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#pragma once
#include <optional>
#include <Core/NamesAndTypes.h>
#include <Storages/IStorage_fwd.h>
#include <Storages/StorageInMemoryMetadata.h>
#include <Storages/MutationCommands.h>
#include <Storages/ColumnsDescription.h>
#include <Common/SettingsChanges.h>
namespace DB
{
class ASTAlterCommand;
class IDatabase;
using DatabasePtr = std::shared_ptr<IDatabase>;
/// 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<String> 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<String> 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<AlterCommand> 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<MutationCommand> tryConvertToMutationCommand(StorageInMemoryMetadata & metadata, ContextPtr context) const;
};
class Context;
/// Vector of AlterCommand with several additional functions
class AlterCommands : public std::vector<AlterCommand>
{
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 StoragePtr & table, 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, bool with_alters=false) const;
/// Check if commands have any inverted index
static bool hasInvertedIndex(const StorageInMemoryMetadata & metadata);
};
}
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