ALTER MODIFY ORDER BY syntax [#CLICKHOUSE-3859]

dbms/src/Parsers/ASTAlterQuery.cpp

@@ -30,6 +30,11 @@ ASTPtr ASTAlterCommand::clone() const
         res->primary_key = primary_key->clone();
         res->children.push_back(res->primary_key);
     }
+    if (sorting_key)
+    {
+        res->sorting_key = sorting_key->clone();
+        res->children.push_back(res->sorting_key);
+    }
     if (partition)
     {
         res->partition = partition->clone();
@@ -84,6 +89,13 @@ void ASTAlterCommand::formatImpl(
         primary_key->formatImpl(settings, state, frame);
         settings.ostr << ")";
     }
+    else if (type == ASTAlterCommand::MODIFY_ORDER_BY)
+    {
+        settings.ostr << (settings.hilite ? hilite_keyword : "") << indent_str << "MODIFY ORDER BY " << (settings.hilite ? hilite_none : "");
+        settings.ostr << "(";
+        sorting_key->formatImpl(settings, state, frame);
+        settings.ostr << ")";
+    }
     else if (type == ASTAlterCommand::DROP_PARTITION)
     {
         settings.ostr << (settings.hilite ? hilite_keyword : "") << indent_str << (detach ? "DETACH" : "DROP") << " PARTITION "

dbms/src/Parsers/ASTAlterQuery.h

@@ -25,6 +25,7 @@ public:
         DROP_COLUMN,
         MODIFY_COLUMN,
         MODIFY_PRIMARY_KEY,
+        MODIFY_ORDER_BY,
 
         DROP_PARTITION,
         ATTACH_PARTITION,
@@ -55,6 +56,10 @@ public:
      */
     ASTPtr primary_key;
 
+    /** For MODIFY ORDER BY
+     */
+    ASTPtr sorting_key;
+
     /** Used in DROP PARTITION and ATTACH PARTITION FROM queries.
      *  The value or ID of the partition is stored here.
      */

dbms/src/Parsers/ParserAlterQuery.cpp

@@ -24,6 +24,7 @@ bool ParserAlterCommand::parseImpl(Pos & pos, ASTPtr & node, Expected & expected
     ParserKeyword s_clear_column("CLEAR COLUMN");
     ParserKeyword s_modify_column("MODIFY COLUMN");
     ParserKeyword s_modify_primary_key("MODIFY PRIMARY KEY");
+    ParserKeyword s_modify_order_by("MODIFY ORDER BY");
 
     ParserKeyword s_attach_partition("ATTACH PARTITION");
     ParserKeyword s_detach_partition("DETACH PARTITION");
@@ -200,6 +201,21 @@ bool ParserAlterCommand::parseImpl(Pos & pos, ASTPtr & node, Expected & expected
 
         command->type = ASTAlterCommand::MODIFY_PRIMARY_KEY;
     }
+    else if (s_modify_order_by.ignore(pos, expected))
+    {
+        if (pos->type != TokenType::OpeningRoundBracket)
+            return false;
+        ++pos;
+
+        if (!ParserNotEmptyExpressionList(false).parse(pos, command->sorting_key, expected))
+            return false;
+
+        if (pos->type != TokenType::ClosingRoundBracket)
+            return false;
+        ++pos;
+
+        command->type = ASTAlterCommand::MODIFY_ORDER_BY;
+    }
     else if (s_delete_where.ignore(pos, expected))
     {
         if (!parser_exp_elem.parse(pos, command->predicate, expected))

dbms/src/Storages/AlterCommands.cpp

@@ -90,6 +90,13 @@ std::optional<AlterCommand> AlterCommand::parse(const ASTAlterCommand * command_
         command.primary_key = command_ast->primary_key;
         return command;
     }
+    else if (command_ast->type == ASTAlterCommand::MODIFY_ORDER_BY)
+    {
+        AlterCommand command;
+        command.type = AlterCommand::MODIFY_ORDER_BY;
+        command.sorting_key = command_ast->sorting_key;
+        return command;
+    }
     else
         return {};
 }
@@ -232,7 +239,7 @@ void AlterCommand::apply(ColumnsDescription & columns_description) const
             /// both old and new columns have default expression, update it
             columns_description.defaults[column_name].expression = default_expression;
     }
-    else if (type == MODIFY_PRIMARY_KEY)
+    else if (type == MODIFY_PRIMARY_KEY || type == MODIFY_ORDER_BY)
     {
         /// This have no relation to changing the list of columns.
         /// TODO Check that all columns exist, that only columns with constant defaults are added.

dbms/src/Storages/AlterCommands.h

@@ -21,6 +21,7 @@ struct AlterCommand
         DROP_COLUMN,
         MODIFY_COLUMN,
         MODIFY_PRIMARY_KEY,
+        MODIFY_ORDER_BY,
     };
 
     Type type;
@@ -42,6 +43,9 @@ struct AlterCommand
     /// For MODIFY_PRIMARY_KEY
     ASTPtr primary_key;
 
+    /// For MODIFY_ORDER_BY
+    ASTPtr sorting_key;
+
     AlterCommand() = default;
     AlterCommand(const Type type, const String & column_name, const DataTypePtr & data_type,
                  const ColumnDefaultKind default_kind, const ASTPtr & default_expression,