stddev() and variance() should return NULL when there is just one input

value, per recent discussion on pgsql-general.

diff --git a/src/backend/utils/adt/float.c b/src/backend/utils/adt/float.c
index 4220b47..9520617 100644 (file)
--- a/src/backend/utils/adt/float.c
+++ b/src/backend/utils/adt/float.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *       $Header: /cvsroot/pgsql/src/backend/utils/adt/float.c,v 1.84 2003/03/11 21:01:33 tgl Exp $
+ *       $Header: /cvsroot/pgsql/src/backend/utils/adt/float.c,v 1.85 2003/04/21 00:22:24 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1649,12 +1649,9 @@ float8_variance(PG_FUNCTION_ARGS)
        sumX = transvalues[1];
        sumX2 = transvalues[2];
 
-       /* We define VARIANCE of no values to be NULL, of 1 value to be 0 */
-       if (N == 0.0)
-               PG_RETURN_NULL();
-
+       /* Sample variance is undefined when N is 0 or 1, so return NULL */
        if (N <= 1.0)
-               PG_RETURN_FLOAT8(0.0);
+               PG_RETURN_NULL();
 
        numerator = N * sumX2 - sumX * sumX;
 
@@ -1680,12 +1677,9 @@ float8_stddev(PG_FUNCTION_ARGS)
        sumX = transvalues[1];
        sumX2 = transvalues[2];
 
-       /* We define STDDEV of no values to be NULL, of 1 value to be 0 */
-       if (N == 0.0)
-               PG_RETURN_NULL();
-
+       /* Sample stddev is undefined when N is 0 or 1, so return NULL */
        if (N <= 1.0)
-               PG_RETURN_FLOAT8(0.0);
+               PG_RETURN_NULL();
 
        numerator = N * sumX2 - sumX * sumX;
 

diff --git a/src/backend/utils/adt/numeric.c b/src/backend/utils/adt/numeric.c
index e6698fe..c851ae5 100644 (file)
--- a/src/backend/utils/adt/numeric.c
+++ b/src/backend/utils/adt/numeric.c
@@ -14,7 +14,7 @@
  * Copyright (c) 1998-2003, PostgreSQL Global Development Group
  *
  * IDENTIFICATION
- *       $Header: /cvsroot/pgsql/src/backend/utils/adt/numeric.c,v 1.59 2003/03/21 01:58:04 tgl Exp $
+ *       $Header: /cvsroot/pgsql/src/backend/utils/adt/numeric.c,v 1.60 2003/04/21 00:22:24 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1964,24 +1964,19 @@ numeric_variance(PG_FUNCTION_ARGS)
        if (NUMERIC_IS_NAN(N) || NUMERIC_IS_NAN(sumX) || NUMERIC_IS_NAN(sumX2))
                PG_RETURN_NUMERIC(make_result(&const_nan));
 
-       /* We define VARIANCE of no values to be NULL, of 1 value to be 0 */
-       /* N is zero iff no digits (cf. numeric_uminus) */
-       if (N->varlen == NUMERIC_HDRSZ)
-               PG_RETURN_NULL();
-
+       /* Sample variance is undefined when N is 0 or 1, so return NULL */
        init_var(&vN);
        set_var_from_num(N, &vN);
 
-       init_var(&vNminus1);
-       sub_var(&vN, &const_one, &vNminus1);
-
-       if (cmp_var(&vNminus1, &const_zero) <= 0)
+       if (cmp_var(&vN, &const_one) <= 0)
        {
                free_var(&vN);
-               free_var(&vNminus1);
-               PG_RETURN_NUMERIC(make_result(&const_zero));
+               PG_RETURN_NULL();
        }
 
+       init_var(&vNminus1);
+       sub_var(&vN, &const_one, &vNminus1);
+
        init_var(&vsumX);
        set_var_from_num(sumX, &vsumX);
        init_var(&vsumX2);
@@ -2045,24 +2040,19 @@ numeric_stddev(PG_FUNCTION_ARGS)
        if (NUMERIC_IS_NAN(N) || NUMERIC_IS_NAN(sumX) || NUMERIC_IS_NAN(sumX2))
                PG_RETURN_NUMERIC(make_result(&const_nan));
 
-       /* We define STDDEV of no values to be NULL, of 1 value to be 0 */
-       /* N is zero iff no digits (cf. numeric_uminus) */
-       if (N->varlen == NUMERIC_HDRSZ)
-               PG_RETURN_NULL();
-
+       /* Sample stddev is undefined when N is 0 or 1, so return NULL */
        init_var(&vN);
        set_var_from_num(N, &vN);
 
-       init_var(&vNminus1);
-       sub_var(&vN, &const_one, &vNminus1);
-
-       if (cmp_var(&vNminus1, &const_zero) <= 0)
+       if (cmp_var(&vN, &const_one) <= 0)
        {
                free_var(&vN);
-               free_var(&vNminus1);
-               PG_RETURN_NUMERIC(make_result(&const_zero));
+               PG_RETURN_NULL();
        }
 
+       init_var(&vNminus1);
+       sub_var(&vN, &const_one, &vNminus1);
+
        init_var(&vsumX);
        set_var_from_num(sumX, &vsumX);
        init_var(&vsumX2);