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MDEV-26301: Split optimization refills: Optimizer Trace coverage

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Add Optimizer Trace printouts.
This commit is contained in:
Sergei Petrunia
2023-05-03 13:49:32 +03:00
committed by Oleksandr Byelkin
parent ce7ffe61d8
commit ed3e6f66a2
4 changed files with 245 additions and 13 deletions
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72
sql/opt_split.cc
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@@ -228,6 +228,7 @@
#include "mariadb.h"
#include "sql_select.h"
#include "opt_trace.h"
/* Info on a splitting field */
struct SplM_field_info
@@ -387,6 +388,9 @@ bool JOIN::check_for_splittable_materialized()
if (!partition_list)
return false;
Json_writer_object trace_wrapper(thd);
Json_writer_object trace_split(thd, "check_split_materialized");
ORDER *ord;
Dynamic_array<SplM_field_ext_info> candidates;
@@ -432,7 +436,10 @@ bool JOIN::check_for_splittable_materialized()
}
}
if (candidates.elements() == 0) // no candidates satisfying (8.1) && (8.2)
{
trace_split.add("not_applicable", "group list has no candidates");
return false;
}
/*
For each table from this join find the keys that can be used for ref access
@@ -491,7 +498,11 @@ bool JOIN::check_for_splittable_materialized()
}
if (!spl_field_cnt) // No candidate field can be accessed by ref => !(9)
{
trace_split.add("not_applicable",
"no candidate field can be accessed through ref");
return false;
}
/*
Create a structure of the type SplM_opt_info and fill it with
@@ -509,16 +520,22 @@ bool JOIN::check_for_splittable_materialized()
spl_opt_info->tables_usable_for_splitting= 0;
spl_opt_info->spl_field_cnt= spl_field_cnt;
spl_opt_info->spl_fields= spl_field;
for (cand= cand_start; cand < cand_end; cand++)
{
if (!cand->is_usable_for_ref_access)
continue;
spl_field->producing_item= cand->producing_item;
spl_field->underlying_field= cand->underlying_field;
spl_field->mat_field= cand->mat_field;
spl_opt_info->tables_usable_for_splitting|=
cand->underlying_field->table->map;
spl_field++;
Json_writer_array trace_range(thd, "split_candidates");
for (cand= cand_start; cand < cand_end; cand++)
{
if (!cand->is_usable_for_ref_access)
continue;
trace_range.add(cand->producing_item);
spl_field->producing_item= cand->producing_item;
spl_field->underlying_field= cand->underlying_field;
spl_field->mat_field= cand->mat_field;
spl_opt_info->tables_usable_for_splitting|=
cand->underlying_field->table->map;
spl_field++;
}
}
/* Attach this info to the table T */
@@ -773,7 +790,7 @@ void JOIN::add_keyuses_for_splitting()
bzero((char*) &keyuse_ext_end, sizeof(keyuse_ext_end));
if (ext_keyuses_for_splitting->push(keyuse_ext_end))
goto err;
// psergey-todo: trace anything here?
spl_opt_info->unsplit_card= join_record_count;
rec_len= table->s->rec_buff_length;
@@ -946,7 +963,8 @@ SplM_plan_info * JOIN_TAB::choose_best_splitting(uint idx,
uint best_key= 0;
uint best_key_parts= 0;
table_map best_param_tables;
Json_writer_object trace_obj(thd, "choose_best_splitting");
Json_writer_array trace_arr(thd, "considered_keys");
/*
Check whether there are keys that can be used to join T employing splitting
and if so, select the best out of such keys
@@ -999,6 +1017,13 @@ SplM_plan_info * JOIN_TAB::choose_best_splitting(uint idx,
best_rec_per_key= rec_per_key;
best_key_keyuse_ext_start= key_keyuse_ext_start;
best_param_tables= needed_in_prefix;
// trace table, key_name, parts, needed_tables.
Json_writer_object cur_index(thd);
cur_index.
add("table_name", best_table->alias.ptr()).
add("index", best_table->key_info[best_key].name).
add("rec_per_key", best_rec_per_key).
add("param_tables", best_param_tables);
}
keyuse_ext++;
}
@@ -1006,6 +1031,8 @@ SplM_plan_info * JOIN_TAB::choose_best_splitting(uint idx,
}
while (keyuse_ext->table == table);
}
trace_arr.end();
spl_opt_info->last_plan= 0;
double refills= DBL_MAX;
table_map excluded_tables= remaining_tables | this->join->sjm_lookup_tables;
@@ -1031,6 +1058,10 @@ SplM_plan_info * JOIN_TAB::choose_best_splitting(uint idx,
break;
}
}
trace_obj.add("refills", refills).
add("spl_pd_boundary", *spl_pd_boundary);
/*
The key for splitting was chosen, look for the plan for this key
in the cache
@@ -1042,11 +1073,13 @@ SplM_plan_info * JOIN_TAB::choose_best_splitting(uint idx,
The plan for the chosen key has not been found in the cache.
Build a new plan and save info on it in the cache
*/
Json_writer_array wrapper(thd, "split_plan_search");
table_map all_table_map= (((table_map) 1) << join->table_count) - 1;
reset_validity_vars_for_keyuses(best_key_keyuse_ext_start, best_table,
best_key, excluded_tables, true);
choose_plan(join, all_table_map & ~join->const_table_map);
wrapper.end();
/*
Check that the chosen plan is really a splitting plan.
If not or if there is not enough memory to save the plan in the cache
@@ -1064,6 +1097,7 @@ SplM_plan_info * JOIN_TAB::choose_best_splitting(uint idx,
{
reset_validity_vars_for_keyuses(best_key_keyuse_ext_start, best_table,
best_key, excluded_tables, false);
trace_obj.add("split_plan_discarded", "constructed unapplicable query plan");
return 0;
}
@@ -1089,9 +1123,20 @@ SplM_plan_info * JOIN_TAB::choose_best_splitting(uint idx,
reset_validity_vars_for_keyuses(best_key_keyuse_ext_start, best_table,
best_key, excluded_tables, false);
}
else
trace_obj.add("cached_plan_found", 1);
if (spl_plan)
{
trace_obj.
add("lead_table", spl_plan->table->alias.ptr()).
add("index", spl_plan->table->key_info[spl_plan->key].name).
add("parts", spl_plan->parts).
add("split_sel", spl_plan->split_sel).
add("cost", spl_plan->cost).
add("records", (ha_rows) (records * spl_plan->split_sel)).
add("refills", refills);
if (refills * spl_plan->cost < spl_opt_info->unsplit_cost)
{
/*
@@ -1100,7 +1145,10 @@ SplM_plan_info * JOIN_TAB::choose_best_splitting(uint idx,
*/
spl_opt_info->last_plan= spl_plan;
spl_opt_info->last_refills= refills;
trace_obj.add("chosen", true);
}
else
trace_obj.add("chosen", false);
}
}
@@ -1132,7 +1180,7 @@ SplM_plan_info * JOIN_TAB::choose_best_splitting(uint idx,
@details
This function injects equalities pushed into a derived table T for which
the split optimization has been chosen by the optimizer. The function
is called by JOIN::inject_splitting_cond_for_all_tables_with_split_op().
is called by JOIN::inject_splitting_cond_for_all_tables_with_split_opt().
All equalities usable for splitting T whose right parts do not depend on
any of the 'excluded_tables' can be pushed into the where clause of the
derived table T.