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Fix for BUG#11185.
The source of the problem is in Field_longlong::cmp. If 'this' is an unsigned number, the method casts both the current value, and the constant that we compare with to an unsigned number. As a result if the constant we compare with is a negative number, it wraps to some unsigned number, and the comparison is incorrect. When the optimizer chooses the "range" access method, this problem causes handler::read_range_next to reject the current key when the upper bound key is a negative number because handler::compare_key incorrectly considers the positive and negative keys to be equal. The current patch does not correct the source of the problem in Field_longlong::cmp because it is not easy to propagate sign information about the constant at query execution time. Instead the patch changes the range optimizer so that it never compares unsiged fields with negative constants. As an added benefit, queries that do such comparisons will execute faster because the range optimizer replaces conditions like: (a) (unsigned_int [< | <=] negative_constant) == FALSE (b) (unsigned_int [> | >=] negative_constant) == TRUE with the corresponding constants. In some cases this may even result in constant time execution. mysql-test/r/range.result: - Added test for BUG#11185 - Added missing test from 4.1. This test also tests the fix for BUG#11185. mysql-test/t/range.test: - Added test for BUG#11185 - Added missing test from 4.1. This test also tests the fix for BUG#11185. sql/opt_range.cc: Added a new optimization to the range optimizer where we detect that an UNSIGNED field is compared with a negative constant. Depending on the comparison operator, we know directly that the result of the comparison is either TRUE or FALSE for all input values, and we need not check each value. This optimization is also necessary so that the index range access method produces correct results when comparing unsigned fields with negative constants.
This commit is contained in:
@ -544,11 +544,71 @@ count(*)
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select count(*) from t2 where x > -16;
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count(*)
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1
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2
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select count(*) from t2 where x = 18446744073709551601;
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count(*)
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0
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drop table t1,t2;
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create table t1 (x bigint unsigned not null primary key) engine=innodb;
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insert into t1(x) values (0xfffffffffffffff0);
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insert into t1(x) values (0xfffffffffffffff1);
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select * from t1;
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x
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18446744073709551600
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18446744073709551601
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select count(*) from t1 where x>0;
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count(*)
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2
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select count(*) from t1 where x=0;
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count(*)
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0
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select count(*) from t1 where x<0;
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count(*)
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0
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select count(*) from t1 where x < -16;
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count(*)
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0
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select count(*) from t1 where x = -16;
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count(*)
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0
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select count(*) from t1 where x > -16;
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count(*)
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2
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select count(*) from t1 where x = 18446744073709551601;
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count(*)
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1
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drop table t1;
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create table t1 (a bigint unsigned);
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create index t1i on t1(a);
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insert into t1 select 18446744073709551615;
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insert into t1 select 18446744073709551614;
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explain select * from t1 where a <> -1;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 index t1i t1i 9 NULL 2 Using where; Using index
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select * from t1 where a <> -1;
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a
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18446744073709551614
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18446744073709551615
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explain select * from t1 where a > -1 or a < -1;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 index t1i t1i 9 NULL 2 Using where; Using index
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select * from t1 where a > -1 or a < -1;
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a
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18446744073709551614
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18446744073709551615
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explain select * from t1 where a > -1;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 index t1i t1i 9 NULL 2 Using where; Using index
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select * from t1 where a > -1;
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a
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18446744073709551614
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18446744073709551615
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explain select * from t1 where a < -1;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
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select * from t1 where a < -1;
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a
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drop table t1;
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set names latin1;
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create table t1 (a char(10), b text, key (a)) character set latin1;
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INSERT INTO t1 (a) VALUES
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