pseudorandomfuncs.c File Reference

#include "postgres.h"
#include <math.h>
#include "common/pg_prng.h"
#include "miscadmin.h"
#include "utils/date.h"
#include "utils/fmgrprotos.h"
#include "utils/numeric.h"
#include "utils/timestamp.h"

Include dependency graph for pseudorandomfuncs.c:

Go to the source code of this file.

Macros
#define	CHECK_RANGE_BOUNDS(rmin, rmax)

Functions
static void	initialize_prng (void)
Datum	setseed (PG_FUNCTION_ARGS)
Datum	drandom (PG_FUNCTION_ARGS)
Datum	drandom_normal (PG_FUNCTION_ARGS)
Datum	int4random (PG_FUNCTION_ARGS)
Datum	int8random (PG_FUNCTION_ARGS)
Datum	numeric_random (PG_FUNCTION_ARGS)
Datum	date_random (PG_FUNCTION_ARGS)
Datum	timestamp_random (PG_FUNCTION_ARGS)
Datum	timestamptz_random (PG_FUNCTION_ARGS)

Variables
static pg_prng_state	prng_state
static bool	prng_seed_set = false

Macro Definition Documentation

CHECK_RANGE_BOUNDS

#define CHECK_RANGE_BOUNDS	(		rmin,
			rmax
	)

Value:

    do { \
        if ((rmin) > (rmax)) \
            ereport(ERROR, \
                    errcode(ERRCODE_INVALID_PARAMETER_VALUE), \
                    errmsg("lower bound must be less than or equal to upper bound")); \
    } while (0)

Definition at line 33 of file pseudorandomfuncs.c.

Function Documentation

date_random()

Datum date_random

(

PG_FUNCTION_ARGS

)

Definition at line 203 of file pseudorandomfuncs.c.

{
    int32       rmin = (int32) PG_GETARG_DATEADT(0);
    int32       rmax = (int32) PG_GETARG_DATEADT(1);
    DateADT     result;
 
    CHECK_RANGE_BOUNDS(rmin, rmax);
 
    if (DATE_IS_NOBEGIN(rmin) || DATE_IS_NOEND(rmax))
        ereport(ERROR,
                errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                errmsg("lower and upper bounds must be finite"));
 
    initialize_prng();
 
    result = (DateADT) pg_prng_int64_range(&prng_state, rmin, rmax);
 
    PG_RETURN_DATEADT(result);
}

References CHECK_RANGE_BOUNDS, DATE_IS_NOBEGIN, DATE_IS_NOEND, ereport, errcode(), errmsg(), ERROR, initialize_prng(), PG_GETARG_DATEADT, pg_prng_int64_range(), PG_RETURN_DATEADT, and prng_state.

drandom()

Datum drandom

(

PG_FUNCTION_ARGS

)

Definition at line 97 of file pseudorandomfuncs.c.

{
    float8      result;
 
    initialize_prng();
 
    /* pg_prng_double produces desired result range [0.0, 1.0) */
    result = pg_prng_double(&prng_state);
 
    PG_RETURN_FLOAT8(result);
}

References initialize_prng(), pg_prng_double(), PG_RETURN_FLOAT8, and prng_state.

drandom_normal()

Datum drandom_normal

(

PG_FUNCTION_ARGS

)

Definition at line 115 of file pseudorandomfuncs.c.

{
    float8      mean = PG_GETARG_FLOAT8(0);
    float8      stddev = PG_GETARG_FLOAT8(1);
    float8      result,
                z;
 
    initialize_prng();
 
    /* Get random value from standard normal(mean = 0.0, stddev = 1.0) */
    z = pg_prng_double_normal(&prng_state);
    /* Transform the normal standard variable (z) */
    /* using the target normal distribution parameters */
    result = (stddev * z) + mean;
 
    PG_RETURN_FLOAT8(result);
}

References initialize_prng(), PG_GETARG_FLOAT8, pg_prng_double_normal(), PG_RETURN_FLOAT8, and prng_state.

initialize_prng()

static void initialize_prng ( void  )

static

Definition at line 47 of file pseudorandomfuncs.c.

{
    if (unlikely(!prng_seed_set))
    {
        /*
         * If possible, seed the PRNG using high-quality random bits. Should
         * that fail for some reason, we fall back on a lower-quality seed
         * based on current time and PID.
         */
        if (unlikely(!pg_prng_strong_seed(&prng_state)))
        {
            TimestampTz now = GetCurrentTimestamp();
            uint64      iseed;
 
            /* Mix the PID with the most predictable bits of the timestamp */
            iseed = (uint64) now ^ ((uint64) MyProcPid << 32);
            pg_prng_seed(&prng_state, iseed);
        }
        prng_seed_set = true;
    }
}

References GetCurrentTimestamp(), MyProcPid, now(), pg_prng_seed(), pg_prng_strong_seed, prng_seed_set, prng_state, and unlikely.

Referenced by date_random(), drandom(), drandom_normal(), int4random(), int8random(), numeric_random(), timestamp_random(), and timestamptz_random().

int4random()

Datum int4random

(

PG_FUNCTION_ARGS

)

Definition at line 139 of file pseudorandomfuncs.c.

{
    int32       rmin = PG_GETARG_INT32(0);
    int32       rmax = PG_GETARG_INT32(1);
    int32       result;
 
    CHECK_RANGE_BOUNDS(rmin, rmax);
 
    initialize_prng();
 
    result = (int32) pg_prng_int64_range(&prng_state, rmin, rmax);
 
    PG_RETURN_INT32(result);
}

References CHECK_RANGE_BOUNDS, initialize_prng(), PG_GETARG_INT32, pg_prng_int64_range(), PG_RETURN_INT32, and prng_state.

int8random()

Datum int8random

(

PG_FUNCTION_ARGS

)

Definition at line 160 of file pseudorandomfuncs.c.

{
    int64       rmin = PG_GETARG_INT64(0);
    int64       rmax = PG_GETARG_INT64(1);
    int64       result;
 
    CHECK_RANGE_BOUNDS(rmin, rmax);
 
    initialize_prng();
 
    result = pg_prng_int64_range(&prng_state, rmin, rmax);
 
    PG_RETURN_INT64(result);
}

References CHECK_RANGE_BOUNDS, initialize_prng(), PG_GETARG_INT64, pg_prng_int64_range(), PG_RETURN_INT64, and prng_state.

numeric_random()

Datum numeric_random

(

PG_FUNCTION_ARGS

)

Definition at line 181 of file pseudorandomfuncs.c.

{
    Numeric     rmin = PG_GETARG_NUMERIC(0);
    Numeric     rmax = PG_GETARG_NUMERIC(1);
    Numeric     result;
 
    /* Leave range bound checking to random_numeric() */
 
    initialize_prng();
 
    result = random_numeric(&prng_state, rmin, rmax);
 
    PG_RETURN_NUMERIC(result);
}

References initialize_prng(), PG_GETARG_NUMERIC, PG_RETURN_NUMERIC, prng_state, and random_numeric().

setseed()

Datum setseed

(

PG_FUNCTION_ARGS

)

Definition at line 75 of file pseudorandomfuncs.c.

{
    float8      seed = PG_GETARG_FLOAT8(0);
 
    if (seed < -1 || seed > 1 || isnan(seed))
        ereport(ERROR,
                errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                errmsg("setseed parameter %g is out of allowed range [-1,1]",
                       seed));
 
    pg_prng_fseed(&prng_state, seed);
    prng_seed_set = true;
 
    PG_RETURN_VOID();
}

References ereport, errcode(), errmsg(), ERROR, PG_GETARG_FLOAT8, pg_prng_fseed(), PG_RETURN_VOID, prng_seed_set, and prng_state.

Referenced by assign_random_seed().

timestamp_random()

Datum timestamp_random

(

PG_FUNCTION_ARGS

)

Definition at line 229 of file pseudorandomfuncs.c.

{
    int64       rmin = (int64) PG_GETARG_TIMESTAMP(0);
    int64       rmax = (int64) PG_GETARG_TIMESTAMP(1);
    Timestamp   result;
 
    CHECK_RANGE_BOUNDS(rmin, rmax);
 
    if (TIMESTAMP_IS_NOBEGIN(rmin) || TIMESTAMP_IS_NOEND(rmax))
        ereport(ERROR,
                errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                errmsg("lower and upper bounds must be finite"));
 
    initialize_prng();
 
    result = (Timestamp) pg_prng_int64_range(&prng_state, rmin, rmax);
 
    PG_RETURN_TIMESTAMP(result);
}

References CHECK_RANGE_BOUNDS, ereport, errcode(), errmsg(), ERROR, initialize_prng(), PG_GETARG_TIMESTAMP, pg_prng_int64_range(), PG_RETURN_TIMESTAMP, prng_state, TIMESTAMP_IS_NOBEGIN, and TIMESTAMP_IS_NOEND.

timestamptz_random()

Datum timestamptz_random

(

PG_FUNCTION_ARGS

)

Definition at line 255 of file pseudorandomfuncs.c.

{
    int64       rmin = (int64) PG_GETARG_TIMESTAMPTZ(0);
    int64       rmax = (int64) PG_GETARG_TIMESTAMPTZ(1);
    TimestampTz result;
 
    CHECK_RANGE_BOUNDS(rmin, rmax);
 
    if (TIMESTAMP_IS_NOBEGIN(rmin) || TIMESTAMP_IS_NOEND(rmax))
        ereport(ERROR,
                errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                errmsg("lower and upper bounds must be finite"));
 
    initialize_prng();
 
    result = (TimestampTz) pg_prng_int64_range(&prng_state, rmin, rmax);
 
    PG_RETURN_TIMESTAMPTZ(result);
}

References CHECK_RANGE_BOUNDS, ereport, errcode(), errmsg(), ERROR, initialize_prng(), PG_GETARG_TIMESTAMPTZ, pg_prng_int64_range(), PG_RETURN_TIMESTAMPTZ, prng_state, TIMESTAMP_IS_NOBEGIN, and TIMESTAMP_IS_NOEND.

Variable Documentation

prng_seed_set

bool prng_seed_set = false

static

Definition at line 27 of file pseudorandomfuncs.c.

Referenced by initialize_prng(), and setseed().

prng_state

pg_prng_state prng_state

static

Definition at line 26 of file pseudorandomfuncs.c.

Referenced by choose_dsm_implementation(), date_random(), drandom(), drandom_normal(), initialize_prng(), int4random(), int8random(), numeric_random(), setseed(), timestamp_random(), and timestamptz_random().