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Fix for BUG#20954: avg(keyval) retuns 0.38 but max(keyval) returns an empty set

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The problem was in that opt_sum_query() replaced MIN/MAX functions
with the corresponding constant found in a key, but due to imprecise
representation of float numbers, when evaluating the where clause,
this comparison failed.

When MIN/MAX optimization detects that all tables can be removed,
also remove all conjuncts in a where clause that refer to these
tables. As a result of this fix, these conditions are not evaluated
twice, and in the case of float number comparisons we do not discard
result rows due to imprecise float representation.

As a side-effect this fix also corrects an unnoticed problem in
bug 12882.
This commit is contained in:
timour/timka@lamia.home
2006-07-26 01:11:19 +03:00
parent bffd438de3
commit 86ae2f3b06
5 changed files with 100 additions and 1 deletions
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49
mysql-test/r/select.result
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@@ -2744,3 +2744,52 @@ SELECT i='1e+01',i=1e+01, i in (1e+01), i in ('1e+01') FROM t1;
i='1e+01' i=1e+01 i in (1e+01) i in ('1e+01')
0 1 1 1
DROP TABLE t1;
CREATE TABLE t1 (key1 float default NULL, UNIQUE KEY key1 (key1));
CREATE TABLE t2 (key2 float default NULL, UNIQUE KEY key2 (key2));
INSERT INTO t1 VALUES (0.3762),(0.3845),(0.6158),(0.7941);
INSERT INTO t2 VALUES (1.3762),(1.3845),(1.6158),(1.7941);
explain select max(key1) from t1 where key1 <= 0.6158;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Select tables optimized away
explain select max(key2) from t2 where key2 <= 1.6158;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Select tables optimized away
explain select min(key1) from t1 where key1 >= 0.3762;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Select tables optimized away
explain select min(key2) from t2 where key2 >= 1.3762;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Select tables optimized away
explain select max(key1), min(key2) from t1, t2
where key1 <= 0.6158 and key2 >= 1.3762;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Select tables optimized away
explain select max(key1) from t1 where key1 <= 0.6158 and rand() + 0.5 >= 0.5;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Select tables optimized away
explain select min(key1) from t1 where key1 >= 0.3762 and rand() + 0.5 >= 0.5;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Select tables optimized away
select max(key1) from t1 where key1 <= 0.6158;
max(key1)
0.61580002307892
select max(key2) from t2 where key2 <= 1.6158;
max(key2)
1.6158000230789
select min(key1) from t1 where key1 >= 0.3762;
min(key1)
0.37619999051094
select min(key2) from t2 where key2 >= 1.3762;
min(key2)
1.3761999607086
select max(key1), min(key2) from t1, t2
where key1 <= 0.6158 and key2 >= 1.3762;
max(key1) min(key2)
0.61580002307892 1.3761999607086
select max(key1) from t1 where key1 <= 0.6158 and rand() + 0.5 >= 0.5;
max(key1)
0.61580002307892
select min(key1) from t1 where key1 >= 0.3762 and rand() + 0.5 >= 0.5;
min(key1)
0.37619999051094
DROP TABLE t1,t2;