text: #pragma once
  
  #include <Core/Names.h>
  #include <Core/Types.h>
  #include <Core/NamesAndTypes.h>
  #include <Parsers/IAST_fwd.h>
  
  #include <memory>
  #include <optional>
  
  
  namespace DB
  {
  
  class ASTSelectQuery;
  class ASTIdentifier;
  struct ASTTableExpression;
  class Context;
  
  
  /// Extracts database name (and/or alias) from table expression or identifier
  struct DatabaseAndTableWithAlias
  {
      String database;
      String table;
      String alias;
  
      DatabaseAndTableWithAlias() = default;
      DatabaseAndTableWithAlias(const ASTPtr & identifier_node, const String & current_database = "");
      DatabaseAndTableWithAlias(const ASTIdentifier & identifier, const String & current_database = "");
      DatabaseAndTableWithAlias(const ASTTableExpression & table_expression, const String & current_database = "");
  
      /// "alias." or "table." if alias is empty
      String getQualifiedNamePrefix(bool with_dot = true) const;
  
      /// Check if it satisfies another db_table name. @note opterion is not symmetric.
      bool satisfies(const DatabaseAndTableWithAlias & table, bool table_may_be_an_alias);
  };
  
  struct TableWithColumnNames
  {
      DatabaseAndTableWithAlias table;
      Names columns;
      Names hidden_columns;
  
      TableWithColumnNames(const DatabaseAndTableWithAlias & table_, const Names & columns_)
          : table(table_)
          , columns(columns_)
      {}
  
      void addHiddenColumns(const NamesAndTypesList & addition)
      {
          for (auto & column : addition)
              hidden_columns.push_back(column.name);
      }
  
      bool hasColumn(const String & name) const
      {
          if (columns_set.empty())
          {
              columns_set.insert(columns.begin(), columns.end());
              columns_set.insert(hidden_columns.begin(), hidden_columns.end());
          }
  
          return columns_set.count(name);
      }
  
  private:
      mutable NameSet columns_set;
  };
  
  std::vector<DatabaseAndTableWithAlias> getDatabaseAndTables(const ASTSelectQuery & select_query, const String & current_database);
  std::optional<DatabaseAndTableWithAlias> getDatabaseAndTable(const ASTSelectQuery & select, size_t table_number);
  
  }
  