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