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100 lines
3.9 KiB
C++
100 lines
3.9 KiB
C++
#pragma once
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#include <DataStreams/IBlockInputStream.h>
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#include <Interpreters/ExpressionActions.h>
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#include <Interpreters/ExpressionAnalyzer.h>
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#include <Interpreters/InterpreterSelectQuery.h>
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#include <Storages/IStorage_fwd.h>
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#include <Storages/MutationCommands.h>
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namespace DB
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{
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class Context;
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/// Return false if the data isn't going to be changed by mutations.
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bool isStorageTouchedByMutations(StoragePtr storage, const std::vector<MutationCommand> & commands, Context context_copy);
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/// Create an input stream that will read data from storage and apply mutation commands (UPDATEs, DELETEs, MATERIALIZEs)
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/// to this data.
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class MutationsInterpreter
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{
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public:
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/// Storage to mutate, array of mutations commands and context. If you really want to execute mutation
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/// use can_execute = true, in other cases (validation, amount of commands) it can be false
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MutationsInterpreter(StoragePtr storage_, MutationCommands commands_, const Context & context_, bool can_execute_);
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void validate(TableStructureReadLockHolder & table_lock_holder);
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size_t evaluateCommandsSize();
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/// The resulting stream will return blocks containing only changed columns and columns, that we need to recalculate indices.
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BlockInputStreamPtr execute(TableStructureReadLockHolder & table_lock_holder);
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/// Only changed columns.
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const Block & getUpdatedHeader() const;
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private:
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ASTPtr prepare(bool dry_run);
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struct Stage;
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ASTPtr prepareInterpreterSelectQuery(std::vector<Stage> &prepared_stages, bool dry_run);
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BlockInputStreamPtr addStreamsForLaterStages(const std::vector<Stage> & prepared_stages, BlockInputStreamPtr in) const;
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std::optional<SortDescription> getStorageSortDescriptionIfPossible(const Block & header) const;
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StoragePtr storage;
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MutationCommands commands;
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Context context;
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bool can_execute;
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ASTPtr mutation_ast;
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/// We have to store interpreter because it use own copy of context
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/// and some streams from execute method may use it.
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std::unique_ptr<InterpreterSelectQuery> select_interpreter;
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/// A sequence of mutation commands is executed as a sequence of stages. Each stage consists of several
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/// filters, followed by updating values of some columns. Commands can reuse expressions calculated by the
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/// previous commands in the same stage, but at the end of each stage intermediate columns are thrown away
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/// (they may contain wrong values because the column values have been updated).
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///
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/// If an UPDATE command changes some columns that some MATERIALIZED columns depend on, a stage to
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/// recalculate these columns is added.
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///
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/// Each stage has output_columns that contain columns that are changed at the end of that stage
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/// plus columns needed for the next mutations.
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///
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/// First stage is special: it can contain only filters and is executed using InterpreterSelectQuery
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/// to take advantage of table indexes (if there are any). It's necessary because all mutations have
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/// `WHERE clause` part.
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struct Stage
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{
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Stage(const Context & context_) : expressions_chain(context_) {}
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ASTs filters;
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std::unordered_map<String, ASTPtr> column_to_updated;
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/// Contains columns that are changed by this stage,
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/// columns changed by the previous stages and also columns needed by the next stages.
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NameSet output_columns;
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std::unique_ptr<ExpressionAnalyzer> analyzer;
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/// A chain of actions needed to execute this stage.
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/// First steps calculate filter columns for DELETEs (in the same order as in `filter_column_names`),
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/// then there is (possibly) an UPDATE step, and finally a projection step.
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ExpressionActionsChain expressions_chain;
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Names filter_column_names;
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};
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std::unique_ptr<Block> updated_header;
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std::vector<Stage> stages;
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bool is_prepared = false; /// Has the sequence of stages been prepared.
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};
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}
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