column_statistics.h

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/* Copyright (c) 2017, 2024, Oracle and/or its affiliates.
 
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   it under the terms of the GNU General Public License, version 2.0,
   as published by the Free Software Foundation.
 
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   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA */
 
#ifndef DD__COLUMN_STATISTIC_INCLUDED
#define DD__COLUMN_STATISTIC_INCLUDED
 
#include "my_alloc.h"                    // MEM_ROOT
#include "sql/dd/sdi_fwd.h"              // RJ_Document
#include "sql/dd/types/entity_object.h"  // dd::Entity_object
 
class THD;
struct MDL_key;
 
namespace histograms {
class Histogram;
}
 
namespace dd {
 
///////////////////////////////////////////////////////////////////////////
 
class Column_statistics_impl;
class Item_name_key;
class Primary_id_key;
class Void_key;
 
namespace tables {
class Column_statistics;
}
 
///////////////////////////////////////////////////////////////////////////
 
class Column_statistics : virtual public Entity_object {
 protected:
  /// MEM_ROOT on which the histogram data is allocated.
  MEM_ROOT m_mem_root;
 
 public:
  typedef Column_statistics_impl Impl;
  typedef Column_statistics Cache_partition;
  typedef tables::Column_statistics DD_table;
  typedef Primary_id_key Id_key;
  typedef Item_name_key Name_key;
  typedef Void_key Aux_key;
 
  // We need a set of functions to update a preallocated key.
  bool update_id_key(Id_key *key) const { return update_id_key(key, id()); }
 
  static bool update_id_key(Id_key *key, Object_id id);
 
  bool update_name_key(Name_key *key) const {
    return update_name_key(key, name());
  }
 
  static bool update_name_key(Name_key *key, const String_type &name);
 
  bool update_aux_key(Aux_key *) const { return true; }
 
  ~Column_statistics() override = default;
 
  virtual const String_type &schema_name() const = 0;
  virtual void set_schema_name(const String_type &schema_name) = 0;
 
  virtual const String_type &table_name() const = 0;
  virtual void set_table_name(const String_type &table_name) = 0;
 
  virtual const String_type &column_name() const = 0;
  virtual void set_column_name(const String_type &column_name) = 0;
 
  virtual const histograms::Histogram *histogram() const = 0;
  virtual void set_histogram(const histograms::Histogram *histogram) = 0;
 
  /**
    Converts *this into json.
 
    Converts all member variables that are to be included in the sdi
    into json by transforming them appropriately and passing them to
    the rapidjson writer provided.
 
    @param wctx opaque context for data needed by serialization
    @param w rapidjson writer which will perform conversion to json
 
  */
  virtual void serialize(Sdi_wcontext *wctx, Sdi_writer *w) const = 0;
 
  /**
    Re-establishes the state of *this by reading sdi information from
    the rapidjson DOM subobject provided.
 
    Cross-references encountered within this object are tracked in
    sdictx, so that they can be updated when the entire object graph
    has been established.
 
    @param rctx stores book-keeping information for the
    deserialization process
    @param val subobject of rapidjson DOM containing json
    representation of this object
  */
  virtual bool deserialize(Sdi_rcontext *rctx, const RJ_Value &val) = 0;
 
  /*
    Create a unique name for a column statistic object based on the triplet
    SCHEMA_NAME TABLE_NAME COLUMN_NAME separated with the 'Unit Separator'
    character.
  */
  static String_type create_name(const String_type &schema_name,
                                 const String_type &table_name,
                                 const String_type &column_name);
 
  String_type create_name() const {
    return Column_statistics::create_name(schema_name(), table_name(),
                                          column_name());
  }
 
  static void create_mdl_key(const String_type &schema_name,
                             const String_type &table_name,
                             const String_type &column_name, MDL_key *key);
 
  void create_mdl_key(MDL_key *key) const {
    Column_statistics::create_mdl_key(schema_name(), table_name(),
                                      column_name(), key);
  }
 
  virtual Column_statistics *clone() const = 0;
 
  /**
    Allocate a new object which can serve as a placeholder for the original
    object in the Dictionary_client's dropped registry. Such object has the
    same keys as the original but has no other info and as result occupies
    less memory.
  */
  virtual Column_statistics *clone_dropped_object_placeholder() const = 0;
};
 
///////////////////////////////////////////////////////////////////////////
 
}  // namespace dd
 
#endif  // DD__COLUMN_STATISTIC_INCLUDED