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MDEV-23677: Optimizer trace: remove "no predicate for first keypart" (not)

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Don't remove (reasons given in Jira), instead add test coverage.
Improve other printout in best_access_path.
This commit is contained in:
Sergei Petrunia 2021-03-18 21:04:33 +03:00
parent 4903031baa
commit 2b3fd5dff0
3 changed files with 73 additions and 7 deletions
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38
mysql-test/main/opt_trace.result
View File

@ -4010,6 +4010,7 @@ explain delete t0,t1 from t0, t1 where t0.a=t1.a and t1.a<3 {
{
"access_type": "ref",
"index": "a",
"rec_per_key_stats_missing": true,
"used_range_estimates": false,
"cause": "not better than ref estimates",
"rows": 2,
@ -8793,5 +8794,42 @@ json_detailed(json_extract(trace, '$**.in_to_subquery_conversion'))
]
set in_predicate_conversion_threshold=@tmp;
drop table t0;
#
# End of 10.5 tests
#
#
# MDEV-23677: Optimizer trace ... (test coverage)
#
create table t1(a int, b int, c int, primary key (a,b,c));
insert into t1 values (0,0,0),(1,1,1),(2,2,2),(3,3,3),(4,4,4);
create table t2 (a int, b int);
insert into t2 values (1,1),(2,2);
create table t3 (a int, b int, c int);
insert into t3 values (0,0,0),(1,1,1),(2,2,2),(3,3,3),(4,4,4);
explain select * from t2,t1,t3 where t2.b= t1.b and t1.a=t3.a;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 ALL NULL NULL NULL NULL 2 Using where
1 SIMPLE t3 ALL NULL NULL NULL NULL 5 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t1 ref PRIMARY PRIMARY 8 test.t3.a,test.t2.b 1 Using index
set @trace=(select trace from information_schema.optimizer_trace);
set @path= (select json_search(@trace, 'one', 'no predicate for first keypart'));
set @sub_path= substr(@path, 2, locate('.best_access_path', @path)-2);
select @sub_path;
@sub_path
$.steps[1].join_optimization.steps[4].considered_execution_plans[0].rest_of_plan[0]
select
json_detailed(json_extract(
@trace,
concat(@sub_path,'.best_access_path.considered_access_paths[0]')
)) as S;
S
{
"access_type": "ref",
"index": "PRIMARY",
"rows": 1.79769e308,
"cost": 1.79769e308,
"chosen": false,
"cause": "no predicate for first keypart"
}
drop table t1,t2,t3;
set optimizer_trace='enabled=off';

30
mysql-test/main/opt_trace.test
View File

@ -696,5 +696,35 @@ from information_schema.optimizer_trace;
set in_predicate_conversion_threshold=@tmp;
drop table t0;
--echo #
--echo # End of 10.5 tests
--echo #
--echo #
--echo # MDEV-23677: Optimizer trace ... (test coverage)
--echo #
create table t1(a int, b int, c int, primary key (a,b,c));
insert into t1 values (0,0,0),(1,1,1),(2,2,2),(3,3,3),(4,4,4);
create table t2 (a int, b int);
insert into t2 values (1,1),(2,2);
create table t3 (a int, b int, c int);
insert into t3 values (0,0,0),(1,1,1),(2,2,2),(3,3,3),(4,4,4);
explain select * from t2,t1,t3 where t2.b= t1.b and t1.a=t3.a;
set @trace=(select trace from information_schema.optimizer_trace);
set @path= (select json_search(@trace, 'one', 'no predicate for first keypart'));
set @sub_path= substr(@path, 2, locate('.best_access_path', @path)-2);
select @sub_path;
select
json_detailed(json_extract(
@trace,
concat(@sub_path,'.best_access_path.considered_access_paths[0]')
)) as S;
drop table t1,t2,t3;
set optimizer_trace='enabled=off';

12
sql/sql_select.cc
View File

@ -7637,6 +7637,7 @@ best_access_path(JOIN *join,
{
if (!(records= keyinfo->actual_rec_per_key(key_parts-1)))
{ /* Prefer longer keys */
trace_access_idx.add("rec_per_key_stats_missing", true);
records=
((double) s->records / (double) rec *
(1.0 +
@ -7663,7 +7664,7 @@ best_access_path(JOIN *join,
records > (double) table->opt_range[key].rows)
{
records= (double) table->opt_range[key].rows;
trace_access_idx.add("used_range_estimates", true);
trace_access_idx.add("used_range_estimates", "clipped down");
}
else
{
@ -7780,19 +7781,15 @@ best_access_path(JOIN *join,
if (!found_ref && // (1)
records < rows) // (3)
{
trace_access_idx.add("used_range_estimates", true);
trace_access_idx.add("used_range_estimates", "clipped up");
records= rows;
}
}
else /* (table->quick_key_parts[key] < max_key_part) */
{
trace_access_idx.add("chosen", true);
cause= "range uses less keyparts";
}
}
}
else
{
trace_access_idx.add("rec_per_key_stats_missing", true);
/*
Assume that the first key part matches 1% of the file
and that the whole key matches 10 (duplicates) or 1
@ -7856,6 +7853,7 @@ best_access_path(JOIN *join,
const_part)) &&
records > (double) table->opt_range[key].rows)
{
trace_access_idx.add("used_range_estimates", true);
records= (double) table->opt_range[key].rows;
}
}