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c630e23a18
(Variant 4, with @@optimizer_adjust_secondary_key_costs, reuse in two places, and conditions are replaced with equivalent simpler forms in two more) In best_access_path(), ReuseRangeEstimateForRef-3, the check for whether "all used key_part_i used key_part_i=const" was incorrect: it may produced a "NO" answer for cases when we had: key_part1= const // some key parts are usable key_part2= value_not_in_join_prefix //present but unusable key_part3= non_const_value // unusable due to gap in key parts. This caused the optimizer to fail to apply ReuseRangeEstimateForRef heuristics. The consequence is poor query plan choice when the index in question has very skewed data distribution. The fix is enabled if its @@optimizer_adjust_secondary_key_costs flag is set.
241 lines
9.8 KiB
Text
241 lines
9.8 KiB
Text
create table t1 (
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pk int primary key auto_increment,
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nm varchar(32),
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fl1 tinyint default 0,
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fl2 tinyint default 0,
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index idx1(nm, fl1),
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index idx2(fl2)
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) engine=myisam;
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create table name (
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pk int primary key auto_increment,
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nm bigint
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) engine=myisam;
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create table flag2 (
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pk int primary key auto_increment,
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fl2 tinyint
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) engine=myisam;
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insert into name(nm) select seq from seq_1_to_1000 order by rand(17);
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insert into flag2(fl2) select seq mod 2 from seq_1_to_1000 order by rand(19);
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insert into t1(nm,fl2)
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select nm, fl2 from name, flag2 where name.pk = flag2.pk;
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analyze table t1 persistent for all;
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Table Op Msg_type Msg_text
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test.t1 analyze status Engine-independent statistics collected
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test.t1 analyze status Table is already up to date
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set optimizer_trace="enabled=on";
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set optimizer_switch='rowid_filter=on';
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set statement optimizer_adjust_secondary_key_costs=0 for
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explain select * from t1 where nm like '500%' AND fl2 = 0;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 range idx1,idx2 idx1 35 NULL 1 Using index condition; Using where
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Warnings:
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Warning 1287 '@@optimizer_adjust_secondary_key_costs' is deprecated and will be removed in a future release
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Warning 1287 '@@optimizer_adjust_secondary_key_costs' is deprecated and will be removed in a future release
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set @trace=(select trace from information_schema.optimizer_trace);
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select json_detailed(json_extract(@trace, '$**.considered_access_paths'));
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json_detailed(json_extract(@trace, '$**.considered_access_paths'))
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[
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[
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{
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"access_type": "ref",
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"index": "idx2",
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"used_range_estimates": true,
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"filter":
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{
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"rowid_filter_index": "idx1",
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"index_only_cost": 0.045598762,
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"filter_startup_cost": 0.000899465,
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"find_key_and_filter_lookup_cost": 0.03086808,
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"filter_selectivity": 0.001,
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"original_rows": 492,
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"new_rows": 0.492,
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"original_access_cost": 0.59235049,
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"with_filter_access_cost": 0.077013594,
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"original_found_rows_cost": 0.546751728,
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"with_filter_found_rows_cost": 5.467517e-4,
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"org_cost": 0.60809449,
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"filter_cost": 0.077928803,
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"filter_used": true
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},
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"rows": 0.492,
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"cost": 0.077928803,
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"chosen": true
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},
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{
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"filter":
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{
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"rowid_filter_index": "idx2",
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"index_only_cost": 0.000881127,
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"filter_startup_cost": 0.066293508,
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"find_key_and_filter_lookup_cost": 8.646449e-5,
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"filter_selectivity": 0.492,
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"original_rows": 1,
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"new_rows": 0.492,
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"original_access_cost": 0.001992411,
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"with_filter_access_cost": 0.001514343,
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"original_found_rows_cost": 0.001111284,
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"with_filter_found_rows_cost": 5.467517e-4,
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"org_cost": 0.002024411,
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"filter_cost": 0.067823595,
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"filter_used": false
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},
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"access_type": "range",
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"range_index": "idx1",
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"rows": 1,
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"rows_after_filter": 1,
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"rows_out": 0.492,
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"cost": 0.002574553,
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"chosen": true
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}
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]
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]
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The following trace should have a different rowid_filter_key cost
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set statement optimizer_adjust_secondary_key_costs=2 for
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explain select * from t1 where nm like '500%' AND fl2 = 0;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 range idx1,idx2 idx1 35 NULL 1 Using index condition; Using where
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Warnings:
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Warning 1287 '@@optimizer_adjust_secondary_key_costs' is deprecated and will be removed in a future release
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Warning 1287 '@@optimizer_adjust_secondary_key_costs' is deprecated and will be removed in a future release
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set @trace=(select trace from information_schema.optimizer_trace);
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select json_detailed(json_extract(@trace, '$**.considered_access_paths'));
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json_detailed(json_extract(@trace, '$**.considered_access_paths'))
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[
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[
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{
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"access_type": "ref",
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"index": "idx2",
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"used_range_estimates": true,
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"filter":
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{
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"rowid_filter_index": "idx1",
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"index_only_cost": 0.045598762,
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"filter_startup_cost": 0.000899465,
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"find_key_and_filter_lookup_cost": 0.03086808,
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"filter_selectivity": 0.001,
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"original_rows": 492,
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"new_rows": 0.492,
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"original_access_cost": 0.59235049,
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"with_filter_access_cost": 0.077013594,
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"original_found_rows_cost": 0.546751728,
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"with_filter_found_rows_cost": 5.467517e-4,
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"org_cost": 0.60809449,
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"filter_cost": 0.077928803,
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"filter_used": true
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},
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"rows": 0.492,
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"cost": 0.077928803,
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"chosen": true
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},
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{
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"filter":
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{
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"rowid_filter_index": "idx2",
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"index_only_cost": 0.000881127,
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"filter_startup_cost": 0.066293508,
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"find_key_and_filter_lookup_cost": 8.646449e-5,
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"filter_selectivity": 0.492,
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"original_rows": 1,
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"new_rows": 0.492,
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"original_access_cost": 0.001992411,
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"with_filter_access_cost": 0.001514343,
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"original_found_rows_cost": 0.001111284,
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"with_filter_found_rows_cost": 5.467517e-4,
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"org_cost": 0.002024411,
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"filter_cost": 0.067823595,
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"filter_used": false
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},
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"access_type": "range",
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"range_index": "idx1",
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"rows": 1,
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"rows_after_filter": 1,
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"rows_out": 0.492,
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"cost": 0.002574553,
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"chosen": true
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}
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]
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]
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drop table t1, name, flag2;
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select @@optimizer_adjust_secondary_key_costs;
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@@optimizer_adjust_secondary_key_costs
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0
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set @@optimizer_adjust_secondary_key_costs=7;
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Warnings:
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Warning 1287 '@@optimizer_adjust_secondary_key_costs' is deprecated and will be removed in a future release
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Warning 1292 Truncated incorrect optimizer_adjust_secondary_ke... value: '7'
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select @@optimizer_adjust_secondary_key_costs;
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@@optimizer_adjust_secondary_key_costs
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2
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set @@optimizer_adjust_secondary_key_costs=default;
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Warnings:
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Warning 1287 '@@optimizer_adjust_secondary_key_costs' is deprecated and will be removed in a future release
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#
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# MDEV-34664: fix_innodb_cardinality
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#
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set @save_userstat=@@global.userstat;
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set @save_ispsp=@@global.innodb_stats_persistent_sample_pages;
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set @@global.innodb_stats_persistent_sample_pages=20;
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set @@global.userstat=on;
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set use_stat_tables=PREFERABLY_FOR_QUERIES;
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create or replace table t1 (a int primary key, b int, c int, d int, key(b,c,d)) engine=innodb;
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insert into t1 select seq,seq/100,seq/60,seq/10 from seq_1_to_1000;
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create or replace table t2 (a int);
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insert into t2 values (1),(2),(3);
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analyze table t1;
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Table Op Msg_type Msg_text
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test.t1 analyze status OK
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select count(distinct b),count(distinct b,c), count(distinct b,c,d) from t1;
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count(distinct b) count(distinct b,c) count(distinct b,c,d)
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11 25 125
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show index from t1;
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Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment Index_comment Ignored
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t1 0 PRIMARY 1 a A 1000 NULL NULL BTREE NO
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t1 1 b 1 b A 11 NULL NULL YES BTREE NO
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t1 1 b 2 c A 25 NULL NULL YES BTREE NO
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t1 1 b 3 d A 125 NULL NULL YES BTREE NO
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explain select * from t1,t2 where t1.b=t2.a;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t2 ALL NULL NULL NULL NULL 3 Using where
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1 SIMPLE t1 ref b b 5 test.t2.a 90 Using index
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set @@optimizer_adjust_secondary_key_costs=8;
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Warnings:
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Warning 1287 '@@optimizer_adjust_secondary_key_costs' is deprecated and will be removed in a future release
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Warning 1292 Truncated incorrect optimizer_adjust_secondary_ke... value: '8'
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explain select * from t1,t2 where t1.b=t2.a;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t2 ALL NULL NULL NULL NULL 3 Using where
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1 SIMPLE t1 ref b b 5 test.t2.a 90 Using index
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show index from t1;
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Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment Index_comment Ignored
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t1 0 PRIMARY 1 a A 1000 NULL NULL BTREE NO
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t1 1 b 1 b A 11 NULL NULL YES BTREE NO
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t1 1 b 2 c A 25 NULL NULL YES BTREE NO
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t1 1 b 3 d A 125 NULL NULL YES BTREE NO
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flush tables;
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explain select * from t1,t2 where t1.b=t2.a;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t2 ALL NULL NULL NULL NULL 3 Using where
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1 SIMPLE t1 ref b b 5 test.t2.a 90 Using index
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show index from t1;
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Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment Index_comment Ignored
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t1 0 PRIMARY 1 a A 1000 NULL NULL BTREE NO
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t1 1 b 1 b A 11 NULL NULL YES BTREE NO
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t1 1 b 2 c A 25 NULL NULL YES BTREE NO
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t1 1 b 3 d A 125 NULL NULL YES BTREE NO
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connect user2, localhost, root,,;
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show index from t1;
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Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment Index_comment Ignored
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t1 0 PRIMARY 1 a A 1000 NULL NULL BTREE NO
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t1 1 b 1 b A 11 NULL NULL YES BTREE NO
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t1 1 b 2 c A 25 NULL NULL YES BTREE NO
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t1 1 b 3 d A 125 NULL NULL YES BTREE NO
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connection default;
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disconnect user2;
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drop table t1,t2;
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set global userstat=@save_userstat;
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set global innodb_stats_persistent_sample_pages=@save_ispsp;
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set @@optimizer_adjust_secondary_key_costs=default;
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Warnings:
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Warning 1287 '@@optimizer_adjust_secondary_key_costs' is deprecated and will be removed in a future release
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