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MDEV-20057 Distinct SUM on CROSS JOIN and grouped returns wrong result

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SELECT DISTINCT did not work with expressions with sum functions.
Distinct was only done on the values stored in the intermediate temporary
tables, which only stored the value of each sum function.

In other words:
SELECT DISTINCT sum(a),sum(b),avg(c) ... worked.
SELECT DISTINCT sum(a),sum(b) > 2,sum(c)+sum(d) would not work.

The later query would do ONLY apply distinct on the sum(a) part.

Reviewer: Sergei Petrunia <sergey@mariadb.com>


This was fixed by extending remove_dup_with_hash_index() and
remove_dup_with_compare() to take into account the columns in the result
list that where not stored in the temporary table.

Note that in many cases the above dup removal functions are not used as
the optimizer may be able to either remove duplicates early or it will
discover that duplicate remove is not needed. The later happens for
example if the group by fields is part of the result.

Other things:
- Backported from 11.0 the change of Sort_param.tmp_buffer from char* to
  String.
- Changed Type_handler::make_sort_key() to take String as a parameter
  instead of Sort_param. This was done to allow make_sort_key() functions
  to be reused by distinct elimination functions.
  This makes Type_handler_string_result::make_sort_key() similar to code
  in 11.0
- Simplied error handling in remove_dup_with_compare() to remove code
  duplication.
This commit is contained in:
Monty
2023-02-16 14:19:33 +02:00
parent bd0d7ea540
commit 476b24d084
6 changed files with 245 additions and 74 deletions
Download Patch File Download Diff File Expand all files Collapse all files

16
sql/sql_type.h
View File

@ -3734,7 +3734,7 @@ public:
virtual void make_sort_key(uchar *to, Item *item,
const SORT_FIELD_ATTR *sort_field,
Sort_param *param) const= 0;
String *tmp) const= 0;
virtual void sortlength(THD *thd,
const Type_std_attributes *item,
SORT_FIELD_ATTR *attr) const= 0;
@ -4120,7 +4120,7 @@ public:
const Bit_addr &bit,
const Column_definition_attributes *attr,
uint32 flags) const override;
void make_sort_key(uchar *, Item *, const SORT_FIELD_ATTR *, Sort_param *)
void make_sort_key(uchar *, Item *, const SORT_FIELD_ATTR *, String *tmp)
const override
{
MY_ASSERT_UNREACHABLE();
@ -4431,7 +4431,7 @@ public:
const Item *outer,
bool is_in_predicate) const;
void make_sort_key(uchar *to, Item *item, const SORT_FIELD_ATTR *sort_field,
Sort_param *param) const;
String *tmp) const;
void sortlength(THD *thd,
const Type_std_attributes *item,
SORT_FIELD_ATTR *attr) const;
@ -4519,7 +4519,7 @@ public:
bool is_in_predicate) const;
Field *make_num_distinct_aggregator_field(MEM_ROOT *, const Item *) const;
void make_sort_key(uchar *to, Item *item, const SORT_FIELD_ATTR *sort_field,
Sort_param *param) const;
String *tmp) const;
void sortlength(THD *thd,
const Type_std_attributes *item,
SORT_FIELD_ATTR *attr) const;
@ -4745,7 +4745,7 @@ public:
bool is_in_predicate) const;
Field *make_num_distinct_aggregator_field(MEM_ROOT *, const Item *) const;
void make_sort_key(uchar *to, Item *item, const SORT_FIELD_ATTR *sort_field,
Sort_param *param) const;
String *tmp) const;
void sortlength(THD *thd,
const Type_std_attributes *item,
SORT_FIELD_ATTR *attr) const;
@ -4834,7 +4834,7 @@ public:
Item_result cmp_type() const { return TIME_RESULT; }
virtual ~Type_handler_temporal_result() = default;
void make_sort_key(uchar *to, Item *item, const SORT_FIELD_ATTR *sort_field,
Sort_param *param) const;
String *tmp) const;
void sortlength(THD *thd,
const Type_std_attributes *item,
SORT_FIELD_ATTR *attr) const;
@ -4921,7 +4921,7 @@ public:
type_handler_adjusted_to_max_octet_length(uint max_octet_length,
CHARSET_INFO *cs) const;
void make_sort_key(uchar *to, Item *item, const SORT_FIELD_ATTR *sort_field,
Sort_param *param) const;
String *tmp) const;
void sortlength(THD *thd,
const Type_std_attributes *item,
SORT_FIELD_ATTR *attr) const;
@ -5953,7 +5953,7 @@ public:
cmp_item *make_cmp_item(THD *thd, CHARSET_INFO *cs) const;
in_vector *make_in_vector(THD *thd, const Item_func_in *f, uint nargs) const;
void make_sort_key(uchar *to, Item *item, const SORT_FIELD_ATTR *sort_field,
Sort_param *param) const;
String *tmp) const;
void sortlength(THD *thd,
const Type_std_attributes *item,
SORT_FIELD_ATTR *attr) const;