histogram.h File Reference

Histogram base class. More...

#include <cstddef>
#include <functional>
#include <map>
#include <memory>
#include <set>
#include <string>
#include <utility>
#include "lex_string.h"
#include "my_base.h"
#include "sql/field.h"
#include "sql/histograms/value_map_type.h"
#include "sql/mem_root_allocator.h"
#include "sql/stateless_allocator.h"

Go to the source code of this file.

Classes
struct	histograms::Histogram_psi_key_alloc
class	histograms::Error_context
	Error context to validate given JSON object which represents a histogram. More...
class	histograms::Histogram
	Histogram base class. More...
struct	histograms::HistogramSetting
	A simple struct containing the settings for a histogram to be built. More...

Namespaces
namespace	dd
	The version of the current data dictionary table definitions.
namespace	histograms

Typedefs
template<class T >
using	histograms::Histogram_key_allocator = Stateless_allocator< T, Histogram_psi_key_alloc >
template<class T >
using	histograms::value_map_allocator = Mem_root_allocator< std::pair< const T, ha_rows > >
template<typename T >
using	histograms::value_map_type = std::map< T, ha_rows, Histogram_comparator, value_map_allocator< T > >
using	histograms::columns_set = std::set< std::string, std::less< std::string >, Histogram_key_allocator< std::string > >
using	histograms::results_map = std::map< std::string, Message, std::less< std::string >, Histogram_key_allocator< std::pair< const std::string, Message > > >

Enumerations
enum class	histograms::Message {   histograms::FIELD_NOT_FOUND , histograms::UNSUPPORTED_DATA_TYPE , histograms::TEMPORARY_TABLE , histograms::ENCRYPTED_TABLE ,   histograms::VIEW , histograms::HISTOGRAM_CREATED , histograms::MULTIPLE_TABLES_SPECIFIED , histograms::COVERED_BY_SINGLE_PART_UNIQUE_INDEX ,   histograms::NO_HISTOGRAM_FOUND , histograms::HISTOGRAM_DELETED , histograms::SERVER_READ_ONLY , histograms::MULTIPLE_COLUMNS_SPECIFIED ,   histograms::SYSTEM_SCHEMA_NOT_SUPPORTED , histograms::JSON_FORMAT_ERROR , histograms::JSON_NOT_AN_OBJECT , histograms::JSON_MISSING_ATTRIBUTE ,   histograms::JSON_WRONG_ATTRIBUTE_TYPE , histograms::JSON_WRONG_BUCKET_TYPE_2 , histograms::JSON_WRONG_BUCKET_TYPE_4 , histograms::JSON_WRONG_DATA_TYPE ,   histograms::JSON_UNSUPPORTED_DATA_TYPE , histograms::JSON_UNSUPPORTED_HISTOGRAM_TYPE , histograms::JSON_UNSUPPORTED_CHARSET , histograms::JSON_INVALID_SAMPLING_RATE ,   histograms::JSON_INVALID_NUM_BUCKETS_SPECIFIED , histograms::JSON_INVALID_FREQUENCY , histograms::JSON_INVALID_NUM_DISTINCT , histograms::JSON_VALUE_FORMAT_ERROR ,   histograms::JSON_VALUE_OUT_OF_RANGE , histograms::JSON_VALUE_NOT_ASCENDING_1 , histograms::JSON_VALUE_NOT_ASCENDING_2 , histograms::JSON_VALUE_DESCENDING_IN_BUCKET ,   histograms::JSON_CUMULATIVE_FREQUENCY_NOT_ASCENDING , histograms::JSON_INVALID_NULL_VALUES_FRACTION , histograms::JSON_INVALID_TOTAL_FREQUENCY , histograms::JSON_NUM_BUCKETS_MORE_THAN_SPECIFIED ,   histograms::JSON_IMPOSSIBLE_EMPTY_EQUI_HEIGHT }
enum class	histograms::enum_operator {   histograms::EQUALS_TO , histograms::GREATER_THAN , histograms::LESS_THAN , histograms::IS_NULL ,   histograms::IS_NOT_NULL , histograms::LESS_THAN_OR_EQUAL , histograms::GREATER_THAN_OR_EQUAL , histograms::NOT_EQUALS_TO ,   histograms::BETWEEN , histograms::NOT_BETWEEN , histograms::IN_LIST , histograms::NOT_IN_LIST }
	The different operators we can ask histogram statistics for selectivity estimations. More...

Functions
bool	histograms::empty (const Histogram &histogram)
	Return true if 'histogram' was built on an empty table. More...
template<class T >
Histogram *	histograms::build_histogram (MEM_ROOT *mem_root, const Value_map< T > &value_map, size_t num_buckets, const std::string &db_name, const std::string &tbl_name, const std::string &col_name)
	Create a histogram from a value map. More...
bool	histograms::update_histograms (THD *thd, Table_ref *table, Mem_root_array< HistogramSetting > *settings, results_map &results)
	Create or update histograms for a set of columns of a given table. More...
bool	histograms::auto_update_table_histograms (THD *thd, Table_ref *table)
	Updates existing histograms on a table that were specified with the AUTO UPDATE option. More...
bool	histograms::update_share_histograms (THD *thd, Table_ref *table)
	Retrieve an updated snapshot of the histograms on a table directly from the dictionary (in an inefficient manner, querying all columns) and inserts this snapshot in the Table_histograms_collection on the TABLE_SHARE. More...
bool	histograms::auto_update_table_histograms_from_background_thread (THD *thd, const std::string &db_name, const std::string &table_name)
	Updates existing histograms on a table that were specified with the AUTO UPDATE option. More...
bool	histograms::drop_all_histograms (THD *thd, Table_ref &table, const dd::Table &original_table_def, results_map &results)
	Drop histograms for all columns in a given table. More...
bool	histograms::drop_histograms (THD *thd, Table_ref &table, const columns_set &columns, results_map &results)
	Drop histograms for a set of columns in a given table. More...
bool	histograms::rename_histograms (THD *thd, const char *old_schema_name, const char *old_table_name, const char *new_schema_name, const char *new_table_name, results_map &results)
	Rename histograms for all columns in a given table. More...
bool	histograms::find_histogram (THD *thd, const std::string &schema_name, const std::string &table_name, const std::string &column_name, const Histogram **histogram)

Variables
static const double	histograms::INVALID_NULL_VALUES_FRACTION = -1.0
	The default (and invalid) value for "m_null_values_fraction". More...

Detailed Description

Histogram base class.

This file defines the base class for all histogram types. We keep the base class itself non-templatized in order to more easily send a histogram as an argument, collect multiple histograms in a single collection etc.

A histogram is stored as a JSON object. This gives the flexibility of storing virtually an unlimited number of buckets, data values in its full length and easily expanding with new histogram types in the future. They are stored persistently in the system table mysql.column_stats.

We keep all histogram code in the namespace "histograms" in order to avoid name conflicts etc.