Thread: pgsql: Prevent corr() from returning the wrong results for negative

Log Message:
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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.

Tags:
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REL8_2_STABLE

Modified Files:
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    pgsql/src/backend/utils/adt:
        float.c (r1.130 -> r1.130.2.1)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/float.c?r1=1.130&r2=1.130.2.1)