File statistics.h¶

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/*
 * Copyright 2008 Search Solution Corporation
 * Copyright 2016 CUBRID Corporation
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 */


/*
 * STATISTICS.h -
 */

#ifndef _STATISTICS_H_
#define _STATISTICS_H_

#ident "$Id$"

#include <stdio.h>
#include "dbtype_def.h"
#include "storage_common.h"
#include "object_domain.h"

#define STATS_WITH_FULLSCAN  true
#define STATS_WITH_SAMPLING  false

#define STATS_SAMPLING_THRESHOLD 5000   /* sampling trial count */
#define STATS_SAMPLING_LEAFS_MAX 5000   /* sampling leaf pages */
#define NUMBER_OF_SAMPLING_PAGES 5000
#define EXPECTED_ROWS_PER_PAGE 20

/* disk-resident elements of pkeys[] field */
#define BTREE_STATS_PKEYS_NUM      8
#define BTREE_STATS_RESERVED_NUM   4

#define STATS_MIN_MAX_SIZE    sizeof(DB_DATA)

#define STATS_MAX_PRECISION 4000    /* max precision of char for getting statistics */

/* free_and_init routine */
#define stats_free_statistics_and_init(stats) \
  do \
    { \
      stats_free_statistics ((stats)); \
      (stats) = NULL; \
    } \
  while (0)

/* B+tree statistical information */
typedef struct btree_stats BTREE_STATS;
struct btree_stats
{
  BTID btid;
  int leafs;            /* number of leaf pages including overflow pages */
  int pages;            /* number of total pages */
  int height;           /* the height of the B+tree */
  int keys;         /* number of keys */
  int has_function;     /* is a function index */
  TP_DOMAIN *key_type;      /* The key type for the B+tree */
  int pkeys_size;       /* pkeys array size */
  int *pkeys;           /* partial keys info for example: index (a, b, ..., x) pkeys[0] -> # of {a} pkeys[1] ->
                 * # of {a, b} ... pkeys[pkeys_size-1] -> # of {a, b, ..., x} */
  int dedup_idx;        /* support for SUPPORT_DEDUPLICATE_KEY_MODE */

#if 0               /* reserved for future use */
  int reserved[BTREE_STATS_RESERVED_NUM];
#endif
};

/* Statistical Information about the attribute */
typedef struct attr_stats ATTR_STATS;
struct attr_stats
{
  int id;
  DB_TYPE type;
  int n_btstats;        /* number of B+tree statistics information */
  BTREE_STATS *bt_stats;    /* pointer to array of BTREE_STATS[n_btstats] */
  INT64 ndv;            /* Number of Distinct Values of column */
};

/* Statistical Information about the class */
typedef struct class_stats CLASS_STATS;
struct class_stats
{
  unsigned int time_stamp;  /* the time stamped when the stat info updated; used to get up-to-date stat info */
  int heap_num_objects;     /* cardinality of the class; number of instances the class has */
  int heap_num_pages;       /* number of pages the class occupy */
  int n_attrs;          /* number of attributes; size of the attr_stats[] */
  ATTR_STATS *attr_stats;   /* pointer to the array of attribute statistics */
};

/* Statistical Information about the attribute NDV */
typedef struct attr_ndv ATTR_NDV;
struct attr_ndv
{
  int id;           /* column id */
  INT64 ndv;            /* Number of Distinct Values of column */
};

typedef struct class_attr_ndv CLASS_ATTR_NDV;
struct class_attr_ndv
{
  int attr_cnt;         /* column id */
  ATTR_NDV *attr_ndv;       /* Number of Distinct Values of column */
};
#define CLASS_ATTR_NDV_INITIALIZER  {0, NULL}

#if !defined(SERVER_MODE)
extern int stats_get_statistics (OID * classoid, unsigned int timestamp, CLASS_STATS ** stats_p);
extern void stats_free_statistics (CLASS_STATS * stats);
extern void stats_dump (const char *classname, FILE * fp);
extern void stats_ndv_dump (const char *classname, FILE * fp);
extern char *stats_make_select_list_for_ndv (const MOP class_mop, ATTR_NDV ** attr_ndv);
extern int stats_get_ndv_by_query (const MOP class_mop, CLASS_ATTR_NDV * class_attr_ndv, FILE * file_p,
                   int with_fullscan);
#endif /* !SERVER_MODE */
STATIC_INLINE int stats_adjust_sampling_weight (INT64 sampling_ndv, int sampling_weight)
  __attribute__ ((ALWAYS_INLINE));

/*
 * stats_adjust_sampling_weight () - adjust sampling weight
 * return : adjusted sampling weight
 * sampling_ndv (in)  : sampling number of distinct values
 */
STATIC_INLINE int
stats_adjust_sampling_weight (INT64 sampling_ndv, int sampling_weight)
{
  /* This is based on the assumption that if the sample data is a lot of duplicated, */
  /* there will also be duplicate in the overall data. */
  /* Differential weight is applied to NDV within 1% of all rows of sample data. */
  if (sampling_weight <= 1)
    {
      return sampling_weight;
    }
  int min_NDV = NUMBER_OF_SAMPLING_PAGES * EXPECTED_ROWS_PER_PAGE / 100;    /* 1% of number of sampling data */
  if (sampling_ndv < min_NDV)
    {
      return MAX (sampling_weight * sampling_ndv / min_NDV, 1);
    }
  return sampling_weight;
}

#endif /* _STATISTICS_H_ */