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Bug #25207522: INCORRECT ORDER-BY BEHAVIOR ON A PARTITIONED TABLE WIT…
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…H A COMPOSITE PREFIX INDEX

Fix prefix key comparison in partitioning. Comparions must
take into account no more than prefix_len characters.

It used to compare prefix_len*mbmaxlen bytes.
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@vuvova
vuvova committed Jul 29, 2020
1 parent d597077 commit 0b5b2f8
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Showing 5 changed files with 136 additions and 24 deletions.
40 changes: 40 additions & 0 deletions mysql-test/r/partition.result
View file
Expand Up @@ -2756,5 +2756,45 @@ SELECT 1 FROM t1 WHERE a XOR 'a';
1
DROP TABLE t1;
#
# Bug #25207522: INCORRECT ORDER-BY BEHAVIOR ON A PARTITIONED TABLE
# WITH A COMPOSITE PREFIX INDEX
#
create table t1(id int unsigned not null,
data varchar(2) default null,
key data_idx (data(1),id)
) default charset=utf8
partition by range (id) (
partition p10 values less than (10),
partition p20 values less than (20)
);
insert t1 values (6, 'ab'), (4, 'ab'), (5, 'ab'), (16, 'ab'), (14, 'ab'), (15, 'ab'), (5, 'ac'), (15, 'aa') ;
select id from t1 where data = 'ab' order by id;
id
4
5
6
14
15
16
drop table t1;
create table t1(id int unsigned not null,
data text default null,
key data_idx (data(1),id)
) default charset=utf8
partition by range (id) (
partition p10 values less than (10),
partition p20 values less than (20)
);
insert t1 values (6, 'ab'), (4, 'ab'), (5, 'ab'), (16, 'ab'), (14, 'ab'), (15, 'ab'), (5, 'ac'), (15, 'aa') ;
select id from t1 where data = 'ab' order by id;
id
4
5
6
14
15
16
drop table t1;
#
# End of 10.1 tests
#
28 changes: 28 additions & 0 deletions mysql-test/t/partition.test
View file
Expand Up @@ -2970,6 +2970,34 @@ CREATE TABLE t1(a BINARY(80)) PARTITION BY KEY(a) PARTITIONS 3;
SELECT 1 FROM t1 WHERE a XOR 'a';
DROP TABLE t1;

--echo #
--echo # Bug #25207522: INCORRECT ORDER-BY BEHAVIOR ON A PARTITIONED TABLE
--echo # WITH A COMPOSITE PREFIX INDEX
--echo #
create table t1(id int unsigned not null,
data varchar(2) default null,
key data_idx (data(1),id)
) default charset=utf8
partition by range (id) (
partition p10 values less than (10),
partition p20 values less than (20)
);
insert t1 values (6, 'ab'), (4, 'ab'), (5, 'ab'), (16, 'ab'), (14, 'ab'), (15, 'ab'), (5, 'ac'), (15, 'aa') ;
select id from t1 where data = 'ab' order by id;
drop table t1;

create table t1(id int unsigned not null,
data text default null,
key data_idx (data(1),id)
) default charset=utf8
partition by range (id) (
partition p10 values less than (10),
partition p20 values less than (20)
);
insert t1 values (6, 'ab'), (4, 'ab'), (5, 'ab'), (16, 'ab'), (14, 'ab'), (15, 'ab'), (5, 'ac'), (15, 'aa') ;
select id from t1 where data = 'ab' order by id;
drop table t1;

--echo #
--echo # End of 10.1 tests
--echo #
66 changes: 55 additions & 11 deletions sql/field.cc
View file
Expand Up @@ -7537,8 +7537,7 @@ my_decimal *Field_varstring::val_decimal(my_decimal *decimal_value)
}


int Field_varstring::cmp_max(const uchar *a_ptr, const uchar *b_ptr,
uint max_len)
int Field_varstring::cmp(const uchar *a_ptr, const uchar *b_ptr)
{
uint a_length, b_length;
int diff;
Expand All @@ -7553,8 +7552,8 @@ int Field_varstring::cmp_max(const uchar *a_ptr, const uchar *b_ptr,
a_length= uint2korr(a_ptr);
b_length= uint2korr(b_ptr);
}
set_if_smaller(a_length, max_len);
set_if_smaller(b_length, max_len);
set_if_smaller(a_length, field_length);
set_if_smaller(b_length, field_length);
diff= field_charset->coll->strnncollsp(field_charset,
a_ptr+
length_bytes,
Expand All @@ -7566,6 +7565,43 @@ int Field_varstring::cmp_max(const uchar *a_ptr, const uchar *b_ptr,
}


static int cmp_str_prefix(const uchar *ua, size_t alen, const uchar *ub,
size_t blen, size_t prefix, CHARSET_INFO *cs)
{
const char *a= (char*)ua, *b= (char*)ub;
MY_STRCOPY_STATUS status;
prefix/= cs->mbmaxlen;
alen= cs->cset->well_formed_char_length(cs, a, a + alen, prefix, &status);
blen= cs->cset->well_formed_char_length(cs, b, b + blen, prefix, &status);
return cs->coll->strnncollsp(cs, ua, alen, ub, blen, 0);
}



int Field_varstring::cmp_prefix(const uchar *a_ptr, const uchar *b_ptr,
size_t prefix_len)
{
/* avoid expensive well_formed_char_length if possible */
if (prefix_len == table->field[field_index]->field_length)
return Field_varstring::cmp(a_ptr, b_ptr);

size_t a_length, b_length;

if (length_bytes == 1)
{
a_length= *a_ptr;
b_length= *b_ptr;
}
else
{
a_length= uint2korr(a_ptr);
b_length= uint2korr(b_ptr);
}
return cmp_str_prefix(a_ptr+length_bytes, a_length, b_ptr+length_bytes,
b_length, prefix_len, field_charset);
}


/**
@note
varstring and blob keys are ALWAYS stored with a 2 byte length prefix
Expand Down Expand Up @@ -8114,16 +8150,24 @@ int Field_blob::cmp(const uchar *a,uint32 a_length, const uchar *b,
}


int Field_blob::cmp_max(const uchar *a_ptr, const uchar *b_ptr,
uint max_length)
int Field_blob::cmp(const uchar *a_ptr, const uchar *b_ptr)
{
uchar *blob1,*blob2;
memcpy(&blob1, a_ptr+packlength, sizeof(char*));
memcpy(&blob2, b_ptr+packlength, sizeof(char*));
size_t a_len= get_length(a_ptr), b_len= get_length(b_ptr);
return cmp(blob1, a_len, blob2, b_len);
}


int Field_blob::cmp_prefix(const uchar *a_ptr, const uchar *b_ptr,
size_t prefix_len)
{
uchar *blob1,*blob2;
memcpy(&blob1, a_ptr+packlength, sizeof(char*));
memcpy(&blob2, b_ptr+packlength, sizeof(char*));
uint a_len= get_length(a_ptr), b_len= get_length(b_ptr);
set_if_smaller(a_len, max_length);
set_if_smaller(b_len, max_length);
return Field_blob::cmp(blob1,a_len,blob2,b_len);
size_t a_len= get_length(a_ptr), b_len= get_length(b_ptr);
return cmp_str_prefix(blob1, a_len, blob2, b_len, prefix_len, field_charset);
}


Expand Down Expand Up @@ -9407,7 +9451,7 @@ my_decimal *Field_bit::val_decimal(my_decimal *deciaml_value)
The a and b pointer must be pointers to the field in a record
(not the table->record[0] necessarily)
*/
int Field_bit::cmp_max(const uchar *a, const uchar *b, uint max_len)
int Field_bit::cmp_prefix(const uchar *a, const uchar *b, size_t prefix_len)
{
my_ptrdiff_t a_diff= a - ptr;
my_ptrdiff_t b_diff= b - ptr;
Expand Down
22 changes: 11 additions & 11 deletions sql/field.h
View file
Expand Up @@ -954,9 +954,13 @@ class Field: public Value_source
return type();
}
inline int cmp(const uchar *str) { return cmp(ptr,str); }
virtual int cmp_max(const uchar *a, const uchar *b, uint max_len)
{ return cmp(a, b); }
virtual int cmp(const uchar *,const uchar *)=0;
/*
The following method is used for comparing prefix keys.
Currently it's only used in partitioning.
*/
virtual int cmp_prefix(const uchar *a, const uchar *b, size_t prefix_len)
{ return cmp(a, b); }
virtual int cmp_binary(const uchar *a,const uchar *b, uint32 max_length=~0L)
{ return memcmp(a,b,pack_length()); }
virtual int cmp_offset(uint row_offset)
Expand Down Expand Up @@ -2991,11 +2995,8 @@ class Field_varstring :public Field_longstr {
longlong val_int(void);
String *val_str(String*,String *);
my_decimal *val_decimal(my_decimal *);
int cmp_max(const uchar *, const uchar *, uint max_length);
int cmp(const uchar *a,const uchar *b)
{
return cmp_max(a, b, ~0L);
}
int cmp(const uchar *a,const uchar *b);
int cmp_prefix(const uchar *a, const uchar *b, size_t prefix_len);
void sort_string(uchar *buff,uint length);
uint get_key_image(uchar *buff,uint length, imagetype type);
void set_key_image(const uchar *buff,uint length);
Expand Down Expand Up @@ -3077,9 +3078,8 @@ class Field_blob :public Field_longstr {
longlong val_int(void);
String *val_str(String*,String *);
my_decimal *val_decimal(my_decimal *);
int cmp_max(const uchar *, const uchar *, uint max_length);
int cmp(const uchar *a,const uchar *b)
{ return cmp_max(a, b, ~0L); }
int cmp(const uchar *a,const uchar *b);
int cmp_prefix(const uchar *a, const uchar *b, size_t prefix_len);
int cmp(const uchar *a, uint32 a_length, const uchar *b, uint32 b_length);
int cmp_binary(const uchar *a,const uchar *b, uint32 max_length=~0L);
int key_cmp(const uchar *,const uchar*);
Expand Down Expand Up @@ -3399,7 +3399,7 @@ class Field_bit :public Field {
}
int cmp_binary_offset(uint row_offset)
{ return cmp_offset(row_offset); }
int cmp_max(const uchar *a, const uchar *b, uint max_length);
int cmp_prefix(const uchar *a, const uchar *b, size_t prefix_len);
int key_cmp(const uchar *a, const uchar *b)
{ return cmp_binary((uchar *) a, (uchar *) b); }
int key_cmp(const uchar *str, uint length);
Expand Down
4 changes: 2 additions & 2 deletions sql/key.cc
View file
Expand Up @@ -623,8 +623,8 @@ int key_rec_cmp(void *key_p, uchar *first_rec, uchar *second_rec)
max length. The exceptions are the BLOB and VARCHAR field types
that take the max length into account.
*/
if ((result= field->cmp_max(field->ptr+first_diff, field->ptr+sec_diff,
key_part->length)))
if ((result= field->cmp_prefix(field->ptr+first_diff, field->ptr+sec_diff,
key_part->length)))
DBUG_RETURN(result);
next_loop:
key_part++;
Expand Down

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