TableParseJoin.h

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// # TableParseJoin.h: Class handling the join clause
// # Copyright (C) 2022
// # Associated Universities, Inc. Washington DC, USA.
// #
// # This library is free software; you can redistribute it and/or modify it
// # under the terms of the GNU Library General Public License as published by
// # the Free Software Foundation; either version 2 of the License, or (at your
// # option) any later version.
// #
// # This library is distributed in the hope that it will be useful, but WITHOUT
// # ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
// # FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library General Public
// # License for more details.
// #
// # You should have received a copy of the GNU Library General Public License
// # along with this library; if not, write to the Free Software Foundation,
// # Inc., 675 Massachusetts Ave, Cambridge, MA 02139, USA.
// #
// # Correspondence concerning AIPS++ should be addressed as follows:
// #        Internet email: casa-feedback@nrao.edu.
// #        Postal address: AIPS++ Project Office
// #                        National Radio Astronomy Observatory
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#ifndef TABLES_TABLEPARSEJOIN_H
#define TABLES_TABLEPARSEJOIN_H
 
// # Includes
#include <casacore/casa/aips.h>
#include <casacore/tables/TaQL/ExprNodeRep.h>
#include <casacore/tables/TaQL/TaQLJoin.h>
#include <vector>
 
namespace casacore {  // # NAMESPACE CASACORE - BEGIN
 
// # Forward declarations.
class TableParse;
class TableParseQuery;
class TableExprNode;
class Table;
 
// <summary>
// Class handling a join clause in a TaQL command
// </summary>
 
// <use visibility=local>
 
// <reviewed reviewer="Tammo Jan Dijkema" date="2022/12/15" tests="tTableGramJoin">
// </reviewed>
 
// <synopsis>
// TableParseQuery holds a vector of TableParseJoin objects, one for each
// join clause in a TaQL command.
// <br>TableParseJoin holds the join condition expression and the from and
// join tables involved in the expression. The from tables are all tables in
// the TaQL command prior to this join clause. The join tables are the tables
// mentioned in the join clause.
// TableParseJoin also tells if the join is nested in another join by keeping
// the index of the parent TableParseJoin object in the vector in TableParseQuery.
//
// The ON condition expression is split in its AND parts; basically each part
// involves a column comparison. Each part must contain an = for an exact match
// or IN comparison for matching an interval.
// A tree, consisting of TaQLJoinBase objects, is built to execute the condition.
// It finds the matching row in the join table given a row in the main table.
// Each level in the tree is an AND part in the condition.
// </synopsis>
 
class TableParseJoin {
 public:
  explicit TableParseJoin(TableParseQuery*);
 
  // Add a join table nr, name, or object to the container.
  void addTable(Int tabnr, const String& name, const Table& table, const String& shorthand,
                const std::vector<const Table*>& tempTables,
                const std::vector<TableParseQuery*>& stack);
 
  // Handle the ON condition of a join.
  void handleCondition(const TableExprNode& expr);
 
  // Find the row in the join table for the given main table row.
  // # In the initialization phase of TaQLJoin, the itsJoin pointer
  // # is not set. In that case the given row id is already the original
  // # rownr in the join table and should be returned as such.
  Int64 findRow(const TableExprId& id) const;
 
 private:
  // Split the ON condition recursively into its AND parts.
  void splitAnd(const TENShPtr& node, std::vector<TENShPtr>& parts);
 
  // Handle all AND parts of the join condition.
  void handleConditionParts(std::vector<TENShPtr>& parts);
 
  // Tell how many tables in the exprTables vector are the same as those
  // in the tables vector.
  uInt findMatchingTables(const std::vector<Table>& exprTables,
                          const std::vector<Table>& tables) const;
 
  // Check if all join tables in the vector have the same number of rows.
  rownr_t checkNrow(const std::vector<Table>&) const;
 
  // Add the tables in the other vector to the tables vector.
  // Only do that for tables not occurring in the tables vector yet.
  void addUniqueTables(std::vector<Table>& tables, const std::vector<Table>& other);
 
  // # Data members.
  TableParseQuery* itsParent;
  std::vector<Table> itsFromTables;
  std::vector<Table> itsJoinTables;
  // # Index in TableParseQuery's vector of joins; <0 is no parent join.
  Int itsParentJoinIndex;
  std::shared_ptr<TaQLJoinBase> itsJoin;
  mutable Int64 itsLastMainRow;  // Last main table row looked for
  mutable Int64 itsLastJoinRow;  // Join table row matching itsLastMainRow
};
 
}  // namespace casacore
 
#endif