Current File : //usr/include/mysql/server/private/sql_statistics.h
/* Copyright 2006-2008 MySQL AB, 2008 Sun Microsystems, Inc.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1335 USA */
#ifndef SQL_STATISTICS_H
#define SQL_STATISTICS_H
/*
For COMPLEMENTARY_FOR_QUERIES and PREFERABLY_FOR_QUERIES they are
similar to the COMPLEMENTARY and PREFERABLY respectively except that
with these values we would not be collecting EITS for queries like
ANALYZE TABLE t1;
To collect EITS with these values, we have to use PERSISITENT FOR
analyze table t1 persistent for
columns (col1,col2...) index (idx1, idx2...)
or
analyze table t1 persistent for all
*/
typedef
enum enum_use_stat_tables_mode
{
NEVER,
COMPLEMENTARY,
PREFERABLY,
COMPLEMENTARY_FOR_QUERIES,
PREFERABLY_FOR_QUERIES
} Use_stat_tables_mode;
typedef
enum enum_histogram_type
{
SINGLE_PREC_HB,
DOUBLE_PREC_HB
} Histogram_type;
enum enum_stat_tables
{
TABLE_STAT,
COLUMN_STAT,
INDEX_STAT,
};
/*
These enumeration types comprise the dictionary of three
statistical tables table_stat, column_stat and index_stat
as they defined in ../scripts/mysql_system_tables.sql.
It would be nice if the declarations of these types were
generated automatically by the table definitions.
*/
enum enum_table_stat_col
{
TABLE_STAT_DB_NAME,
TABLE_STAT_TABLE_NAME,
TABLE_STAT_CARDINALITY,
TABLE_STAT_N_FIELDS
};
enum enum_column_stat_col
{
COLUMN_STAT_DB_NAME,
COLUMN_STAT_TABLE_NAME,
COLUMN_STAT_COLUMN_NAME,
COLUMN_STAT_MIN_VALUE,
COLUMN_STAT_MAX_VALUE,
COLUMN_STAT_NULLS_RATIO,
COLUMN_STAT_AVG_LENGTH,
COLUMN_STAT_AVG_FREQUENCY,
COLUMN_STAT_HIST_SIZE,
COLUMN_STAT_HIST_TYPE,
COLUMN_STAT_HISTOGRAM,
COLUMN_STAT_N_FIELDS
};
enum enum_index_stat_col
{
INDEX_STAT_DB_NAME,
INDEX_STAT_TABLE_NAME,
INDEX_STAT_INDEX_NAME,
INDEX_STAT_PREFIX_ARITY,
INDEX_STAT_AVG_FREQUENCY,
INDEX_STAT_N_FIELDS
};
inline
Use_stat_tables_mode get_use_stat_tables_mode(THD *thd)
{
return (Use_stat_tables_mode) (thd->variables.use_stat_tables);
}
inline
bool check_eits_collection_allowed(THD *thd)
{
return (get_use_stat_tables_mode(thd) == COMPLEMENTARY ||
get_use_stat_tables_mode(thd) == PREFERABLY);
}
inline
bool check_eits_preferred(THD *thd)
{
return (get_use_stat_tables_mode(thd) == PREFERABLY ||
get_use_stat_tables_mode(thd) == PREFERABLY_FOR_QUERIES);
}
int read_statistics_for_tables_if_needed(THD *thd, TABLE_LIST *tables);
int read_statistics_for_tables(THD *thd, TABLE_LIST *tables,
bool force_reload);
int collect_statistics_for_table(THD *thd, TABLE *table);
int alloc_statistics_for_table(THD *thd, TABLE *table, MY_BITMAP *stat_fields);
int update_statistics_for_table(THD *thd, TABLE *table);
int delete_statistics_for_table(THD *thd, const LEX_CSTRING *db,
const LEX_CSTRING *tab);
int delete_statistics_for_column(THD *thd, TABLE *tab, Field *col);
int delete_statistics_for_index(THD *thd, TABLE *tab, KEY *key_info,
bool ext_prefixes_only);
int rename_table_in_stat_tables(THD *thd, const LEX_CSTRING *db,
const LEX_CSTRING *tab,
const LEX_CSTRING *new_db,
const LEX_CSTRING *new_tab);
int rename_columns_in_stat_table(THD *thd, TABLE *tab,
List<Alter_info::RENAME_COLUMN_STAT_PARAMS> *fields);
int rename_indexes_in_stat_table(THD *thd, TABLE *tab,
List<Alter_info::RENAME_INDEX_STAT_PARAMS> *indexes);
void set_statistics_for_table(THD *thd, TABLE *table);
double get_column_avg_frequency(Field * field);
double get_column_range_cardinality(Field *field,
key_range *min_endp,
key_range *max_endp,
uint range_flag);
bool is_stat_table(const LEX_CSTRING *db, LEX_CSTRING *table);
bool is_eits_usable(Field* field);
class Histogram
{
private:
Histogram_type type;
uint8 size; /* Size of values array, in bytes */
uchar *values;
uint prec_factor()
{
switch (type) {
case SINGLE_PREC_HB:
return ((uint) (1 << 8) - 1);
case DOUBLE_PREC_HB:
return ((uint) (1 << 16) - 1);
}
return 1;
}
public:
uint get_width()
{
switch (type) {
case SINGLE_PREC_HB:
return size;
case DOUBLE_PREC_HB:
return size / 2;
}
return 0;
}
private:
uint get_value(uint i)
{
DBUG_ASSERT(i < get_width());
switch (type) {
case SINGLE_PREC_HB:
return (uint) (((uint8 *) values)[i]);
case DOUBLE_PREC_HB:
return (uint) uint2korr(values + i * 2);
}
return 0;
}
/* Find the bucket which value 'pos' falls into. */
uint find_bucket(double pos, bool first)
{
uint val= (uint) (pos * prec_factor());
int lp= 0;
int rp= get_width() - 1;
int d= get_width() / 2;
uint i= lp + d;
for ( ; d; d= (rp - lp) / 2, i= lp + d)
{
if (val == get_value(i))
break;
if (val < get_value(i))
rp= i;
else if (val > get_value(i + 1))
lp= i + 1;
else
break;
}
if (val > get_value(i) && i < (get_width() - 1))
i++;
if (val == get_value(i))
{
if (first)
{
while(i && val == get_value(i - 1))
i--;
}
else
{
while(i + 1 < get_width() && val == get_value(i + 1))
i++;
}
}
return i;
}
public:
uint get_size() { return (uint) size; }
Histogram_type get_type() { return type; }
uchar *get_values() { return (uchar *) values; }
void set_size (ulonglong sz) { size= (uint8) sz; }
void set_type (Histogram_type t) { type= t; }
void set_values (uchar *vals) { values= (uchar *) vals; }
bool is_available() { return get_size() > 0 && get_values(); }
/*
This function checks that histograms should be usable only when
1) the level of optimizer_use_condition_selectivity > 3
2) histograms have been collected
*/
bool is_usable(THD *thd)
{
return thd->variables.optimizer_use_condition_selectivity > 3 &&
is_available();
}
void set_value(uint i, double val)
{
switch (type) {
case SINGLE_PREC_HB:
((uint8 *) values)[i]= (uint8) (val * prec_factor());
return;
case DOUBLE_PREC_HB:
int2store(values + i * 2, val * prec_factor());
return;
}
}
void set_prev_value(uint i)
{
switch (type) {
case SINGLE_PREC_HB:
((uint8 *) values)[i]= ((uint8 *) values)[i-1];
return;
case DOUBLE_PREC_HB:
int2store(values + i * 2, uint2korr(values + i * 2 - 2));
return;
}
}
double range_selectivity(double min_pos, double max_pos)
{
double sel;
double bucket_sel= 1.0/(get_width() + 1);
uint min= find_bucket(min_pos, TRUE);
uint max= find_bucket(max_pos, FALSE);
sel= bucket_sel * (max - min + 1);
return sel;
}
/*
Estimate selectivity of "col=const" using a histogram
*/
double point_selectivity(double pos, double avg_sel);
};
class Columns_statistics;
class Index_statistics;
/* Statistical data on a table */
class Table_statistics
{
public:
my_bool cardinality_is_null; /* TRUE if the cardinality is unknown */
ha_rows cardinality; /* Number of rows in the table */
uchar *min_max_record_buffers; /* Record buffers for min/max values */
Column_statistics *column_stats; /* Array of statistical data for columns */
Index_statistics *index_stats; /* Array of statistical data for indexes */
/* Array of records per key for index prefixes */
ulonglong *idx_avg_frequency;
uchar *histograms; /* Sequence of histograms */
};
/*
Statistical data on a column
Note: objects of this class may be "empty", where they have almost all fields
as zeros, for example, get_avg_frequency() will return 0.
objects are allocated in alloc_statistics_for_table[_share].
*/
class Column_statistics
{
private:
static const uint Scale_factor_nulls_ratio= 100000;
static const uint Scale_factor_avg_length= 100000;
static const uint Scale_factor_avg_frequency= 100000;
public:
/*
Bitmap indicating what statistical characteristics
are available for the column
*/
uint32 column_stat_nulls;
/* For the below two, see comments in get_column_range_cardinality() */
/* Minimum value for the column */
Field *min_value;
/* Maximum value for the column */
Field *max_value;
private:
/*
The ratio Z/N multiplied by the scale factor Scale_factor_nulls_ratio,
where
N is the total number of rows,
Z is the number of nulls in the column
*/
ulong nulls_ratio;
/*
Average number of bytes occupied by the representation of a
value of the column in memory buffers such as join buffer
multiplied by the scale factor Scale_factor_avg_length.
CHAR values are stripped of trailing spaces.
Flexible values are stripped of their length prefixes.
*/
ulonglong avg_length;
/*
The ratio N/D multiplied by the scale factor Scale_factor_avg_frequency,
where
N is the number of rows with not null value in the column,
D the number of distinct values among them
*/
ulonglong avg_frequency;
public:
Histogram histogram;
uint32 no_values_provided_bitmap()
{
return
((1 << (COLUMN_STAT_HISTOGRAM-COLUMN_STAT_COLUMN_NAME))-1) <<
(COLUMN_STAT_COLUMN_NAME+1);
}
void set_all_nulls()
{
column_stat_nulls= no_values_provided_bitmap();
}
void set_not_null(uint stat_field_no)
{
column_stat_nulls&= ~(1 << stat_field_no);
}
bool is_null(uint stat_field_no)
{
return MY_TEST(column_stat_nulls & (1 << stat_field_no));
}
double get_nulls_ratio()
{
return (double) nulls_ratio / Scale_factor_nulls_ratio;
}
double get_avg_length()
{
return (double) avg_length / Scale_factor_avg_length;
}
double get_avg_frequency()
{
return (double) avg_frequency / Scale_factor_avg_frequency;
}
void set_nulls_ratio (double val)
{
nulls_ratio= (ulong) (val * Scale_factor_nulls_ratio);
}
void set_avg_length (double val)
{
avg_length= (ulonglong) (val * Scale_factor_avg_length);
}
void set_avg_frequency (double val)
{
avg_frequency= (ulonglong) (val * Scale_factor_avg_frequency);
}
bool min_max_values_are_provided()
{
return !is_null(COLUMN_STAT_MIN_VALUE) &&
!is_null(COLUMN_STAT_MAX_VALUE);
}
/*
This function checks whether the values for the fields of the statistical
tables that were NULL by DEFAULT for a column have changed or not.
@retval
TRUE: Statistics are not present for a column
FALSE: Statisitics are present for a column
*/
bool no_stat_values_provided()
{
return (column_stat_nulls == no_values_provided_bitmap());
}
};
/* Statistical data on an index prefixes */
class Index_statistics
{
private:
static const uint Scale_factor_avg_frequency= 100000;
/*
The k-th element of this array contains the ratio N/D
multiplied by the scale factor Scale_factor_avg_frequency,
where N is the number of index entries without nulls
in the first k components, and D is the number of distinct
k-component prefixes among them
*/
ulonglong *avg_frequency;
public:
void init_avg_frequency(ulonglong *ptr) { avg_frequency= ptr; }
bool avg_frequency_is_inited() { return avg_frequency != NULL; }
double get_avg_frequency(uint i)
{
return (double) avg_frequency[i] / Scale_factor_avg_frequency;
}
void set_avg_frequency(uint i, double val)
{
avg_frequency[i]= (ulonglong) (val * Scale_factor_avg_frequency);
}
};
#endif /* SQL_STATISTICS_H */
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