VIEW `01746_buffer_mv`
+ENGINE = Memory AS
+SELECT
+    n1,
+    n2
+FROM `01746_buffer`;
+
+ALTER TABLE `01746_buffer`
+    DROP COLUMN n1; -- { serverError 524 }
+
+ALTER TABLE `01746_buffer`
+    DROP COLUMN n2; -- { serverError 524 }
+
+-- ok
+ALTER TABLE `01746_buffer`
+    DROP COLUMN n3;
+
+DROP TABLE `01746_buffer_t`;
+DROP TABLE `01746_buffer`;
+DROP TABLE `01746_buffer_mv`;