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Add date and timestamp variants of random(min, max).

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This adds 3 new variants of the random() function:

    random(min date, max date) returns date
    random(min timestamp, max timestamp) returns timestamp
    random(min timestamptz, max timestamptz) returns timestamptz

Each returns a random value x in the range min <= x <= max.

Author: Damien Clochard <damien@dalibo.info>
Reviewed-by: Greg Sabino Mullane <htamfids@gmail.com>
Reviewed-by: Dean Rasheed <dean.a.rasheed@gmail.com>
Reviewed-by: Vik Fearing <vik@postgresfriends.org>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Discussion: https://postgr.es/m/f524d8cab5914613d9e624d9ce177d3d@dalibo.info
This commit is contained in:
Dean Rasheed
2025-09-09 10:39:30 +01:00
parent 5ac3c1ac22
commit faf071b553
7 changed files with 254 additions and 10 deletions
Download Patch File Download Diff File Expand all files Collapse all files

104
src/backend/utils/adt/pseudorandomfuncs.c
View File

@@ -17,6 +17,7 @@
#include "common/pg_prng.h"
#include "miscadmin.h"
#include "utils/date.h"
#include "utils/fmgrprotos.h"
#include "utils/numeric.h"
#include "utils/timestamp.h"
@@ -25,6 +26,18 @@
static pg_prng_state prng_state;
static bool prng_seed_set = false;
/*
* Macro for checking the range bounds of random(min, max) functions. Throws
* an error if they're the wrong way round.
*/
#define CHECK_RANGE_BOUNDS(rmin, rmax) \
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)
/*
* initialize_prng() -
*
@@ -129,10 +142,7 @@ int4random(PG_FUNCTION_ARGS)
int32 rmax = PG_GETARG_INT32(1);
int32 result;
if (rmin > rmax)
ereport(ERROR,
errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("lower bound must be less than or equal to upper bound"));
CHECK_RANGE_BOUNDS(rmin, rmax);
initialize_prng();
@@ -153,10 +163,7 @@ int8random(PG_FUNCTION_ARGS)
int64 rmax = PG_GETARG_INT64(1);
int64 result;
if (rmin > rmax)
ereport(ERROR,
errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("lower bound must be less than or equal to upper bound"));
CHECK_RANGE_BOUNDS(rmin, rmax);
initialize_prng();
@@ -177,9 +184,90 @@ numeric_random(PG_FUNCTION_ARGS)
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);
}
/*
* date_random() -
*
* Returns a random date chosen uniformly in the specified range.
*/
Datum
date_random(PG_FUNCTION_ARGS)
{
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);
}
/*
* timestamp_random() -
*
* Returns a random timestamp chosen uniformly in the specified range.
*/
Datum
timestamp_random(PG_FUNCTION_ARGS)
{
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);
}
/*
* timestamptz_random() -
*
* Returns a random timestamptz chosen uniformly in the specified range.
*/
Datum
timestamptz_random(PG_FUNCTION_ARGS)
{
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);
}