pg_statistic.h File Reference

#include "catalog/genbki.h"
#include "catalog/pg_statistic_d.h"

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Macros
#define	STATISTIC_NUM_SLOTS   5

Typedefs
typedef FormData_pg_statistic *	Form_pg_statistic

Functions
	CATALOG (pg_statistic, 2619, StatisticRelationId)
	DECLARE_TOAST (pg_statistic, 2840, 2841)
	DECLARE_UNIQUE_INDEX_PKEY (pg_statistic_relid_att_inh_index, 2696, StatisticRelidAttnumInhIndexId, pg_statistic, btree(starelid oid_ops, staattnum int2_ops, stainherit bool_ops))
	MAKE_SYSCACHE (STATRELATTINH, pg_statistic_relid_att_inh_index, 128)
	DECLARE_FOREIGN_KEY ((starelid, staattnum), pg_attribute,(attrelid, attnum))

Variables
	FormData_pg_statistic

Macro Definition Documentation

STATISTIC_NUM_SLOTS

#define STATISTIC_NUM_SLOTS   5

Definition at line 127 of file pg_statistic.h.

Typedef Documentation

Form_pg_statistic

typedef FormData_pg_statistic* Form_pg_statistic

Definition at line 135 of file pg_statistic.h.

Function Documentation

CATALOG()

CATALOG	(	pg_statistic	,
		2619	,
		StatisticRelationId
	)

Definition at line 29 of file pg_statistic.h.

{
    /* These fields form the unique key for the entry: */
    Oid         starelid BKI_LOOKUP(pg_class);  /* relation containing
                                                 * attribute */
    int16       staattnum;      /* attribute (column) stats are for */
    bool        stainherit;     /* true if inheritance children are included */
 
    /* the fraction of the column's entries that are NULL: */
    float4      stanullfrac;
 
    /*
     * stawidth is the average width in bytes of non-null entries.  For
     * fixed-width datatypes this is of course the same as the typlen, but for
     * var-width types it is more useful.  Note that this is the average width
     * of the data as actually stored, post-TOASTing (eg, for a
     * moved-out-of-line value, only the size of the pointer object is
     * counted).  This is the appropriate definition for the primary use of
     * the statistic, which is to estimate sizes of in-memory hash tables of
     * tuples.
     */
    int32       stawidth;
 
    /* ----------------
     * stadistinct indicates the (approximate) number of distinct non-null
     * data values in the column.  The interpretation is:
     *      0       unknown or not computed
     *      > 0     actual number of distinct values
     *      < 0     negative of multiplier for number of rows
     * The special negative case allows us to cope with columns that are
     * unique (stadistinct = -1) or nearly so (for example, a column in which
     * non-null values appear about twice on the average could be represented
     * by stadistinct = -0.5 if there are no nulls, or -0.4 if 20% of the
     * column is nulls).  Because the number-of-rows statistic in pg_class may
     * be updated more frequently than pg_statistic is, it's important to be
     * able to describe such situations as a multiple of the number of rows,
     * rather than a fixed number of distinct values.  But in other cases a
     * fixed number is correct (eg, a boolean column).
     * ----------------
     */
    float4      stadistinct;
 
    /* ----------------
     * To allow keeping statistics on different kinds of datatypes,
     * we do not hard-wire any particular meaning for the remaining
     * statistical fields.  Instead, we provide several "slots" in which
     * statistical data can be placed.  Each slot includes:
     *      kind            integer code identifying kind of data (see below)
     *      op              OID of associated operator, if needed
     *      coll            OID of relevant collation, or 0 if none
     *      numbers         float4 array (for statistical values)
     *      values          anyarray (for representations of data values)
     * The ID, operator, and collation fields are never NULL; they are zeroes
     * in an unused slot.  The numbers and values fields are NULL in an
     * unused slot, and might also be NULL in a used slot if the slot kind
     * has no need for one or the other.
     * ----------------
     */
 
    int16       stakind1;
    int16       stakind2;
    int16       stakind3;
    int16       stakind4;
    int16       stakind5;
 
    Oid         staop1 BKI_LOOKUP_OPT(pg_operator);
    Oid         staop2 BKI_LOOKUP_OPT(pg_operator);
    Oid         staop3 BKI_LOOKUP_OPT(pg_operator);
    Oid         staop4 BKI_LOOKUP_OPT(pg_operator);
    Oid         staop5 BKI_LOOKUP_OPT(pg_operator);
 
    Oid         stacoll1 BKI_LOOKUP_OPT(pg_collation);
    Oid         stacoll2 BKI_LOOKUP_OPT(pg_collation);
    Oid         stacoll3 BKI_LOOKUP_OPT(pg_collation);
    Oid         stacoll4 BKI_LOOKUP_OPT(pg_collation);
    Oid         stacoll5 BKI_LOOKUP_OPT(pg_collation);
 
#ifdef CATALOG_VARLEN           /* variable-length fields start here */
    float4      stanumbers1[1];
    float4      stanumbers2[1];
    float4      stanumbers3[1];
    float4      stanumbers4[1];
    float4      stanumbers5[1];
 
    /*
     * Values in these arrays are values of the column's data type, or of some
     * related type such as an array element type.  We presently have to cheat
     * quite a bit to allow polymorphic arrays of this kind, but perhaps
     * someday it'll be a less bogus facility.
     */
    anyarray    stavalues1;
    anyarray    stavalues2;
    anyarray    stavalues3;
    anyarray    stavalues4;
    anyarray    stavalues5;
#endif
} FormData_pg_statistic;

References BKI_LOOKUP, and BKI_LOOKUP_OPT.

DECLARE_FOREIGN_KEY()

DECLARE_FOREIGN_KEY	(	(starelid, staattnum)	,
		pg_attribute	,
		(attrelid, attnum)
	)

DECLARE_TOAST()

DECLARE_TOAST	(	pg_statistic	,
		2840	,
		2841
	)

DECLARE_UNIQUE_INDEX_PKEY()

DECLARE_UNIQUE_INDEX_PKEY	(	pg_statistic_relid_att_inh_index	,
		2696	,
		StatisticRelidAttnumInhIndexId	,
		pg_statistic	,
		btree(starelid oid_ops, staattnum int2_ops, stainherit bool_ops)
	)

MAKE_SYSCACHE()

MAKE_SYSCACHE	(	STATRELATTINH	,
		pg_statistic_relid_att_inh_index	,
		128
	)

Variable Documentation

FormData_pg_statistic

FormData_pg_statistic

Definition at line 125 of file pg_statistic.h.