sql_update.h

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#ifndef SQL_UPDATE_INCLUDED
#define SQL_UPDATE_INCLUDED

#include <sys/types.h>

#include "mem_root_deque.h"
#include "my_alloc.h"
#include "my_sqlcommand.h"
#include "my_table_map.h"
#include "sql/query_result.h"  // Query_result_interceptor
#include "sql/sql_cmd_dml.h"   // Sql_cmd_dml
#include "sql/sql_list.h"
#include "sql/thr_malloc.h"

class COPY_INFO;
class Copy_field;
class Item;
class JOIN;
class Query_block;
class Query_expression;
class RowIterator;
class Select_lex_visitor;
class THD;
class Temp_table_param;
struct TABLE;
class Table_ref;

bool records_are_comparable(const TABLE *table);
bool compare_records(const TABLE *table);
bool should_switch_to_multi_table_if_subqueries(const THD *thd,
                                                const Query_block *select,
                                                const Table_ref *table_list);

class Query_result_update final : public Query_result_interceptor {
  /// Number of tables being updated
  uint update_table_count{0};
  /// Pointer to list of updated tables, linked via 'next_local'
  Table_ref *update_tables{nullptr};
  /// Array of references to temporary tables used to store cached updates
  TABLE **tmp_tables{nullptr};
  /// Array of parameter structs for creation of temporary tables
  Temp_table_param *tmp_table_param{nullptr};
  /// The first table in the join operation
  TABLE *main_table{nullptr};
  /**
    In a multi-table update, this is equal to the first table in the join
    operation (#main_table) if that table can be updated on the fly while
    scanning it. It is `nullptr` otherwise.

    @see safe_update_on_fly
  */
  TABLE *table_to_update{nullptr};
  /// List of pointers to fields to update, in order from statement
  const mem_root_deque<Item *> *fields;
  /// List of pointers to values to update with, in order from statement
  const mem_root_deque<Item *> *values;
  /// The fields list decomposed into separate lists per table
  mem_root_deque<Item *> **fields_for_table;
  /// The values list decomposed into separate lists per table
  mem_root_deque<Item *> **values_for_table;
  /**
   List of tables referenced in the CHECK OPTION condition of
   the updated view excluding the updated table.
  */
  List<TABLE> unupdated_check_opt_tables;
  /// ???
  Copy_field *copy_field{nullptr};

  /**
     Array of update operations, arranged per _updated_ table. For each
     _updated_ table in the multiple table update statement, a COPY_INFO
     pointer is present at the table's position in this array.

     The array is allocated and populated during Query_result_update::prepare().
     The position that each table is assigned is also given here and is stored
     in the member TABLE::pos_in_table_list::shared. However, this is a publicly
     available field, so nothing can be trusted about its integrity.

     This member is NULL when the Query_result_update is created.

     @see Query_result_update::prepare
  */
  COPY_INFO **update_operations{nullptr};

 public:
  Query_result_update(mem_root_deque<Item *> *field_list,
                      mem_root_deque<Item *> *value_list)
      : Query_result_interceptor(), fields(field_list), values(value_list) {}
  bool need_explain_interceptor() const override { return true; }
  bool prepare(THD *thd, const mem_root_deque<Item *> &list,
               Query_expression *u) override;
  bool optimize();
  bool start_execution(THD *thd) override;
  bool send_data(THD *thd, const mem_root_deque<Item *> &items) override;
  bool do_updates(THD *thd);
  bool send_eof(THD *thd) override;
  void cleanup() override;
  unique_ptr_destroy_only<RowIterator> create_iterator(
      THD *thd, MEM_ROOT *mem_root,
      unique_ptr_destroy_only<RowIterator> source);
};

class Sql_cmd_update final : public Sql_cmd_dml {
 public:
  Sql_cmd_update(bool multitable_arg, mem_root_deque<Item *> *update_values)
      : multitable(multitable_arg),
        original_fields(*THR_MALLOC),
        update_value_list(update_values) {}

  enum_sql_command sql_command_code() const override {
    return multitable ? SQLCOM_UPDATE_MULTI : SQLCOM_UPDATE;
  }

  bool is_single_table_plan() const override { return !multitable; }

 protected:
  bool precheck(THD *thd) override;
  bool check_privileges(THD *thd) override;

  bool prepare_inner(THD *thd) override;

  bool execute_inner(THD *thd) override;

 private:
  bool update_single_table(THD *thd);

  bool multitable;

  /// Bitmap of all tables which are to be updated
  table_map tables_for_update{0};

  bool accept(THD *thd, Select_lex_visitor *visitor) override;

  /// Convert list of fields to update to base table fields
  bool make_base_table_fields(THD *thd, mem_root_deque<Item *> *items);

 public:
  /// The original list of fields to update, used for privilege checking
  mem_root_deque<Item *> original_fields;
  /// The values used to update fields
  mem_root_deque<Item *> *update_value_list;
};

/// Find out which of the target tables can be updated immediately while
/// scanning. This is used by the old optimizer *after* the plan has been
/// created. The hypergraph optimizer does not use this function, as it makes
/// the decision about immediate update *during* planning, not after planning.
///
/// @param join The top-level JOIN object of the UPDATE statement.
/// @param single_target True if the UPDATE statement has exactly
///                      one target table.
/// @return Map of tables to update while scanning.
table_map GetImmediateUpdateTable(const JOIN *join, bool single_target);

/// Makes the TABLE and handler objects ready for being used in an UPDATE
/// statement. Called at the beginning of each execution.
///
/// @param join  The top-level JOIN object of the UPDATE operation.
/// @return true on error.
bool FinalizeOptimizationForUpdate(JOIN *join);

/// Creates an UpdateRowsIterator which updates the rows returned by the given
/// "source" iterator.
unique_ptr_destroy_only<RowIterator> CreateUpdateRowsIterator(
    THD *thd, MEM_ROOT *mem_root, JOIN *join,
    unique_ptr_destroy_only<RowIterator> source);

#endif /* SQL_UPDATE_INCLUDED */