#pragma once #include #include #include #include #include #include #include namespace DB { class ASTAlterCommand; class IDatabase; using DatabasePtr = std::shared_ptr; /// Operation from the ALTER query (except for manipulation with PART/PARTITION). /// Adding Nested columns is not expanded to add individual columns. struct AlterCommand { /// The AST of the whole command ASTPtr ast; enum Type { UNKNOWN, ADD_COLUMN, DROP_COLUMN, MODIFY_COLUMN, COMMENT_COLUMN, MODIFY_ORDER_BY, MODIFY_SAMPLE_BY, ADD_INDEX, DROP_INDEX, ADD_CONSTRAINT, DROP_CONSTRAINT, ADD_PROJECTION, DROP_PROJECTION, MODIFY_TTL, MODIFY_SETTING, RESET_SETTING, MODIFY_QUERY, RENAME_COLUMN, REMOVE_TTL, MODIFY_DATABASE_SETTING, COMMENT_TABLE, REMOVE_SAMPLE_BY, }; /// Which property user wants to remove from column enum class RemoveProperty { NO_PROPERTY, /// Default specifiers DEFAULT, MATERIALIZED, ALIAS, /// Other properties COMMENT, CODEC, TTL }; Type type = UNKNOWN; String column_name; /// For DROP/CLEAR COLUMN/INDEX ... IN PARTITION ASTPtr partition; /// For ADD and MODIFY, a new column type. DataTypePtr data_type = nullptr; ColumnDefaultKind default_kind{}; ASTPtr default_expression{}; /// For COMMENT column or table std::optional comment; /// For ADD or MODIFY - after which column to add a new one. If an empty string, add to the end. String after_column; /// For ADD_COLUMN, MODIFY_COLUMN, ADD_INDEX - Add to the begin if it is true. bool first = false; /// For DROP_COLUMN, MODIFY_COLUMN, COMMENT_COLUMN, RESET_SETTING bool if_exists = false; /// For ADD_COLUMN bool if_not_exists = false; /// For MODIFY_ORDER_BY ASTPtr order_by = nullptr; /// For MODIFY_SAMPLE_BY ASTPtr sample_by = nullptr; /// For ADD INDEX ASTPtr index_decl = nullptr; String after_index_name; /// For ADD/DROP INDEX String index_name; // For ADD CONSTRAINT ASTPtr constraint_decl = nullptr; // For ADD/DROP CONSTRAINT String constraint_name; /// For ADD PROJECTION ASTPtr projection_decl = nullptr; String after_projection_name; /// For ADD/DROP PROJECTION String projection_name; /// For MODIFY TTL ASTPtr ttl = nullptr; /// indicates that this command should not be applied, for example in case of if_exists=true and column doesn't exist. bool ignore = false; /// Clear columns or index (don't drop from metadata) bool clear = false; /// For ADD and MODIFY ASTPtr codec = nullptr; /// For MODIFY SETTING SettingsChanges settings_changes; /// For RESET SETTING std::set settings_resets; /// For MODIFY_QUERY ASTPtr select = nullptr; /// Target column name String rename_to; /// What to remove from column (or TTL) RemoveProperty to_remove = RemoveProperty::NO_PROPERTY; static std::optional parse(const ASTAlterCommand * command); void apply(StorageInMemoryMetadata & metadata, ContextPtr context) const; /// Check that alter command require data modification (mutation) to be /// executed. For example, cast from Date to UInt16 type can be executed /// without any data modifications. But column drop or modify from UInt16 to /// UInt32 require data modification. bool isRequireMutationStage(const StorageInMemoryMetadata & metadata) const; /// Checks that only settings changed by alter bool isSettingsAlter() const; /// Checks that only comment changed by alter bool isCommentAlter() const; /// Checks that any TTL changed by alter bool isTTLAlter(const StorageInMemoryMetadata & metadata) const; /// Command removing some property from column or table bool isRemovingProperty() const; /// If possible, convert alter command to mutation command. In other case /// return empty optional. Some storages may execute mutations after /// metadata changes. std::optional tryConvertToMutationCommand(StorageInMemoryMetadata & metadata, ContextPtr context) const; }; class Context; /// Vector of AlterCommand with several additional functions class AlterCommands : public std::vector { private: bool prepared = false; public: /// Validate that commands can be applied to metadata. /// Checks that all columns exist and dependencies between them. /// This check is lightweight and base only on metadata. /// More accurate check have to be performed with storage->checkAlterIsPossible. void validate(const StorageInMemoryMetadata & metadata, ContextPtr context) const; /// Prepare alter commands. Set ignore flag to some of them and set some /// parts to commands from storage's metadata (for example, absent default) void prepare(const StorageInMemoryMetadata & metadata); /// Apply all alter command in sequential order to storage metadata. /// Commands have to be prepared before apply. void apply(StorageInMemoryMetadata & metadata, ContextPtr context) const; /// At least one command modify settings. bool hasSettingsAlterCommand() const; /// All commands modify settings only. bool isSettingsAlter() const; /// All commands modify comments only. bool isCommentAlter() const; /// Return mutation commands which some storages may execute as part of /// alter. If alter can be performed as pure metadata update, than result is /// empty. If some TTL changes happened than, depending on materialize_ttl /// additional mutation command (MATERIALIZE_TTL) will be returned. MutationCommands getMutationCommands(StorageInMemoryMetadata metadata, bool materialize_ttl, ContextPtr context) const; }; }