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SET eq_range_index_dive_limit=default;
SELECT @@eq_range_index_dive_limit;
@@eq_range_index_dive_limit
10
CREATE TABLE t1
(
/* Field names reflect value(rowid) distribution, st=STairs, swt= SaWTooth */
st_a int,
swt1a int,
swt2a int,
st_b int,
swt1b int,
swt2b int,
key sta_swt12a(st_a,swt1a,swt2a),
key sta_swt1a(st_a,swt1a),
key sta_swt2a(st_a,swt2a),
key sta_swt21a(st_a,swt2a,swt1a),
key st_a(st_a),
key stb_swt1a_2b(st_b,swt1b,swt2a),
key stb_swt1b(st_b,swt1b),
key st_b(st_b)
) ;
ALTER TABLE t1 DISABLE KEYS;
#
# Printing of many insert into t1 disabled.
#
ALTER TABLE t1 ENABLE KEYS;
ANALYZE TABLE t1;
Table Op Msg_type Msg_text
test.t1 analyze status Table is already up to date
#
# Run index_merge queries two times: 1) with index dives
# 2) with index statistics
#
explain
select * from t1
where st_a=1 and swt1a=1 and swt2a=1 and st_b=1 and swt1b=1 and swt2b=1 limit 5;
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 15,15 NULL 3 Using intersect(sta_swt12a,stb_swt1a_2b); Using where
select * from t1
where st_a=1 and swt1a=1 and swt2a=1 and st_b=1 and swt1b=1 and swt2b=1 limit 5;
st_a swt1a swt2a st_b swt1b swt2b
1 1 1 1 1 1
1 1 1 1 1 1
1 1 1 1 1 1
1 1 1 1 1 1
1 1 1 1 1 1
explain
select * from t1
where st_a=1 and swt1a=1 and swt2a=1 and st_b=1 and swt1b=1 limit 5;
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 15,15 NULL 3 Using intersect(sta_swt12a,stb_swt1a_2b); Using where
select * from t1
where st_a=1 and swt1a=1 and swt2a=1 and st_b=1 and swt1b=1 limit 5;
st_a swt1a swt2a st_b swt1b swt2b
1 1 1 1 1 1
1 1 1 1 1 1
1 1 1 1 1 1
1 1 1 1 1 1
1 1 1 1 1 1
explain
select * from t1
where st_a=1 and swt1a=1 and st_b=1 and swt1b=1 and swt1b=1 limit 5;
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,stb_swt1a_2b,stb_swt1b,st_b sta_swt12a 10 const,const 89 Using where
select * from t1
where st_a=1 and swt1a=1 and st_b=1 and swt1b=1 and swt1b=1 limit 5;
st_a swt1a swt2a st_b swt1b swt2b
1 1 1 1 1 1
1 1 1 1 1 1
1 1 1 1 1 1
1 1 1 1 1 1
1 1 1 1 1 1
SET eq_range_index_dive_limit=1;
SET SESSION DEBUG="+d,crash_records_in_range";
explain
select * from t1
where st_a=1 and swt1a=1 and swt2a=1 and st_b=1 and swt1b=1 and swt2b=1 limit 5;
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 15,15 NULL 3 Using intersect(sta_swt12a,stb_swt1a_2b); Using where
select * from t1
where st_a=1 and swt1a=1 and swt2a=1 and st_b=1 and swt1b=1 and swt2b=1 limit 5;
st_a swt1a swt2a st_b swt1b swt2b
1 1 1 1 1 1
1 1 1 1 1 1
1 1 1 1 1 1
1 1 1 1 1 1
1 1 1 1 1 1
explain
select * from t1
where st_a=1 and swt1a=1 and swt2a=1 and st_b=1 and swt1b=1 limit 5;
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 15,15 NULL 3 Using intersect(sta_swt12a,stb_swt1a_2b); Using where
select * from t1
where st_a=1 and swt1a=1 and swt2a=1 and st_b=1 and swt1b=1 limit 5;
st_a swt1a swt2a st_b swt1b swt2b
1 1 1 1 1 1
1 1 1 1 1 1
1 1 1 1 1 1
1 1 1 1 1 1
1 1 1 1 1 1
explain
select * from t1
where st_a=1 and swt1a=1 and st_b=1 and swt1b=1 and swt1b=1 limit 5;
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,stb_swt1a_2b,stb_swt1b,st_b sta_swt12a 10 const,const 90 Using where
select * from t1
where st_a=1 and swt1a=1 and st_b=1 and swt1b=1 and swt1b=1 limit 5;
st_a swt1a swt2a st_b swt1b swt2b
1 1 1 1 1 1
1 1 1 1 1 1
1 1 1 1 1 1
1 1 1 1 1 1
1 1 1 1 1 1
SET eq_range_index_dive_limit=1;
SET SESSION DEBUG="+d,crash_records_in_range";
DROP TABLE t1;
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