Hi, Zardosht!
On Jan 12, Zardosht Kasheff wrote:
>
> Hello,
>
> I was wondering what the purpose of HTON_FLUSH_AFTER_RENAME is for
> handertons. It seems exposing this flag causes a call to "flush logs"
> after any "alter table". Is there any other purpose? The relevant code
> seems to be the following in sql_table.cc:
>
> if (ha_check_storage_engine_flag(old_db_type, HTON_FLUSH_AFTER_RENAME))
> {
> /*
> For the alter table to be properly flushed to the logs, we
> have to open the new table. If not, we get a problem on server
> shutdown. But we do not need to attach MERGE children.
> */
> char path[FN_REFLEN];
> TABLE *t_table;
> build_table_filename(path, sizeof(path), new_db, table_name, "", 0);
> t_table= open_temporary_table(thd, path, new_db, tmp_name, 0);
> if (t_table)
> {
> intern_close_table(t_table);
> my_free(t_table, MYF(0));
> }
> else
> sql_print_warning("Could not open table %s.%s after rename\n",
> new_db,table_name);
> ha_flush_logs(old_db_type);
> }
>
>
> I see the last line calls "flush logs". I do not understand what the
> code before that does.
The original 2002 code looked like this:
#ifdef HAVE_BERKELEY_DB
extern bool berkeley_flush_logs(void);
if (old_db_type == DB_TYPE_BERKELEY_DB)
{
(void)berkeley_flush_logs();
table=open_ltable(thd,table_list,TL_READ);
}
#endif
it's a workaround for some BDB quirk, and perhaps there could've been a
better fix anyway. Nobody but BDB ever needed that or used
HTON_FLUSH_AFTER_RENAME.
Feel free to ignore this flag :)
Regards,
Sergei
