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WL#1724 "Min/Max Optimization for Queries with Group By Clause"

- after-review changes
- merged with the source tree from 204-08-27
This commit is contained in:
timour@mysql.com
2004-08-27 16:37:13 +03:00
parent a5f063e0da
commit e2cd3dd1ce
19 changed files with 5077 additions and 204 deletions

View File

@ -146,7 +146,8 @@ public:
QS_TYPE_RANGE_DESC = 2,
QS_TYPE_FULLTEXT = 3,
QS_TYPE_ROR_INTERSECT = 4,
QS_TYPE_ROR_UNION = 5
QS_TYPE_ROR_UNION = 5,
QS_TYPE_GROUP_MIN_MAX = 6
};
/* Get type of this quick select - one of the QS_TYPE_* values */
@ -278,14 +279,12 @@ public:
int init();
int get_next();
void range_end();
int get_next_prefix(uint prefix_length, byte *cur_prefix);
bool reverse_sorted() { return 0; }
bool unique_key_range();
int init_ror_merged_scan(bool reuse_handler);
void save_last_pos()
{
file->position(record);
};
{ file->position(record); }
int get_type() { return QS_TYPE_RANGE; }
void add_keys_and_lengths(String *key_names, String *used_lengths);
void add_info_string(String *str);
@ -518,6 +517,103 @@ private:
};
/*
Index scan for GROUP-BY queries with MIN/MAX aggregate functions.
This class provides a specialized index access method for GROUP-BY queries
of the forms:
SELECT A_1,...,A_k, [B_1,...,B_m], [MIN(C)], [MAX(C)]
FROM T
WHERE [RNG(A_1,...,A_p ; where p <= k)]
[AND EQ(B_1,...,B_m)]
[AND PC(C)]
[AND PA(A_i1,...,A_iq)]
GROUP BY A_1,...,A_k;
or
SELECT DISTINCT A_i1,...,A_ik
FROM T
WHERE [RNG(A_1,...,A_p ; where p <= k)]
[AND PA(A_i1,...,A_iq)];
where all selected fields are parts of the same index.
The class of queries that can be processed by this quick select is fully
specified in the description of get_best_trp_group_min_max() in opt_range.cc.
The get_next() method directly produces result tuples, thus obviating the
need to call end_send_group() because all grouping is already done inside
get_next().
Since one of the requirements is that all select fields are part of the same
index, this class produces only index keys, and not complete records.
*/
class QUICK_GROUP_MIN_MAX_SELECT : public QUICK_SELECT_I
{
private:
handler *file; /* The handler used to get data. */
JOIN *join; /* Descriptor of the current query */
KEY *index_info; /* The index chosen for data access */
byte *record; /* Buffer where the next record is returned. */
byte *tmp_record; /* Temporary storage for next_min(), next_max(). */
byte *group_prefix; /* Key prefix consisting of the GROUP fields. */
uint group_prefix_len; /* Length of the group prefix. */
byte *last_prefix; /* Prefix of the last group for detecting EOF. */
bool have_min; /* Specify whether we are computing */
bool have_max; /* a MIN, a MAX, or both. */
bool seen_first_key; /* Denotes whether the first key was retrieved.*/
KEY_PART_INFO *min_max_arg_part; /* The keypart of the only argument field */
/* of all MIN/MAX functions. */
uint min_max_arg_len; /* The length of the MIN/MAX argument field */
byte *key_infix; /* Infix of constants from equality predicates. */
uint key_infix_len;
DYNAMIC_ARRAY min_max_ranges; /* Array of range ptrs for the MIN/MAX field. */
uint real_prefix_len; /* Length of key prefix extended with key_infix. */
List<Item_sum> *min_functions;
List<Item_sum> *max_functions;
List_iterator<Item_sum> *min_functions_it;
List_iterator<Item_sum> *max_functions_it;
public:
/*
The following two members are public to allow easy access from
TRP_GROUP_MIN_MAX::make_quick()
*/
MEM_ROOT alloc; /* Memory pool for this and quick_prefix_select data. */
QUICK_RANGE_SELECT *quick_prefix_select;/* For retrieval of group prefixes. */
private:
int next_prefix();
int next_min_in_range();
int next_max_in_range();
int next_min();
int next_max();
void update_min_result();
void update_max_result();
public:
QUICK_GROUP_MIN_MAX_SELECT(TABLE *table, JOIN *join, bool have_min,
bool have_max, KEY_PART_INFO *min_max_arg_part,
uint group_prefix_len, uint used_key_parts,
KEY *index_info, uint use_index, double read_cost,
ha_rows records, uint key_infix_len,
byte *key_infix, MEM_ROOT *parent_alloc);
~QUICK_GROUP_MIN_MAX_SELECT();
bool add_range(SEL_ARG *sel_range);
void update_key_stat();
bool alloc_buffers();
int init();
int reset();
int get_next();
bool reverse_sorted() { return false; }
bool unique_key_range() { return false; }
int get_type() { return QS_TYPE_GROUP_MIN_MAX; }
void add_keys_and_lengths(String *key_names, String *used_lengths);
#ifndef DBUG_OFF
void dbug_dump(int indent, bool verbose);
#endif
};
class QUICK_SELECT_DESC: public QUICK_RANGE_SELECT
{
public: