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MDEV-20109: Optimizer ignores distinct key created for materialized...

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(Backported to 10.3, addressed review input)

Sj_materialization_picker::check_qep(): fix error in cost/fanout
calculations:
- for each join prefix, add #prefix_rows / TIME_FOR_COMPARE to the cost,
  like best_extension_by_limited_search does
- Remove the fanout produced by the subquery tables.
- Also take into account join condition selectivity

optimize_wo_join_buffering() (used by LooseScan and FirstMatch)
- also add #prefix_rows / TIME_FOR_COMPARE to the cost of each prefix.
- Also take into account join condition selectivity
This commit is contained in:
Sergei Petrunia
2019-08-29 15:37:49 +03:00
parent d58437d195
commit ef76f81c98
27 changed files with 392 additions and 295 deletions
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15
sql/sql_select.cc
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@ -8244,6 +8244,7 @@ void JOIN::get_prefix_cost_and_fanout(uint n_tables,
record_count= COST_MULT(record_count, best_positions[i].records_read);
read_time= COST_ADD(read_time, best_positions[i].read_time);
}
/* TODO: Take into account condition selectivities here */
}
*read_time_arg= read_time;// + record_count / TIME_FOR_COMPARE;
*record_count_arg= record_count;
@ -15975,10 +15976,20 @@ void optimize_wo_join_buffering(JOIN *join, uint first_tab, uint last_tab,
reopt_remaining_tables &= ~rs->table->map;
rec_count= COST_MULT(rec_count, pos.records_read);
cost= COST_ADD(cost, pos.read_time);
cost= COST_ADD(cost, rec_count / (double) TIME_FOR_COMPARE);
//TODO: take into account join condition selectivity here
double pushdown_cond_selectivity= 1.0;
table_map real_table_bit= rs->table->map;
if (join->thd->variables.optimizer_use_condition_selectivity > 1)
{
pushdown_cond_selectivity= table_cond_selectivity(join, i, rs,
reopt_remaining_tables &
~real_table_bit);
}
(*outer_rec_count) *= pushdown_cond_selectivity;
if (!rs->emb_sj_nest)
*outer_rec_count= COST_MULT(*outer_rec_count, pos.records_read);
}
join->cur_sj_inner_tables= save_cur_sj_inner_tables;