mariadb/mysql-test/r/index_merge_ror.result
unknown ef452e19bf BUG#14940 "MySQL choose wrong index", v.2
- Make the range-et-al optimizer produce E(#table records after table 
                                           condition is applied),
- Make the join optimizer use this value,
- Add "filtered" column to EXPLAIN EXTENDED to show 
  fraction of records left after table condition is applied
- Adjust test results, add comments


mysql-test/r/archive_gis.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/auto_increment.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/bdb_gis.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/bench_count_distinct.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/binlog_stm_blackhole.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/case.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/cast.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/compress.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/ctype_collate.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/ctype_cp1250_ch.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/date_formats.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/distinct.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/fulltext.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/func_compress.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/func_crypt.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/func_default.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/func_encrypt.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/func_gconcat.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/func_group.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/func_if.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/func_in.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/func_like.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/func_math.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/func_op.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/func_regexp.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/func_set.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/func_str.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/func_system.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/func_test.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/func_time.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/gis.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/group_by.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/group_min_max.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/having.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/heap.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/heap_hash.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/index_merge.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/index_merge_innodb.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/index_merge_ror.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/innodb_gis.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/insert_update.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/join.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/join_nested.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/key_diff.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/myisam.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/ndb_gis.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/negation_elimination.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/null.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/olap.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/partition_pruning.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/query_cache.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/row.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/rpl_get_lock.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/rpl_master_pos_wait.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/select.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/ssl.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/ssl_compress.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/subselect.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/type_blob.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/union.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/varbinary.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/variables.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/r/view.result:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/t/ctype_cp1250_ch.test:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/t/func_like.test:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/t/group_min_max.test:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/t/index_merge_ror.test:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/t/index_merge_ror_cpk.test:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/t/join.test:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
mysql-test/t/partition_pruning.test:
  BUG#14940: Adjust the test results: EXPLAIN EXTENDED now has extra "filtered" column
sql/opt_range.cc:
  BUG#14940: Make range/index_merge/group-min-max optimizer produce TABLE::quick_condition_rows -
    estimate of #records that will match the table condition.
sql/sql_class.cc:
  BUG#14940: Add "filtered" column to output of EXPLAIN EXTENDED
sql/sql_select.cc:
  BUG#14940: 
  - Make the join optimizer to use TABLE::quick_condition_rows=
    = E(#table records after filtering with table condition) 
  - Add "filtered" column to output of EXPLAIN EXTENDED
sql/sql_select.h:
  BUG#14940: Added comments
sql/table.h:
  BUG#14940: Added comments
2006-07-28 21:27:01 +04:00

196 lines
12 KiB
Text

drop table if exists t0,t1,t2;
select count(*) from t1;
count(*)
64801
explain select key1,key2 from t1 where key1=100 and key2=100;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index_merge key1,key2 key1,key2 5,5 NULL 77 Using intersect(key1,key2); Using where; Using index
select key1,key2 from t1 where key1=100 and key2=100;
key1 key2
100 100
explain select key1,key2,key3,key4,filler1 from t1 where key1=100 and key2=100 or key3=100 and key4=100;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index_merge key1,key2,key3,key4 key1,key2,key3,key4 5,5,5,5 NULL 154 Using union(intersect(key1,key2),intersect(key3,key4)); Using where
select key1,key2,key3,key4,filler1 from t1 where key1=100 and key2=100 or key3=100 and key4=100;
key1 key2 key3 key4 filler1
100 100 100 100 key1-key2-key3-key4
insert into t1 (key1, key2, key3, key4, filler1) values (100, 100, -1, -1, 'key1-key2');
insert into t1 (key1, key2, key3, key4, filler1) values (-1, -1, 100, 100, 'key4-key3');
explain select key1,key2,filler1 from t1 where key1=100 and key2=100;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index_merge key1,key2 key1,key2 5,5 NULL 77 Using intersect(key1,key2); Using where
select key1,key2,filler1 from t1 where key1=100 and key2=100;
key1 key2 filler1
100 100 key1-key2-key3-key4
100 100 key1-key2
explain select key1,key2 from t1 where key1=100 and key2=100;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index_merge key1,key2 key1,key2 5,5 NULL 77 Using intersect(key1,key2); Using where; Using index
select key1,key2 from t1 where key1=100 and key2=100;
key1 key2
100 100
100 100
explain select key1,key2,key3,key4 from t1 where key1=100 and key2=100 or key3=100 and key4=100;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index_merge key1,key2,key3,key4 key1,key2,key3,key4 5,5,5,5 NULL 154 Using union(intersect(key1,key2),intersect(key3,key4)); Using where
select key1,key2,key3,key4 from t1 where key1=100 and key2=100 or key3=100 and key4=100;
key1 key2 key3 key4
100 100 100 100
100 100 -1 -1
-1 -1 100 100
explain select key1,key2,key3,key4,filler1 from t1 where key1=100 and key2=100 or key3=100 and key4=100;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index_merge key1,key2,key3,key4 key1,key2,key3,key4 5,5,5,5 NULL 154 Using union(intersect(key1,key2),intersect(key3,key4)); Using where
select key1,key2,key3,key4,filler1 from t1 where key1=100 and key2=100 or key3=100 and key4=100;
key1 key2 key3 key4 filler1
100 100 100 100 key1-key2-key3-key4
100 100 -1 -1 key1-key2
-1 -1 100 100 key4-key3
explain select key1,key2,key3 from t1 where key1=100 and key2=100 and key3=100;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index_merge key1,key2,key3 key1,key2,key3 5,5,5 NULL 2 Using intersect(key1,key2,key3); Using where; Using index
select key1,key2,key3 from t1 where key1=100 and key2=100 and key3=100;
key1 key2 key3
100 100 100
insert into t1 (key1,key2,key3,key4,filler1) values (101,101,101,101, 'key1234-101');
explain select key1,key2,key3,key4,filler1 from t1 where key1=100 and key2=100 or key3=101;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index_merge key1,key2,key3 key1,key2,key3 5,5,5 NULL 83 Using union(intersect(key1,key2),key3); Using where
select key1,key2,key3,key4,filler1 from t1 where key1=100 and key2=100 or key3=101;
key1 key2 key3 key4 filler1
100 100 100 100 key1-key2-key3-key4
100 100 -1 -1 key1-key2
101 101 101 101 key1234-101
select key1,key2, filler1 from t1 where key1=100 and key2=100;
key1 key2 filler1
100 100 key1-key2-key3-key4
100 100 key1-key2
update t1 set filler1='to be deleted' where key1=100 and key2=100;
update t1 set key1=200,key2=200 where key1=100 and key2=100;
delete from t1 where key1=200 and key2=200;
select key1,key2,filler1 from t1 where key2=100 and key2=200;
key1 key2 filler1
explain select key1,key2,key3,key4,filler1 from t1 where key1=100 and key2=100 or key3=100 and key4=100;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index_merge key1,key2,key3,key4 key1,key2,key3,key4 5,5,5,5 NULL 152 Using union(intersect(key1,key2),intersect(key3,key4)); Using where
select key1,key2,key3,key4,filler1 from t1 where key1=100 and key2=100 or key3=100 and key4=100;
key1 key2 key3 key4 filler1
-1 -1 100 100 key4-key3
delete from t1 where key3=100 and key4=100;
explain select key1,key2,key3,key4,filler1 from t1 where key1=100 and key2=100 or key3=100 and key4=100;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index_merge key1,key2,key3,key4 key1,key2,key3,key4 5,5,5,5 NULL 152 Using union(intersect(key1,key2),intersect(key3,key4)); Using where
select key1,key2,key3,key4,filler1 from t1 where key1=100 and key2=100 or key3=100 and key4=100;
key1 key2 key3 key4 filler1
explain select key1,key2 from t1 where key1=100 and key2=100;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index_merge key1,key2 key1,key2 5,5 NULL 76 Using intersect(key1,key2); Using where; Using index
select key1,key2 from t1 where key1=100 and key2=100;
key1 key2
insert into t1 (key1, key2, key3, key4, filler1) values (100, 100, 200, 200,'key1-key2-key3-key4-1');
insert into t1 (key1, key2, key3, key4, filler1) values (100, 100, 200, 200,'key1-key2-key3-key4-2');
insert into t1 (key1, key2, key3, key4, filler1) values (100, 100, 200, 200,'key1-key2-key3-key4-3');
explain select key1,key2,key3,key4,filler1 from t1 where key3=200 or (key1=100 and key2=100) or key4=200;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index_merge key1,key2,key3,key4 key3,key1,key2,key4 5,5,5,5 NULL 136 Using union(key3,intersect(key1,key2),key4); Using where
select key1,key2,key3,key4,filler1 from t1 where key3=200 or (key1=100 and key2=100) or key4=200;
key1 key2 key3 key4 filler1
100 100 200 200 key1-key2-key3-key4-3
100 100 200 200 key1-key2-key3-key4-2
100 100 200 200 key1-key2-key3-key4-1
insert into t1 (key1, key2, key3, key4, filler1) values (-1, -1, -1, 200,'key4');
explain select key1,key2,key3,key4,filler1 from t1 where key3=200 or (key1=100 and key2=100) or key4=200;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index_merge key1,key2,key3,key4 key3,key1,key2,key4 5,5,5,5 NULL 146 Using union(key3,intersect(key1,key2),key4); Using where
select key1,key2,key3,key4,filler1 from t1 where key3=200 or (key1=100 and key2=100) or key4=200;
key1 key2 key3 key4 filler1
100 100 200 200 key1-key2-key3-key4-3
100 100 200 200 key1-key2-key3-key4-2
100 100 200 200 key1-key2-key3-key4-1
-1 -1 -1 200 key4
insert into t1 (key1, key2, key3, key4, filler1) values (-1, -1, 200, -1,'key3');
explain select key1,key2,key3,key4,filler1 from t1 where key3=200 or (key1=100 and key2=100) or key4=200;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index_merge key1,key2,key3,key4 key3,key1,key2,key4 5,5,5,5 NULL 156 Using union(key3,intersect(key1,key2),key4); Using where
select key1,key2,key3,key4,filler1 from t1 where key3=200 or (key1=100 and key2=100) or key4=200;
key1 key2 key3 key4 filler1
100 100 200 200 key1-key2-key3-key4-3
100 100 200 200 key1-key2-key3-key4-2
100 100 200 200 key1-key2-key3-key4-1
-1 -1 -1 200 key4
-1 -1 200 -1 key3
explain select * from t1 where st_a=1 and st_b=1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index_merge sta_swt12a,sta_swt1a,sta_swt2a,sta_swt21a,st_a,stb_swt1a_2b,stb_swt1b,st_b st_a,st_b 4,4 NULL 3515 Using intersect(st_a,st_b); Using where
explain select st_a,st_b from t1 where st_a=1 and st_b=1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index_merge sta_swt12a,sta_swt1a,sta_swt2a,sta_swt21a,st_a,stb_swt1a_2b,stb_swt1b,st_b st_a,st_b 4,4 NULL 3515 Using intersect(st_a,st_b); Using where; Using index
explain select st_a from t1 ignore index (st_a) where st_a=1 and st_b=1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ref sta_swt12a,sta_swt1a,sta_swt2a,sta_swt21a,stb_swt1a_2b,stb_swt1b,st_b st_b 4 const 15093 Using where
explain select * from t1 where st_a=1 and swt1a=1 and swt2a=1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ref sta_swt12a,sta_swt1a,sta_swt2a,sta_swt21a,st_a sta_swt21a 12 const,const,const 971
explain select * from t1 where st_b=1 and swt1b=1 and swt2b=1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ref stb_swt1a_2b,stb_swt1b,st_b stb_swt1a_2b 8 const,const 3879 Using where
explain select * from t1 where st_a=1 and swt1a=1 and swt2a=1 and st_b=1 and swt1b=1 and swt2b=1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index_merge sta_swt12a,sta_swt1a,sta_swt2a,sta_swt21a,st_a,stb_swt1a_2b,stb_swt1b,st_b sta_swt12a,stb_swt1a_2b 12,12 NULL 58 Using intersect(sta_swt12a,stb_swt1a_2b); Using where
explain select * from t1 ignore index (sta_swt21a, stb_swt1a_2b)
where st_a=1 and swt1a=1 and swt2a=1 and st_b=1 and swt1b=1 and swt2b=1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index_merge sta_swt12a,sta_swt1a,sta_swt2a,st_a,stb_swt1b,st_b sta_swt12a,stb_swt1b 12,8 NULL 58 Using intersect(sta_swt12a,stb_swt1b); Using where
explain select * from t1 ignore index (sta_swt21a, sta_swt12a, stb_swt1a_2b)
where st_a=1 and swt1a=1 and swt2a=1 and st_b=1 and swt1b=1 and swt2b=1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index_merge sta_swt1a,sta_swt2a,st_a,stb_swt1b,st_b sta_swt1a,sta_swt2a,stb_swt1b 8,8,8 NULL 57 Using intersect(sta_swt1a,sta_swt2a,stb_swt1b); Using where
explain select * from t1 ignore index (sta_swt21a, sta_swt12a, stb_swt1a_2b, stb_swt1b)
where st_a=1 and swt1a=1 and swt2a=1 and st_b=1 and swt1b=1 and swt2b=1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index_merge sta_swt1a,sta_swt2a,st_a,st_b sta_swt1a,sta_swt2a,st_b 8,8,4 NULL 223 Using intersect(sta_swt1a,sta_swt2a,st_b); Using where
explain select * from t1
where st_a=1 and swt1a=1 and swt2a=1 and st_b=1 and swt1b=1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index_merge sta_swt12a,sta_swt1a,sta_swt2a,sta_swt21a,st_a,stb_swt1a_2b,stb_swt1b,st_b sta_swt12a,stb_swt1a_2b 12,12 NULL 58 Using intersect(sta_swt12a,stb_swt1a_2b); Using where
explain select * from t1
where st_a=1 and swt1a=1 and st_b=1 and swt1b=1 and swt1b=1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index_merge sta_swt12a,sta_swt1a,sta_swt2a,sta_swt21a,st_a,stb_swt1a_2b,stb_swt1b,st_b sta_swt1a,stb_swt1b 8,8 NULL 232 Using intersect(sta_swt1a,stb_swt1b); Using where
explain select st_a from t1
where st_a=1 and swt1a=1 and st_b=1 and swt1b=1 and swt1b=1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index_merge sta_swt12a,sta_swt1a,sta_swt2a,sta_swt21a,st_a,stb_swt1a_2b,stb_swt1b,st_b sta_swt1a,stb_swt1b 8,8 NULL 232 Using intersect(sta_swt1a,stb_swt1b); Using where; Using index
explain select st_a from t1
where st_a=1 and swt1a=1 and st_b=1 and swt1b=1 and swt1b=1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index_merge sta_swt12a,sta_swt1a,sta_swt2a,sta_swt21a,st_a,stb_swt1a_2b,stb_swt1b,st_b sta_swt1a,stb_swt1b 8,8 NULL 232 Using intersect(sta_swt1a,stb_swt1b); Using where; Using index
drop table t0,t1;
create table t2 (
a char(10),
b char(10),
filler1 char(255),
filler2 char(255),
key(a(5)),
key(b(5))
);
select count(a) from t2 where a='BBBBBBBB';
count(a)
4
select count(a) from t2 where b='BBBBBBBB';
count(a)
4
expla_or_bin select count(a_or_b) from t2 where a_or_b='AAAAAAAA' a_or_bnd a_or_b='AAAAAAAA';
id select_type ta_or_ba_or_ble type possia_or_ble_keys key key_len ref rows Extra_or_b
1 SIMPLE t2 ref a_or_b,a_or_b a_or_b 6 const 4 Using where
select count(a) from t2 where a='AAAAAAAA' and b='AAAAAAAA';
count(a)
4
select count(a) from t2 ignore index(a,b) where a='AAAAAAAA' and b='AAAAAAAA';
count(a)
4
insert into t2 values ('ab', 'ab', 'uh', 'oh');
explain select a from t2 where a='ab';
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 ref a a 6 const 1 Using where
drop table t2;