Method execute

sql/sql_select.cc:34945–35025

*/

bool Sql_cmd_dml::execute(THD *thd)
{
  lex = thd->lex;
  ha_rows found= 0, changed= 0;
  bool res;

  SELECT_LEX_UNIT *unit = &lex->unit;
  SELECT_LEX *select_lex= lex->first_select_lex();


  if (!is_prepared())
  {
    /*
      This is called when processing
      - a DML statement
      - PREPARE stmt FROM <DML "statement>"
      - EXECUTE stmt when stmt is prepared from a DML statement.
      The call will invoke  open_tables_for_query()
    */
    if (prepare(thd))
       goto err;
  }
  else // This branch currently is never used for DML commands
  {
    if (precheck(thd))
      goto err;

    MYSQL_DML_START(thd);

    if (open_tables_for_query(thd, lex->query_tables, &table_count, 0,
                              get_dml_prelocking_strategy()))
      goto err;
  }

  THD_STAGE_INFO(thd, stage_init);

  /*
    Locking of tables is done after preparation but before optimization.
    This allows to do better partition pruning and avoid locking unused
    partitions. As a consequence, in such a case, prepare stage can rely only
    on metadata about tables used and not data from them.
  */
  if (!is_empty_query())
  {
    if (lock_tables(thd, lex->query_tables, table_count, 0))
      goto err;
  }

  unit->set_limit(select_lex);

  /* Perform statement-specific execution */
  res = execute_inner(thd);

  if (res)
    goto err;
  else
    MYSQL_DML_GET_STAT(thd, found, changed);