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116 lines
3.9 KiB
C++
116 lines
3.9 KiB
C++
#pragma once
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#include <Core/Block.h>
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#include <Core/NamesAndTypes.h>
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#include <Interpreters/Aliases.h>
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#include <Interpreters/SelectQueryOptions.h>
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#include <Interpreters/DatabaseAndTableWithAlias.h>
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#include <Storages/IStorage_fwd.h>
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namespace DB
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{
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class ASTFunction;
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struct ASTTablesInSelectQueryElement;
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class TableJoin;
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class Context;
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struct Settings;
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struct SelectQueryOptions;
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using Scalars = std::map<String, Block>;
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struct StorageInMemoryMetadata;
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using StorageMetadataPtr = std::shared_ptr<const StorageInMemoryMetadata>;
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struct TreeRewriterResult
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{
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ConstStoragePtr storage;
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StorageMetadataPtr metadata_snapshot;
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std::shared_ptr<TableJoin> analyzed_join;
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const ASTTablesInSelectQueryElement * ast_join = nullptr;
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NamesAndTypesList source_columns;
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NameSet source_columns_set; /// Set of names of source_columns.
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/// Set of columns that are enough to read from the table to evaluate the expression. It does not include joined columns.
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NamesAndTypesList required_source_columns;
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Aliases aliases;
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std::vector<const ASTFunction *> aggregates;
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/// Which column is needed to be ARRAY-JOIN'ed to get the specified.
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/// For example, for `SELECT s.v ... ARRAY JOIN a AS s` will get "s.v" -> "a.v".
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NameToNameMap array_join_result_to_source;
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/// For the ARRAY JOIN section, mapping from the alias to the full column name.
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/// For example, for `ARRAY JOIN [1,2] AS b` "b" -> "array(1,2)" will enter here.
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/// Note: not used further.
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NameToNameMap array_join_alias_to_name;
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/// The backward mapping for array_join_alias_to_name.
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/// Note: not used further.
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NameToNameMap array_join_name_to_alias;
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/// Predicate optimizer overrides the sub queries
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bool rewrite_subqueries = false;
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bool optimize_trivial_count = false;
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/// Cache isRemote() call for storage, because it may be too heavy.
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bool is_remote_storage = false;
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/// Results of scalar sub queries
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Scalars scalars;
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TreeRewriterResult(
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const NamesAndTypesList & source_columns_,
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ConstStoragePtr storage_ = {},
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const StorageMetadataPtr & metadata_snapshot_ = {},
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bool add_special = true);
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void collectSourceColumns(bool add_special);
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void collectUsedColumns(const ASTPtr & query, bool is_select);
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Names requiredSourceColumns() const { return required_source_columns.getNames(); }
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const Scalars & getScalars() const { return scalars; }
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};
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using TreeRewriterResultPtr = std::shared_ptr<const TreeRewriterResult>;
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/// Tree Rewriter in terms of CMU slides @sa https://15721.courses.cs.cmu.edu/spring2020/slides/19-optimizer1.pdf
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///
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/// Optimises AST tree and collect information for further expression analysis in ExpressionAnalyzer.
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/// Result AST has the following invariants:
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/// * all aliases are substituted
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/// * qualified names are translated
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/// * scalar subqueries are executed replaced with constants
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/// * unneeded columns are removed from SELECT clause
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/// * duplicated columns are removed from ORDER BY, LIMIT BY, USING(...).
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class TreeRewriter
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{
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public:
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TreeRewriter(const Context & context_)
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: context(context_)
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{}
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/// Analyze and rewrite not select query
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TreeRewriterResultPtr analyze(
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ASTPtr & query,
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const NamesAndTypesList & source_columns_,
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ConstStoragePtr storage = {},
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const StorageMetadataPtr & metadata_snapshot = {},
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bool allow_aggregations = false) const;
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/// Analyze and rewrite select query
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TreeRewriterResultPtr analyzeSelect(
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ASTPtr & query,
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TreeRewriterResult && result,
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const SelectQueryOptions & select_options = {},
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const std::vector<TableWithColumnNamesAndTypes> & tables_with_columns = {},
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const Names & required_result_columns = {},
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std::shared_ptr<TableJoin> table_join = {}) const;
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private:
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const Context & context;
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static void normalize(ASTPtr & query, Aliases & aliases, const Settings & settings);
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};
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}
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