Hello,
1)
+ bool is_zero() const
+ {
+ if (io_cost || cpu_cost || import_cost || mem_cost)
+ return false;
+ return true;
return !(io_cost || cpu_cost || import_cost || mem_cost);
is simpler.
2) In definition of class, short comments like:
+ /**
+ Add to IO cost
+ */
could be shorter on one line:
/// Add to IO cost
3) While you're changing DsMrr_impl::choose_mrr_impl(), could you move
the declaration of "COST_VECT dsmrr_cost" down to right before the call
to get_disk_sweep_mrr_cost()?
4) Biggest question:
@@ -14105,7 +14107,8 @@ void Optimize_table_order::advance_sj_st
DBUG_ENTER("Optimize_table_order::advance_sj_state");
- pos->prefix_cost.convert_from_cost(*current_read_time);
+ DBUG_ASSERT(pos->prefix_cost.is_zero());
+ pos->prefix_cost.add_io(*current_read_time);
I'm not 100% sure that the assertion will never fire, as a POSITION
serves during evaluation of multiple candidate plans, without, IIUC, any
resetting in between; could a next pass find a non-zero cost left by a
previous pass? I suggest asking Roy to double check this.
Otherwise, ok to push.
--
Mr. Guilhem Bichot <guilhem.bichot@stripped>
Oracle / MySQL / Optimizer team, Lead Software Engineer
Bordeaux, France
www.oracle.com / www.mysql.com
