[Mondrian] Eigenbase perforce change 14675 for review

Julian Hyde jhyde at pentaho.com
Fri Oct 7 00:23:32 EDT 2011

On Oct 6, 2011, at 6:17 PM, Luc Boudreau wrote:

> The problem appears when doing a count(distinct x) operation. All platforms return the null as a distinct value while Greenplum ignores it. I'll double check everything and revert if necessary. Thanks for the warning.
count(distinct x) should eliminate the duplicates but still not count the null values. Thus, if the table has values {null, 1, 2, 2, 2} it should return 2. If it just has value {null} is should return 0.

(I've implemented the rewrite rule
  select count(distinct x) from t
    --> select count(dx) from (select distinct x as dx from t)
more than once in my RDBMS-implementing career.)

I just checked, and MySQL does this. I'm 99.9% certain Oracle does too.

So... Greenplum is standards-compliant here.

If there's a specific query where Greenplum is giving a dubious result, send me the SQL and I'll check it out.

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