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

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value, per recent discussion on pgsql-general.
This commit is contained in:
Tom Lane
2003-04-21 00:22:24 +00:00
parent f9ba0a7fe5
commit 1dc3a62ec7
2 changed files with 18 additions and 34 deletions
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36
src/backend/utils/adt/numeric.c
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@ -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);