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Split histogram classes and into JSON and binary classes

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Signed-off-by: Michael Okoko <okokomichaels@outlook.com>
This commit is contained in:
Michael Okoko 2021-07-28 05:19:06 +01:00 committed by Sergei Petrunia
parent 1998b787ac
commit 1fa7af749e
2 changed files with 132 additions and 39 deletions
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79
sql/sql_statistics.cc
View File

@ -76,6 +76,8 @@ std::vector<std::string> parse_histogram_from_json(const char *json);
void test_parse_histogram_from_json();
Histogram_base *create_histogram(Histogram_type hist_type);
/* Currently there are only 3 persistent statistical tables */
static const uint STATISTICS_TABLES= 3;
@ -1217,9 +1219,9 @@ public:
The method assumes that the value of histogram size and the pointer to
the histogram location has been already set in the fields size and values
of read_stats->histogram.
*/
*/
Histogram * load_histogram(MEM_ROOT *mem_root)
Histogram_binary * load_histogram(MEM_ROOT *mem_root)
{
if (find_stat())
{
@ -1230,7 +1232,7 @@ public:
table_field->read_stats->set_not_null(fldno);
stat_field->val_str(&val);
// histogram-todo: here, create the histogram of appropriate type.
Histogram *hist= new (mem_root) Histogram();
Histogram_binary *hist= new (mem_root) Histogram_binary();
if (!hist->parse(mem_root, table_field->read_stats->histogram_type_on_disk,
(const uchar*)val.ptr(), val.length()))
{
@ -1244,7 +1246,7 @@ public:
}
};
bool Histogram::parse(MEM_ROOT *mem_root, Histogram_type type_arg, const uchar *ptr_arg, uint size_arg)
bool Histogram_binary::parse(MEM_ROOT *mem_root, Histogram_type type_arg, const uchar *ptr_arg, uint size_arg)
{
// Just copy the data
size = (uint8) size_arg;
@ -1258,7 +1260,7 @@ bool Histogram::parse(MEM_ROOT *mem_root, Histogram_type type_arg, const uchar *
/*
Save the histogram data info a table field.
*/
void Histogram::serialize(Field *field)
void Histogram_binary::serialize(Field *field)
{
if (get_type() == JSON)
{
@ -1269,7 +1271,7 @@ void Histogram::serialize(Field *field)
field->store((char*)get_values(), get_size(), &my_charset_bin);
}
void Histogram::init_for_collection(MEM_ROOT *mem_root,
void Histogram_binary::init_for_collection(MEM_ROOT *mem_root,
Histogram_type htype_arg,
ulonglong size_arg)
{
@ -1278,6 +1280,13 @@ void Histogram::init_for_collection(MEM_ROOT *mem_root,
size= (uint8) size_arg;
}
void Histogram_json::init_for_collection(MEM_ROOT *mem_root, Histogram_type htype_arg, ulonglong size_arg)
{
type= htype_arg;
values = (uchar*)alloc_root(mem_root, size_arg);
size = (uint8) size_arg;
}
/*
An object of the class Index_stat is created to read statistical
data on tables from the statistical table table_stat, to update
@ -1595,13 +1604,13 @@ public:
class Histogram_builder
{
protected:
private:
Field *column; /* table field for which the histogram is built */
uint col_length; /* size of this field */
ha_rows records; /* number of records the histogram is built for */
Field *min_value; /* pointer to the minimal value for the field */
Field *max_value; /* pointer to the maximal value for the field */
Histogram *histogram; /* the histogram location */
Histogram_binary *histogram; /* the histogram location */
uint hist_width; /* the number of points in the histogram */
double bucket_capacity; /* number of rows in a bucket of the histogram */
uint curr_bucket; /* number of the current bucket to be built */
@ -1617,7 +1626,7 @@ public:
Column_statistics *col_stats= col->collected_stats;
min_value= col_stats->min_value;
max_value= col_stats->max_value;
histogram= col_stats->histogram_;
histogram= dynamic_cast<Histogram_binary *>(col_stats->histogram_);
hist_width= histogram->get_width();
bucket_capacity= (double) records / (hist_width + 1);
curr_bucket= 0;
@ -1626,6 +1635,8 @@ public:
count_distinct_single_occurence= 0;
}
Histogram_builder() = default;
virtual ~Histogram_builder() = default;
ulonglong get_count_distinct() const { return count_distinct; }
@ -1661,16 +1672,29 @@ public:
class Histogram_builder_json : public Histogram_builder
{
std::vector<std::string> bucket_bounds = {};
Field *column; /* table field for which the histogram is built */
uint col_length; /* size of this field */
ha_rows records; /* number of records the histogram is built for */
Field *min_value; /* pointer to the minimal value for the field */
Field *max_value; /* pointer to the maximal value for the field */
Histogram_json *histogram; /* the histogram location */
uint hist_width; /* the number of points in the histogram */
double bucket_capacity; /* number of rows in a bucket of the histogram */
uint curr_bucket; /* number of the current bucket to be built */
ulonglong count; /* number of values retrieved */
ulonglong count_distinct; /* number of distinct values retrieved */
/* number of distinct values that occured only once */
ulonglong count_distinct_single_occurence;
std::vector<std::string> bucket_bounds = {};
public:
Histogram_builder_json(Field *col, uint col_len, ha_rows rows)
: Histogram_builder(col, col_len, rows)
: column(col), col_length(col_len), records(rows)
{
Column_statistics *col_stats= col->collected_stats;
min_value= col_stats->min_value;
max_value= col_stats->max_value;
histogram= col_stats->histogram_;
histogram= dynamic_cast<Histogram_json *>(col_stats->histogram_);
hist_width= histogram->get_width();
bucket_capacity= (double) records / (hist_width + 1);
curr_bucket= 0;
@ -1718,6 +1742,15 @@ public:
}
};
Histogram_base *create_histogram(Histogram_type hist_type)
{
// assumes the caller already checked for invalid histograms
if (hist_type == JSON)
return new Histogram_json;
else
return new Histogram_binary;
}
void test_parse_histogram_from_json()
{
std::vector<std::string> bucket = {};
@ -1954,9 +1987,9 @@ public:
@brief
Get the pointer to the histogram built for table_field
*/
Histogram *get_histogram()
Histogram_binary *get_histogram()
{
return table_field->collected_stats->histogram_;
return dynamic_cast<Histogram_binary *>(table_field->collected_stats->histogram_);
}
};
@ -2608,18 +2641,18 @@ bool Column_statistics_collected::add()
/*
Create an empty Histogram object from histogram_type.
Create an empty Histogram_binary object from histogram_type.
Note: it is not yet clear whether collection-time histogram should be the same
as lookup-time histogram. At the moment, they are.
*/
Histogram* get_histogram_by_type(MEM_ROOT *mem_root, Histogram_type hist_type) {
Histogram_binary * get_histogram_by_type(MEM_ROOT *mem_root, Histogram_type hist_type) {
switch (hist_type) {
case SINGLE_PREC_HB:
case DOUBLE_PREC_HB:
case JSON:
return new Histogram();
return new Histogram_binary();
default:
DBUG_ASSERT(0);
}
@ -2660,7 +2693,7 @@ void Column_statistics_collected::finish(MEM_ROOT *mem_root, ha_rows rows, doubl
if (hist_size != 0 && hist_type != INVALID_HISTOGRAM)
{
have_histogram= true;
histogram_= new Histogram;
histogram_= create_histogram(hist_type);
histogram_->init_for_collection(mem_root, hist_type, hist_size);
}
@ -4048,7 +4081,8 @@ double get_column_range_cardinality(Field *field,
if (avg_frequency > 1.0 + 0.000001 &&
col_stats->min_max_values_are_provided())
{
Histogram *hist= col_stats->histogram_;
Histogram_binary *hist=
dynamic_cast<Histogram_binary *>(col_stats->histogram_);
if (hist && hist->is_usable(thd))
{
store_key_image_to_rec(field, (uchar *) min_endp->key,
@ -4092,7 +4126,8 @@ double get_column_range_cardinality(Field *field,
else
max_mp_pos= 1.0;
Histogram *hist= col_stats->histogram_;
Histogram_binary *hist=
dynamic_cast<Histogram_binary *>(col_stats->histogram_);
if (hist && hist->is_usable(thd))
sel= hist->range_selectivity(min_mp_pos, max_mp_pos);
else
@ -4143,7 +4178,7 @@ double get_column_range_cardinality(Field *field,
value.
*/
double Histogram::point_selectivity(double pos, double avg_sel)
double Histogram_binary::point_selectivity(double pos, double avg_sel)
{
double sel;
/* Find the bucket that contains the value 'pos'. */
@ -4179,7 +4214,7 @@ double Histogram::point_selectivity(double pos, double avg_sel)
/*
The value 'pos' fits within one single histogram bucket.
Histogram buckets have the same numbers of rows, but they cover
Histogram_binary buckets have the same numbers of rows, but they cover
different ranges of values.
We assume that values are uniformly distributed across the [0..1] value

92
sql/sql_statistics.h
View File

@ -153,6 +153,24 @@ public:
virtual void serialize(Field *to_field)= 0;
virtual Histogram_type get_type()=0;
virtual uint get_width()=0;
virtual void init_for_collection(MEM_ROOT *mem_root, Histogram_type htype_arg, ulonglong size)=0;
virtual bool is_available()=0;
virtual bool is_usable(THD *thd)=0;
virtual void set_values(uchar * values)=0;
virtual uchar *get_values()=0;
virtual void set_size(ulonglong sz)=0;
virtual double range_selectivity(double min_pos, double max_pos)=0;
virtual double point_selectivity(double pos, double avg_selection)=0;
// Legacy: return the size of the histogram on disk.
// This will be stored in mysql.column_stats.hist_size column.
@ -162,22 +180,21 @@ public:
virtual ~Histogram_base(){}
};
class Histogram : public Histogram_base
class Histogram_binary : public Histogram_base
{
public:
bool parse(MEM_ROOT *mem_root, Histogram_type type_arg,
const uchar *ptr_arg, uint size_arg) override;
void serialize(Field *to_field) override;
Histogram_type get_type() override { return type; }
uint get_size() override { return (uint) size; }
// returns number of buckets in the histogram
uint get_width()
uint get_width() override
{
switch (type) {
case SINGLE_PREC_HB:
case JSON:
return size;
case DOUBLE_PREC_HB:
return size / 2;
@ -196,7 +213,6 @@ private:
{
switch (type) {
case SINGLE_PREC_HB:
case JSON:
return ((uint) (1 << 8) - 1);
case DOUBLE_PREC_HB:
return ((uint) (1 << 16) - 1);
@ -211,7 +227,6 @@ private:
DBUG_ASSERT(i < get_width());
switch (type) {
case SINGLE_PREC_HB:
case JSON:
return (uint) (((uint8 *) values)[i]);
case DOUBLE_PREC_HB:
return (uint) uint2korr(values + i * 2);
@ -260,22 +275,22 @@ private:
return i;
}
uchar *get_values() { return (uchar *) values; }
uchar *get_values() override { return (uchar *) values; }
public:
void init_for_collection(MEM_ROOT *mem_root, Histogram_type htype_arg, ulonglong size);
void init_for_collection(MEM_ROOT *mem_root, Histogram_type htype_arg, ulonglong size) override;
// Note: these two are used only for saving the JSON text:
void set_values (uchar *vals) { values= (uchar *) vals; }
void set_size (ulonglong sz) { size= (uint8) sz; }
void set_values (uchar *vals) override { values= (uchar *) vals; }
void set_size (ulonglong sz) override { size= (uint8) sz; }
bool is_available() { return get_size() > 0 && get_values(); }
bool is_available() override { 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)
bool is_usable(THD *thd) override
{
return thd->variables.optimizer_use_condition_selectivity > 3 &&
is_available();
@ -285,7 +300,6 @@ public:
{
switch (type) {
case SINGLE_PREC_HB:
case JSON:
((uint8 *) values)[i]= (uint8) (val * prec_factor());
return;
case DOUBLE_PREC_HB:
@ -301,7 +315,6 @@ public:
{
switch (type) {
case SINGLE_PREC_HB:
case JSON:
((uint8 *) values)[i]= ((uint8 *) values)[i-1];
return;
case DOUBLE_PREC_HB:
@ -313,7 +326,7 @@ public:
}
}
double range_selectivity(double min_pos, double max_pos)
double range_selectivity(double min_pos, double max_pos) override
{
double sel;
double bucket_sel= 1.0/(get_width() + 1);
@ -326,9 +339,54 @@ public:
/*
Estimate selectivity of "col=const" using a histogram
*/
double point_selectivity(double pos, double avg_sel);
double point_selectivity(double pos, double avg_sel) override;
};
class Histogram_json : public Histogram_base
{
private:
Histogram_type type;
uint8 size; /* Number of elements in the histogram*/
uchar *values;
public:
bool parse(MEM_ROOT *mem_root, Histogram_type type_arg, const uchar *ptr, uint size) override {return false;}
void serialize(Field *to_field) override{}
uint get_size() override {return (uint) size;}
// returns number of buckets in the histogram
uint get_width() override
{
return size;
};
Histogram_type get_type() override
{
return JSON;
}
void set_size (ulonglong sz) override {size = (uint8) sz; }
void init_for_collection(MEM_ROOT *mem_root, Histogram_type htype_arg, ulonglong size) override;
bool is_available() override {return get_size() > 0 && get_values(); }
bool is_usable(THD *thd) override
{
return thd->variables.optimizer_use_condition_selectivity > 3 &&
is_available();
}
void set_values (uchar *vals) override { values= (uchar *) vals; }
uchar *get_values() override { return (uchar *) values; }
double range_selectivity(double min_pos, double max_pos) override {return 0.1;}
double point_selectivity(double pos, double avg_selection) override {return 0.5;}
};
class Columns_statistics;
class Index_statistics;
@ -411,7 +469,7 @@ private:
public:
Histogram_type histogram_type_on_disk;
Histogram *histogram_;
Histogram_base *histogram_;
uint32 no_values_provided_bitmap()
{