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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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2
mysql-test/r/func_group.result
View File

@ -824,6 +824,7 @@ select 1, min(a) from t1m where 1=99;
1 NULL
select 1, min(1) from t1m where a=99;
1 min(1)
1 NULL
select 1, min(1) from t1m where 1=99;
1 min(1)
1 NULL
@ -835,6 +836,7 @@ select 1, max(a) from t1m where 1=99;
1 NULL
select 1, max(1) from t1m where a=99;
1 max(1)
1 NULL
select 1, max(1) from t1m where 1=99;
1 max(1)
1 NULL

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;

2
mysql-test/r/subselect.result
View File

@ -539,7 +539,7 @@ EXPLAIN EXTENDED SELECT MAX(numreponse) FROM t1 WHERE numeropost='1';
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
Warnings:
Note 1003 select max(test.t1.numreponse) AS `MAX(numreponse)` from test.t1 where (test.t1.numeropost = _latin1'1')
Note 1003 select max(test.t1.numreponse) AS `MAX(numreponse)` from test.t1
EXPLAIN EXTENDED SELECT numreponse FROM t1 WHERE numeropost='1' AND numreponse=(SELECT MAX(numreponse) FROM t1 WHERE numeropost='1');
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 const PRIMARY,numreponse PRIMARY 7 const,const 1 Using index

30
mysql-test/t/select.test
View File

@ -2297,4 +2297,34 @@ INSERT INTO t1 VALUES (10);
SELECT i='1e+01',i=1e+01, i in (1e+01), i in ('1e+01') FROM t1;
DROP TABLE t1;
#
# Bug #20954 "avg(keyval) retuns 0.38 but max(keyval) returns an empty set"
#
--disable_ps_protocol
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;
explain select max(key2) from t2 where key2 <= 1.6158;
explain select min(key1) from t1 where key1 >= 0.3762;
explain select min(key2) from t2 where key2 >= 1.3762;
explain select max(key1), min(key2) from t1, t2
where key1 <= 0.6158 and key2 >= 1.3762;
explain select max(key1) from t1 where key1 <= 0.6158 and rand() + 0.5 >= 0.5;
explain select min(key1) from t1 where key1 >= 0.3762 and rand() + 0.5 >= 0.5;
select max(key1) from t1 where key1 <= 0.6158;
select max(key2) from t2 where key2 <= 1.6158;
select min(key1) from t1 where key1 >= 0.3762;
select min(key2) from t2 where key2 >= 1.3762;
select max(key1), min(key2) from t1, t2
where key1 <= 0.6158 and key2 >= 1.3762;
select max(key1) from t1 where key1 <= 0.6158 and rand() + 0.5 >= 0.5;
select min(key1) from t1 where key1 >= 0.3762 and rand() + 0.5 >= 0.5;
DROP TABLE t1,t2;
--enable_ps_protocol
# End of 4.1 tests

18
sql/sql_select.cc
View File

@ -547,6 +547,24 @@ JOIN::optimize()
}
zero_result_cause= "Select tables optimized away";
tables_list= 0; // All tables resolved
/*
Extract all table-independent conditions and replace the WHERE
clause with them. All other conditions were computed by opt_sum_query
and the MIN/MAX/COUNT function(s) have been replaced by constants,
so there is no need to compute the whole WHERE clause again.
Notice that make_cond_for_table() will always succeed to remove all
computed conditions, because opt_sum_query() is applicable only to
conjunctions.
*/
if (conds)
{
COND *table_independent_conds=
make_cond_for_table(conds, PSEUDO_TABLE_BITS, 0);
DBUG_EXECUTE("where",
print_where(table_independent_conds,
"where after opt_sum_query()"););
conds= table_independent_conds;
}
}
}
if (!tables_list)