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83 lines
2.9 KiB
C++
83 lines
2.9 KiB
C++
#pragma once
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#include <Core/Names.h>
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#include <Core/NamesAndTypes.h>
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#include <Parsers/IAST.h>
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#include <utility>
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#include <memory>
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namespace DB
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{
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class Context;
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class ASTSelectQuery;
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struct DatabaseAndTableWithAlias;
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class ExpressionActions;
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using ExpressionActionsPtr = std::shared_ptr<ExpressionActions>;
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struct JoinedColumn
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{
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/// Column will be joined to block.
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NameAndTypePair name_and_type;
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/// original column name from joined source.
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String original_name;
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JoinedColumn(NameAndTypePair name_and_type_, String original_name_)
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: name_and_type(std::move(name_and_type_)), original_name(std::move(original_name_)) {}
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bool operator==(const JoinedColumn & o) const
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{
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return name_and_type == o.name_and_type && original_name == o.original_name;
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}
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};
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using JoinedColumnsList = std::list<JoinedColumn>;
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struct AnalyzedJoin
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{
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/// NOTE: So far, only one JOIN per query is supported.
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/** Query of the form `SELECT expr(x) AS k FROM t1 ANY LEFT JOIN (SELECT expr(x) AS k FROM t2) USING k`
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* The join is made by column k.
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* During the JOIN,
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* - in the "right" table, it will be available by alias `k`, since `Project` action for the subquery was executed.
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* - in the "left" table, it will be accessible by the name `expr(x)`, since `Project` action has not been executed yet.
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* You must remember both of these options.
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*
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* Query of the form `SELECT ... from t1 ANY LEFT JOIN (SELECT ... from t2) ON expr(t1 columns) = expr(t2 columns)`
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* to the subquery will be added expression `expr(t2 columns)`.
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* It's possible to use name `expr(t2 columns)`.
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*/
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Names key_names_left;
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Names key_names_right; /// Duplicating names are qualified.
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ASTs key_asts_left;
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ASTs key_asts_right;
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/// All columns which can be read from joined table. Duplicating names are qualified.
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JoinedColumnsList columns_from_joined_table;
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/// Columns from joined table which may be added to block.
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/// It's columns_from_joined_table without duplicate columns and possibly modified types.
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JoinedColumnsList available_joined_columns;
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void addUsingKey(const ASTPtr & ast);
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void addOnKeys(ASTPtr & left_table_ast, ASTPtr & right_table_ast);
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ExpressionActionsPtr createJoinedBlockActions(
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const JoinedColumnsList & columns_added_by_join, /// Subset of available_joined_columns.
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const ASTSelectQuery * select_query_with_join,
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const Context & context) const;
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Names getOriginalColumnNames(const NameSet & required_columns) const;
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void calculateColumnsFromJoinedTable(const NamesAndTypesList & columns, const Names & original_names);
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void calculateAvailableJoinedColumns(bool make_nullable);
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};
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struct ASTTableExpression;
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NamesAndTypesList getNamesAndTypeListFromTableExpression(const ASTTableExpression & table_expression, const Context & context);
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}
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