Do not understand Filter Expressions on Lookup in TMap

[Anonymous]

I have a very simple job with 4 'contact' records, of which 2 of them have an identical email address





Now I try to find the records have an identical email record. So I load the contact records twice, then both attach them to a tmap, and use a lookup to match on emailaddress. Using filter expressions, I ensure that I don't compare records with themselves.

 

The result now is that only 1 of the duplicate emails is marked as 'duplicate' and the other records is NOT matched. Does anybody have an idea why?

[Anonymous]

Hi Willem,
This is to do with the match model you are using, by default it is unique match. So in this case the output is the result of the last it founds, thus for 3rd record the last match is 4th record -> true [3!=4 => row2.cid is not null] , but for 4th record last match is 4th record -> false [4!=4 => row2.id is null]

If you only want the records that are duplicate use Inner join with All matches as the match model.

But Im also curious about why the 4th record is comared to itself!