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MDEV-27230: Estimation for filtered rows less precise ...

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Fix the code in Histogram_json_hb::range_selectivity that handles
special cases: a non-inclusive endpoint hitting a bucket boundary...
This commit is contained in:
Sergei Petrunia 2021-12-13 23:46:04 +03:00
parent 08f1c4a2e0
commit 905634dc3f
3 changed files with 28 additions and 0 deletions
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17
mysql-test/main/statistics_json.result
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@ -8194,3 +8194,20 @@ analyze select * from t2 where a =100;
id select_type table type possible_keys key key_len ref rows r_rows filtered r_filtered Extra id select_type table type possible_keys key key_len ref rows r_rows filtered r_filtered Extra
1 SIMPLE t2 ALL NULL NULL NULL NULL 1011 1011.00 0.10 0.10 Using where 1 SIMPLE t2 ALL NULL NULL NULL NULL 1011 1011.00 0.10 0.10 Using where
drop table t0,t1,t2; drop table t0,t1,t2;
#
# MDEV-27230: Estimation for filtered rows less precise ...
#
create table t1 (a char(1));
insert into t1 select chr(seq%26+97) from seq_1_to_50;
insert into t1 select ':' from t1;
analyze table t1 persistent for all;
Table Op Msg_type Msg_text
test.t1 analyze status Engine-independent statistics collected
test.t1 analyze status OK
analyze select COUNT(*) FROM t1 WHERE a <> 'a';
id select_type table type possible_keys key key_len ref rows r_rows filtered r_filtered Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 100 100.00 99.00 99.00 Using where
analyze select COUNT(*) FROM t1 WHERE a < 'a';
id select_type table type possible_keys key key_len ref rows r_rows filtered r_filtered Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 100 100.00 50.00 50.00 Using where
drop table t1;

10
mysql-test/main/statistics_json.test
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@ -380,3 +380,13 @@ analyze select * from t2 where a =100;
drop table t0,t1,t2; drop table t0,t1,t2;
--echo #
--echo # MDEV-27230: Estimation for filtered rows less precise ...
--echo #
create table t1 (a char(1));
insert into t1 select chr(seq%26+97) from seq_1_to_50;
insert into t1 select ':' from t1;
analyze table t1 persistent for all;
analyze select COUNT(*) FROM t1 WHERE a <> 'a';
analyze select COUNT(*) FROM t1 WHERE a < 'a';
drop table t1;

1
sql/opt_histogram_json.cc
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@ -1022,6 +1022,7 @@ double Histogram_json_hb::range_selectivity(Field *field, key_range *min_endp,
$CONST. Move to the previous bucket. $CONST. Move to the previous bucket.
*/ */
idx--; idx--;
equal= false;
} }
double left_fract= get_left_fract(idx); double left_fract= get_left_fract(idx);