We set up an event that lets people signup on line. The dedupe rule we used on the event is first name, last name, email address (all need to match). A few of the signups created a new contacts, meaning for some reason it didn't find an existing person, but when I looked at these people I find that there is already a contact with the exact same names and email addresses. There are plenty of other people who registered for the event where it found an existing contact to match to.

I thought, well maybe, something isn't exact and went to Find and Merge duplicate contacts. I used the exact same rule. It finds the duplicates.

So why does the rule work sometimes and not other times?

Out of 21 registered 18 already existed. 12 of the 18 matched a record. 6 of the 18 created a duplicate contact.

One guess is there is some trimming going on after the dedupe rule is used. I suppose I can try to test for that.

CiviCRM 4.6.26, Drupal

  • what was your exact rule and weighting and threshold.
    – petednz - fuzion
    Apr 20 '17 at 3:36
  • did the event allow multipe participant regos, and did those who missed tend to be P1, or P>1, since i believe you can have different Rules for each situation can't you (ie one for first, and a different one for additionals)
    – petednz - fuzion
    Apr 20 '17 at 3:38
  • The rule is first name, last name, email. All no length set, weight 1, threshold 3. The event does not allow Register multiple participants.
    – Paul-Tahoe
    Apr 20 '17 at 16:49
  • The only warning I offer for that sort of rule, which seems unlikely to apply in your case (since it would impact in the opposite direction), is that if Contact A has 2 emails that are the same, then if Contact B has a matching Last and Email, they will score 3 (which is a flaw with civi dedupe) and hence will be seen as a match even the first name is different - reminds me i could raise this in jira and get one of my team to look at it
    – petednz - fuzion
    Apr 20 '17 at 20:52

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