More general

dbms/src/Storages/IStorage.cpp

@@ -1,6 +1,8 @@
 #include <Storages/IStorage.h>
 
 #include <Storages/AlterCommands.h>
+#include <Parsers/ASTCreateQuery.h>
+#include <Parsers/ASTSetQuery.h>
 
 #include <sparsehash/dense_hash_map>
 #include <sparsehash/dense_hash_set>
@@ -19,6 +21,7 @@ namespace ErrorCodes
     extern const int NOT_FOUND_COLUMN_IN_BLOCK;
     extern const int TYPE_MISMATCH;
     extern const int SETTINGS_ARE_NOT_SUPPORTED;
+    extern const int UNKNOWN_SETTING;
 }
 
 IStorage::IStorage(ColumnsDescription columns_)
@@ -295,7 +298,9 @@ bool IStorage::isVirtualColumn(const String & column_name) const
 
 bool IStorage::hasSetting(const String & /* setting_name */) const
 {
-    throw Exception("Storage '" + getName() + "' doesn't support settings.", ErrorCodes::SETTINGS_ARE_NOT_SUPPORTED);
+    if (!supportsSettings())
+        throw Exception("Storage '" + getName() + "' doesn't support settings.", ErrorCodes::SETTINGS_ARE_NOT_SUPPORTED);
+    return false;
 }
 
 TableStructureReadLockHolder IStorage::lockStructureForShare(bool will_add_new_data, const String & query_id)
@@ -352,6 +357,39 @@ TableStructureWriteLockHolder IStorage::lockExclusively(const String & query_id)
     return result;
 }
 
+
+void IStorage::alterSettings(
+    const SettingsChanges & new_changes,
+    const String & current_database_name,
+    const String & current_table_name,
+    const Context & context,
+    TableStructureWriteLockHolder & /* table_lock_holder */)
+{
+    IDatabase::ASTModifier storage_modifier = [&] (IAST & ast)
+    {
+        if (!new_changes.empty())
+        {
+            auto & storage_changes = ast.as<ASTStorage &>().settings->changes;
+            /// Make storage settings unique
+            for (const auto & change : new_changes)
+            {
+                if (hasSetting(change.name))
+                {
+                    auto finder = [&change] (const SettingChange & c) { return c.name == change.name;};
+                    if (auto it = std::find_if(storage_changes.begin(), storage_changes.end(), finder); it != storage_changes.end())
+                        it->value = change.value;
+                    else
+                        storage_changes.push_back(change);
+                }
+                else
+                    throw Exception{"Storage '" + getName() + "' doesn't have setting '" + change.name + "'", ErrorCodes::UNKNOWN_SETTING};
+            }
+        }
+    };
+    context.getDatabase(current_database_name)->alterTable(context, current_table_name, getColumns(), getIndices(), storage_modifier);
+}
+
+
 void IStorage::alter(
     const AlterCommands & params,
     const String & database_name,
@@ -359,12 +397,17 @@ void IStorage::alter(
     const Context & context,
     TableStructureWriteLockHolder & table_lock_holder)
 {
-    for (const auto & param : params)
+    if (params.isSettingsAlter())
     {
-        if (param.isMutable())
-            throw Exception("Method alter supports only change comment of column for storage " + getName(), ErrorCodes::NOT_IMPLEMENTED);
+        SettingsChanges new_changes;
+        params.applyForSettingsOnly(new_changes);
+        alterSettings(new_changes, database_name, table_name, context, table_lock_holder);
+        return;
     }
 
+    if (params.isMutable())
+        throw Exception("Method alter supports only change comment of column for storage " + getName(), ErrorCodes::NOT_IMPLEMENTED);
+
     lockStructureExclusively(table_lock_holder, context.getCurrentQueryId());
     auto new_columns = getColumns();
     auto new_indices = getIndices();

dbms/src/Storages/IStorage.h

@@ -12,6 +12,7 @@
 #include <Common/ActionLock.h>
 #include <Common/Exception.h>
 #include <Common/RWLock.h>
+#include <Common/SettingsChanges.h>
 
 #include <optional>
 #include <shared_mutex>
@@ -95,6 +96,9 @@ public:
     /// Returns true if the storage supports deduplication of inserted data blocks.
     virtual bool supportsDeduplication() const { return false; }
 
+    /// Returns true if the storage supports settings.
+    virtual bool supportsSettings() const { return false; }
+
     /// Optional size information of each physical column.
     /// Currently it's only used by the MergeTree family for query optimizations.
     using ColumnSizeByName = std::unordered_map<std::string, ColumnSize>;
@@ -252,6 +256,15 @@ public:
         throw Exception("Partition operations are not supported by storage " + getName(), ErrorCodes::NOT_IMPLEMENTED);
     }
 
+    /** ALTER table settings if possible. Otherwise throws exception.
+     */
+    virtual void alterSettings(
+        const SettingsChanges & new_changes,
+        const String & current_database_name,
+        const String & current_table_name,
+        const Context & context,
+        TableStructureWriteLockHolder & table_lock_holder);
+
     /** Perform any background work. For example, combining parts in a MergeTree type table.
       * Returns whether any work has been done.
       */

dbms/src/Storages/Kafka/StorageKafka.cpp

@@ -40,6 +40,7 @@ namespace ErrorCodes
     extern const int LOGICAL_ERROR;
     extern const int BAD_ARGUMENTS;
     extern const int NUMBER_OF_ARGUMENTS_DOESNT_MATCH;
+    extern const int UNSUPPORTED_METHOD;
 }
 
 namespace
@@ -388,6 +389,22 @@ bool StorageKafka::streamToViews()
 }
 
 
+bool StorageKafka::hasSetting(const String & setting_name) const
+{
+    return KafkaSettings::findIndex(setting_name) != KafkaSettings::npos;
+}
+
+void StorageKafka::alterSettings(
+    const SettingsChanges & /* new_changes */,
+    const String & /* current_database_name */,
+    const String & /* current_table_name */,
+    const Context & /* context */,
+    TableStructureWriteLockHolder & /* table_lock_holder */)
+{
+    throw Exception("Storage '" + getName() + "' doesn't support settings alter", ErrorCodes::UNSUPPORTED_METHOD);
+}
+
+
 void registerStorageKafka(StorageFactory & factory)
 {
     factory.registerStorage("Kafka", [](const StorageFactory::Arguments & args)

dbms/src/Storages/Kafka/StorageKafka.h

@@ -24,6 +24,7 @@ public:
     std::string getName() const override { return "Kafka"; }
     std::string getTableName() const override { return table_name; }
     std::string getDatabaseName() const override { return database_name; }
+    bool supportsSettings() const override { return true; }
 
     void startup() override;
     void shutdown() override;
@@ -50,6 +51,15 @@ public:
     const auto & getSchemaName() const { return schema_name; }
     const auto & skipBroken() const { return skip_broken; }
 
+    bool hasSetting(const String & setting_name) const override;
+
+    void alterSettings(
+        const SettingsChanges & new_changes,
+        const String & current_database_name,
+        const String & current_table_name,
+        const Context & context,
+        TableStructureWriteLockHolder & table_lock_holder) override;
+
 protected:
     StorageKafka(
         const std::string & table_name_,

dbms/src/Storages/MergeTree/MergeTreeData.cpp

@@ -1588,26 +1588,10 @@ void MergeTreeData::alterSettings(
         const String & current_database_name,
         const String & current_table_name,
         const Context & context,
-        TableStructureWriteLockHolder & /* table_lock_holder */)
+        TableStructureWriteLockHolder & table_lock_holder)
 {
     settings.updateFromChanges(new_changes);
-    IDatabase::ASTModifier storage_modifier = [&] (IAST & ast)
-    {
-        if (!new_changes.empty())
-        {
-            auto & storage_changes = ast.as<ASTStorage &>().settings->changes;
-            /// Make storage settings unique
-            for (const auto & change : new_changes)
-            {
-                auto finder = [&change] (const SettingChange & c) { return c.name == change.name;};
-                if (auto it = std::find_if(storage_changes.begin(), storage_changes.end(), finder); it != storage_changes.end())
-                    it->value = change.value;
-                else
-                    storage_changes.push_back(change);
-            }
-        }
-    };
-    context.getDatabase(current_database_name)->alterTable(context, current_table_name, getColumns(), getIndices(), storage_modifier);
+    IStorage::alterSettings(new_changes, current_database_name, current_table_name, context, table_lock_holder);
 }
 
 bool MergeTreeData::hasSetting(const String & setting_name) const
@@ -2245,7 +2229,7 @@ std::optional<Int64> MergeTreeData::getMinPartDataVersion() const
 }
 
 
-void MergeTreeData::delayInsertOrThrowIfNeeded(Poco::Event *until) const
+void MergeTreeData::delayInsertOrThrowIfNeeded(Poco::Event * until) const
 {
     const size_t parts_count_in_total = getPartsCount();
     if (parts_count_in_total >= settings.max_parts_in_total)

dbms/src/Storages/MergeTree/MergeTreeData.h

@@ -342,6 +342,8 @@ public:
             || merging_params.mode == MergingParams::VersionedCollapsing;
     }
 
+    bool supportsSettings() const override { return true; }
+
     bool mayBenefitFromIndexForIn(const ASTPtr & left_in_operand, const Context &) const override;
 
     NameAndTypePair getColumn(const String & column_name) const override
@@ -516,7 +518,7 @@ public:
            const String & current_database_name,
            const String & current_table_name,
            const Context & context,
-           TableStructureWriteLockHolder & table_lock_holder);
+           TableStructureWriteLockHolder & table_lock_holder) override;
 
     /// All MergeTreeData children have settings.
     bool hasSetting(const String & setting_name) const override;