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Commit1dc3a62

Browse files
committed
stddev() and variance() should return NULL when there is just one input
value, per recent discussion on pgsql-general.
1 parentf9ba0a7 commit1dc3a62

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2 files changed

+18
-34
lines changed

2 files changed

+18
-34
lines changed

‎src/backend/utils/adt/float.c‎

Lines changed: 5 additions & 11 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $Header: /cvsroot/pgsql/src/backend/utils/adt/float.c,v 1.84 2003/03/11 21:01:33 tgl Exp $
11+
* $Header: /cvsroot/pgsql/src/backend/utils/adt/float.c,v 1.85 2003/04/21 00:22:24 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -1649,12 +1649,9 @@ float8_variance(PG_FUNCTION_ARGS)
16491649
sumX=transvalues[1];
16501650
sumX2=transvalues[2];
16511651

1652-
/* We define VARIANCE of no values to be NULL, of 1 value to be 0 */
1653-
if (N==0.0)
1654-
PG_RETURN_NULL();
1655-
1652+
/* Sample variance is undefined when N is 0 or 1, so return NULL */
16561653
if (N <=1.0)
1657-
PG_RETURN_FLOAT8(0.0);
1654+
PG_RETURN_NULL();
16581655

16591656
numerator=N*sumX2-sumX*sumX;
16601657

@@ -1680,12 +1677,9 @@ float8_stddev(PG_FUNCTION_ARGS)
16801677
sumX=transvalues[1];
16811678
sumX2=transvalues[2];
16821679

1683-
/* We define STDDEV of no values to be NULL, of 1 value to be 0 */
1684-
if (N==0.0)
1685-
PG_RETURN_NULL();
1686-
1680+
/* Sample stddev is undefined when N is 0 or 1, so return NULL */
16871681
if (N <=1.0)
1688-
PG_RETURN_FLOAT8(0.0);
1682+
PG_RETURN_NULL();
16891683

16901684
numerator=N*sumX2-sumX*sumX;
16911685

‎src/backend/utils/adt/numeric.c‎

Lines changed: 13 additions & 23 deletions
Original file line numberDiff line numberDiff line change
@@ -14,7 +14,7 @@
1414
* Copyright (c) 1998-2003, PostgreSQL Global Development Group
1515
*
1616
* IDENTIFICATION
17-
* $Header: /cvsroot/pgsql/src/backend/utils/adt/numeric.c,v 1.59 2003/03/2101:58:04 tgl Exp $
17+
* $Header: /cvsroot/pgsql/src/backend/utils/adt/numeric.c,v 1.60 2003/04/2100:22:24 tgl Exp $
1818
*
1919
*-------------------------------------------------------------------------
2020
*/
@@ -1964,24 +1964,19 @@ numeric_variance(PG_FUNCTION_ARGS)
19641964
if (NUMERIC_IS_NAN(N)||NUMERIC_IS_NAN(sumX)||NUMERIC_IS_NAN(sumX2))
19651965
PG_RETURN_NUMERIC(make_result(&const_nan));
19661966

1967-
/* We define VARIANCE of no values to be NULL, of 1 value to be 0 */
1968-
/* N is zero iff no digits (cf. numeric_uminus) */
1969-
if (N->varlen==NUMERIC_HDRSZ)
1970-
PG_RETURN_NULL();
1971-
1967+
/* Sample variance is undefined when N is 0 or 1, so return NULL */
19721968
init_var(&vN);
19731969
set_var_from_num(N,&vN);
19741970

1975-
init_var(&vNminus1);
1976-
sub_var(&vN,&const_one,&vNminus1);
1977-
1978-
if (cmp_var(&vNminus1,&const_zero) <=0)
1971+
if (cmp_var(&vN,&const_one) <=0)
19791972
{
19801973
free_var(&vN);
1981-
free_var(&vNminus1);
1982-
PG_RETURN_NUMERIC(make_result(&const_zero));
1974+
PG_RETURN_NULL();
19831975
}
19841976

1977+
init_var(&vNminus1);
1978+
sub_var(&vN,&const_one,&vNminus1);
1979+
19851980
init_var(&vsumX);
19861981
set_var_from_num(sumX,&vsumX);
19871982
init_var(&vsumX2);
@@ -2045,24 +2040,19 @@ numeric_stddev(PG_FUNCTION_ARGS)
20452040
if (NUMERIC_IS_NAN(N)||NUMERIC_IS_NAN(sumX)||NUMERIC_IS_NAN(sumX2))
20462041
PG_RETURN_NUMERIC(make_result(&const_nan));
20472042

2048-
/* We define STDDEV of no values to be NULL, of 1 value to be 0 */
2049-
/* N is zero iff no digits (cf. numeric_uminus) */
2050-
if (N->varlen==NUMERIC_HDRSZ)
2051-
PG_RETURN_NULL();
2052-
2043+
/* Sample stddev is undefined when N is 0 or 1, so return NULL */
20532044
init_var(&vN);
20542045
set_var_from_num(N,&vN);
20552046

2056-
init_var(&vNminus1);
2057-
sub_var(&vN,&const_one,&vNminus1);
2058-
2059-
if (cmp_var(&vNminus1,&const_zero) <=0)
2047+
if (cmp_var(&vN,&const_one) <=0)
20602048
{
20612049
free_var(&vN);
2062-
free_var(&vNminus1);
2063-
PG_RETURN_NUMERIC(make_result(&const_zero));
2050+
PG_RETURN_NULL();
20642051
}
20652052

2053+
init_var(&vNminus1);
2054+
sub_var(&vN,&const_one,&vNminus1);
2055+
20662056
init_var(&vsumX);
20672057
set_var_from_num(sumX,&vsumX);
20682058
init_var(&vsumX2);

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