Method execute

sql/sql_prepare.cc:5223–5493

*/

bool Prepared_statement::execute(String *expanded_query, bool open_cursor,
                                 select_result *result_arg,
                                 Server_side_cursor **cursor_arg)
{
  DBUG_ASSERT(result_arg);
  DBUG_ASSERT(cursor_arg);
  Statement stmt_backup;
  Query_arena *old_stmt_arena;
  bool error= TRUE;
  bool qc_executed= FALSE;
  char saved_db_buf[SAFE_NAME_LEN+1];
  LEX_STRING saved_db= { saved_db_buf, sizeof(saved_db_buf) };
  bool cur_db_changed;
  LEX_CSTRING stmt_db_name= db;

  if (check_charset_collation_map_version(thd, thd->m_reprepare_observer))
    return true;

  status_var_increment(thd->status_var.com_stmt_execute);

  if (flags & (uint) IS_IN_USE)
  {
    my_error(ER_PS_NO_RECURSION, MYF(0));
    return TRUE;
  }

  /*
    For SHOW VARIABLES lex->result is NULL, as it's a non-SELECT
    command. For such queries we don't return an error and don't
    open a cursor -- the client library will recognize this case and
    materialize the result set.
    For SELECT statements lex->result is created in
    check_prepared_statement. lex->result->simple_select() is FALSE
    in INSERT ... SELECT and similar commands.
  */

  if (open_cursor && lex->result && lex->result->check_simple_select())
  {
    DBUG_PRINT("info",("Cursor asked for not SELECT stmt"));
    return TRUE;
  }

  /* In case the command has a call to SP which re-uses this statement name */
  flags|= IS_IN_USE;

  close_cursor();

  /*
    If the free_list is not empty, we'll wrongly free some externally
    allocated items when cleaning up after execution of this statement.
  */
  DBUG_ASSERT(thd->Item_change_list::is_empty());

  /* 
   The only case where we should have items in the thd->free_list is
   after stmt->set_params_from_vars(), which may in some cases create
   Item_null objects.
  */