From cd575976f6f8a43e209991633b9cfe3656fbba7e Mon Sep 17 00:00:00 2001 From: Neil Conway Date: Wed, 19 Sep 2007 22:31:51 +0000 Subject: [PATCH] Prevent corr() from returning the wrong results for negative correlation values. The previous coding essentially assumed that x = sqrt(x*x), which does not hold for x < 0. Thanks to Jie Zhang at Greenplum and Gavin Sherry for reporting this issue. --- src/backend/utils/adt/float.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/src/backend/utils/adt/float.c b/src/backend/utils/adt/float.c index 9b734c0ec6..0782fdceb4 100644 --- a/src/backend/utils/adt/float.c +++ b/src/backend/utils/adt/float.c @@ -2274,8 +2274,7 @@ float8_corr(PG_FUNCTION_ARGS) if (numeratorX <= 0 || numeratorY <= 0) PG_RETURN_NULL(); - PG_RETURN_FLOAT8(sqrt((numeratorXY * numeratorXY) / - (numeratorX * numeratorY))); + PG_RETURN_FLOAT8(numeratorXY / sqrt(numeratorX * numeratorY)); } Datum -- 2.39.5