mirror of
https://git.postgresql.org/git/postgresql.git
synced 2024-08-18 10:13:23 +02:00
308 lines
5.3 KiB
C
308 lines
5.3 KiB
C
|
/* ----------
|
||
|
* Module statmath
|
||
|
*
|
||
|
* statistical aggregates for average, variance and standard
|
||
|
* deviation.
|
||
|
*
|
||
|
* Jan Wieck
|
||
|
* ----------
|
||
|
*/
|
||
|
|
||
|
#include <stdio.h>
|
||
|
#include <stdlib.h>
|
||
|
#include <math.h>
|
||
|
#include <errno.h>
|
||
|
|
||
|
#include "postgres.h"
|
||
|
#include "utils/palloc.h"
|
||
|
|
||
|
|
||
|
/* ----------
|
||
|
* Declarations
|
||
|
*
|
||
|
* statmath_stateval_in() Input function for state transition variable
|
||
|
* statmath_stateval_out() Output function for state transition variable
|
||
|
* statmath_collect() State transition function to collect items
|
||
|
* statmath_average_fin() Final function for average aggregate
|
||
|
* statmath_variance_fin() Final function for variance aggregate
|
||
|
* statmath_stddev_fin() Final function for deviation aggregate
|
||
|
* ----------
|
||
|
*/
|
||
|
|
||
|
float64 statmath_stateval_in(char *str);
|
||
|
char *statmath_stateval_out(float64 sval);
|
||
|
|
||
|
float64 statmath_collect(float64 sval, float64 item);
|
||
|
float64 statmath_average_fin(float64 sval, int4 n);
|
||
|
float64 statmath_variance_fin(float64 sval, int4 n);
|
||
|
float64 statmath_stddev_fin(float64 sval, int4 n);
|
||
|
|
||
|
|
||
|
/* ----------
|
||
|
* statmath_checkval -
|
||
|
*
|
||
|
* Bounds checking for float8 values in Postgres
|
||
|
* ----------
|
||
|
*/
|
||
|
static void
|
||
|
statmath_checkval(double val)
|
||
|
{
|
||
|
if (fabs(val) > DBL_MAX)
|
||
|
elog(ERROR, "statmath: overflow");
|
||
|
if (val != 0.0 && fabs(val) < DBL_MIN)
|
||
|
elog(ERROR, "statmath: underflow");
|
||
|
}
|
||
|
|
||
|
|
||
|
/* ----------
|
||
|
* statmath_stateval_in -
|
||
|
*
|
||
|
* Input function for the state transition value data type.
|
||
|
* The input string are two float8's separated with a colon ':'.
|
||
|
* ----------
|
||
|
*/
|
||
|
float64
|
||
|
statmath_stateval_in(char *str)
|
||
|
{
|
||
|
float64 retval;
|
||
|
double tmp;
|
||
|
char *cp1, *cp2;
|
||
|
|
||
|
if (!str)
|
||
|
return (float64) NULL;
|
||
|
|
||
|
/*
|
||
|
* Allocate space for the result
|
||
|
*/
|
||
|
retval = (float64) palloc(sizeof(float64data) * 2);
|
||
|
|
||
|
/*
|
||
|
* Get the first number
|
||
|
*/
|
||
|
errno = 0;
|
||
|
tmp = strtod(str, &cp1);
|
||
|
if (*cp1 != ':' || errno == ERANGE)
|
||
|
elog(ERROR, "statmath: illegal input format '%s'", str);
|
||
|
statmath_checkval(tmp);
|
||
|
retval[0] = tmp;
|
||
|
|
||
|
/*
|
||
|
* Get the second number
|
||
|
*/
|
||
|
tmp = strtod(++cp1, &cp2);
|
||
|
if (*cp2 != '\0' || errno == ERANGE)
|
||
|
elog(ERROR, "statmath: illegal input format '%s'", str);
|
||
|
statmath_checkval(tmp);
|
||
|
retval[1] = tmp;
|
||
|
|
||
|
/*
|
||
|
* Return the internal binary format
|
||
|
*/
|
||
|
return retval;
|
||
|
}
|
||
|
|
||
|
|
||
|
/* ----------
|
||
|
* statmath_stateval_out -
|
||
|
*
|
||
|
* Output function for the state transition value data type.
|
||
|
* ----------
|
||
|
*/
|
||
|
char *
|
||
|
statmath_stateval_out(float64 sval)
|
||
|
{
|
||
|
char buf[1024];
|
||
|
double v1, v2;
|
||
|
|
||
|
if (!sval)
|
||
|
return pstrdup("(null)");
|
||
|
|
||
|
/*
|
||
|
* Print the values in the external format and return
|
||
|
* the result in allocated space
|
||
|
*/
|
||
|
v1 = sval[0];
|
||
|
v2 = sval[1];
|
||
|
sprintf(buf, "%.*g:%.*g", DBL_DIG, v1, DBL_DIG, v2);
|
||
|
return pstrdup(buf);
|
||
|
}
|
||
|
|
||
|
|
||
|
/* ----------
|
||
|
* statmath_collect -
|
||
|
*
|
||
|
* State transition function to collect data for the variance
|
||
|
* and standard deviation aggregates.
|
||
|
* The state transition variable holds 2 float8 values. The
|
||
|
* first is the sum of the items, the second the sum of the
|
||
|
* item quadratic products.
|
||
|
* ----------
|
||
|
*/
|
||
|
float64
|
||
|
statmath_collect(float64 sval, float64 item)
|
||
|
{
|
||
|
float64 retval;
|
||
|
double tmp;
|
||
|
|
||
|
if (!sval || !item)
|
||
|
return (float64) NULL;
|
||
|
|
||
|
/*
|
||
|
* Allocate space for the result
|
||
|
*/
|
||
|
retval = (float64) palloc(sizeof(float64data) * 2);
|
||
|
|
||
|
/*
|
||
|
* Compute the new values
|
||
|
*/
|
||
|
tmp = sval[0] + *item;
|
||
|
statmath_checkval(tmp);
|
||
|
retval[0] = tmp;
|
||
|
|
||
|
tmp = sval[1] + *item * *item;
|
||
|
statmath_checkval(tmp);
|
||
|
retval[1] = tmp;
|
||
|
|
||
|
/*
|
||
|
* Return the result
|
||
|
*/
|
||
|
return retval;
|
||
|
}
|
||
|
|
||
|
|
||
|
/* ----------
|
||
|
* statmath_average_fin -
|
||
|
*
|
||
|
* Final computation function for the average aggregate.
|
||
|
* ----------
|
||
|
*/
|
||
|
float64
|
||
|
statmath_average_fin(float64 sum, int4 n)
|
||
|
{
|
||
|
float64 retval;
|
||
|
double tmp;
|
||
|
|
||
|
if (!sum)
|
||
|
return (float64) NULL;
|
||
|
|
||
|
/*
|
||
|
* Allocate space for the result
|
||
|
*/
|
||
|
retval = (float64) palloc(sizeof(float64data));
|
||
|
|
||
|
/*
|
||
|
* Avoid division by zero if no items collected
|
||
|
*/
|
||
|
if (n == 0)
|
||
|
{
|
||
|
*retval = 0.0;
|
||
|
return retval;
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* Compute the average
|
||
|
*/
|
||
|
tmp = *sum / (double)n;
|
||
|
statmath_checkval(tmp);
|
||
|
*retval = tmp;
|
||
|
|
||
|
/*
|
||
|
* Return the result
|
||
|
*/
|
||
|
return retval;
|
||
|
}
|
||
|
|
||
|
|
||
|
/* ----------
|
||
|
* statmath_variance_fin -
|
||
|
*
|
||
|
* Final computation function for the variance aggregate
|
||
|
* ----------
|
||
|
*/
|
||
|
float64
|
||
|
statmath_variance_fin(float64 sval, int4 n)
|
||
|
{
|
||
|
float64 retval;
|
||
|
double avg;
|
||
|
double variance;
|
||
|
|
||
|
if (!sval)
|
||
|
return (float64) NULL;
|
||
|
|
||
|
/*
|
||
|
* Allocate space for the result
|
||
|
*/
|
||
|
retval = (float64) palloc(sizeof(float64data));
|
||
|
|
||
|
/*
|
||
|
* Avoid division by zero if less than 2 items collected
|
||
|
*/
|
||
|
if (n < 2)
|
||
|
{
|
||
|
*retval = 0.0;
|
||
|
return retval;
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* Calculate the variance
|
||
|
*/
|
||
|
avg = sval[0] / (double)n;
|
||
|
variance = (sval[1] - sval[0] * avg) / ((double)n - 1.0);
|
||
|
|
||
|
statmath_checkval(variance);
|
||
|
*retval = variance;
|
||
|
|
||
|
/*
|
||
|
* Return the result
|
||
|
*/
|
||
|
return retval;
|
||
|
}
|
||
|
|
||
|
|
||
|
/* ----------
|
||
|
* statmath_stateval_in -
|
||
|
*
|
||
|
* Input function for the state transition value data type
|
||
|
* ----------
|
||
|
*/
|
||
|
float64
|
||
|
statmath_stddev_fin(float64 sval, int4 n)
|
||
|
{
|
||
|
float64 retval;
|
||
|
double avg;
|
||
|
double stddev;
|
||
|
|
||
|
if (!sval)
|
||
|
return (float64) NULL;
|
||
|
|
||
|
/*
|
||
|
* Allocate space for the result
|
||
|
*/
|
||
|
retval = (float64) palloc(sizeof(float64data));
|
||
|
|
||
|
/*
|
||
|
* Avoid division by zero if less than 2 items collected
|
||
|
*/
|
||
|
if (n < 2)
|
||
|
{
|
||
|
*retval = 0.0;
|
||
|
return retval;
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* Calculate the standard deviation
|
||
|
*/
|
||
|
avg = sval[0] / (double)n;
|
||
|
stddev = sqrt((sval[1] - sval[0] * avg) / ((double)n - 1.0));
|
||
|
|
||
|
statmath_checkval(stddev);
|
||
|
*retval = stddev;
|
||
|
|
||
|
/*
|
||
|
* Return the result
|
||
|
*/
|
||
|
return retval;
|
||
|
}
|
||
|
|
||
|
|