ClickHouse/dbms/src/Interpreters/AnalyzedJoin.h

#pragma once

#include <Core/Names.h>
#include <Core/NamesAndTypes.h>
#include <Core/SettingsCommon.h>
#include <Parsers/ASTTablesInSelectQuery.h>

#include <utility>
#include <memory>

namespace DB
{

class Context;
class ASTSelectQuery;
struct DatabaseAndTableWithAlias;
class Block;

class Join;
using JoinPtr = std::shared_ptr<Join>;

struct AnalyzedJoin
{
    /** Query of the form `SELECT expr(x) AS k FROM t1 ANY LEFT JOIN (SELECT expr(x) AS k FROM t2) USING k`
      * The join is made by column k.
      * During the JOIN,
      *  - in the "right" table, it will be available by alias `k`, since `Project` action for the subquery was executed.
      *  - in the "left" table, it will be accessible by the name `expr(x)`, since `Project` action has not been executed yet.
      * You must remember both of these options.
      *
      * Query of the form `SELECT ... from t1 ANY LEFT JOIN (SELECT ... from t2) ON expr(t1 columns) = expr(t2 columns)`
      *     to the subquery will be added expression `expr(t2 columns)`.
      * It's possible to use name `expr(t2 columns)`.
      */

private:
    friend class SyntaxAnalyzer;

    Names key_names_left;
    Names key_names_right; /// Duplicating names are qualified.
    ASTs key_asts_left;
    ASTs key_asts_right;
    ASTTableJoin table_join;
    bool join_use_nulls = false;

    /// All columns which can be read from joined table. Duplicating names are qualified.
    NamesAndTypesList columns_from_joined_table;
    /// Columns will be added to block by JOIN. It's a subset of columns_from_joined_table with corrected Nullability
    NamesAndTypesList columns_added_by_join;

    /// Name -> original name. Names are the same as in columns_from_joined_table list.
    std::unordered_map<String, String> original_names;
    /// Original name -> name. Only ranamed columns.
    std::unordered_map<String, String> renames;

public:
    void addUsingKey(const ASTPtr & ast);
    void addOnKeys(ASTPtr & left_table_ast, ASTPtr & right_table_ast);

    bool hasUsing() const { return table_join.using_expression_list != nullptr; }
    bool hasOn() const { return !hasUsing(); }

    NameSet getQualifiedColumnsSet() const;
    NameSet getOriginalColumnsSet() const;
    std::unordered_map<String, String> getOriginalColumnsMap(const NameSet & required_columns) const;

    void deduplicateAndQualifyColumnNames(const NameSet & left_table_columns, const String & right_table_prefix);
    size_t rightKeyInclusion(const String & name) const;

    void appendRequiredColumns(const Block & sample, NameSet & required_columns) const;
    void addJoinedColumn(const NameAndTypePair & joined_column);
    void addJoinedColumnsAndCorrectNullability(Block & sample_block) const;

    ASTPtr leftKeysList() const;
    ASTPtr rightKeysList() const; /// For ON syntax only

    Names requiredJoinedNames() const;
    const Names & keyNamesLeft() const { return key_names_left; }
    const NamesAndTypesList & columnsFromJoinedTable() const { return columns_from_joined_table; }
    const NamesAndTypesList & columnsAddedByJoin() const { return columns_added_by_join; }

    JoinPtr makeHashJoin(const Block & sample_block, const SizeLimits & size_limits_for_join) const;

    static bool sameJoin(const AnalyzedJoin * x, const AnalyzedJoin * y);
};

struct ASTTableExpression;
NamesAndTypesList getNamesAndTypeListFromTableExpression(const ASTTableExpression & table_expression, const Context & context);

}