Hi question about user dimensions in GB What happens when a GrowthBook Users #ask-questions

Hi, question about user dimensions in GB: What ha...

prehistoric-beard-84272

09/28/2023, 9:51 AM

Hi, question about user dimensions in GB: What happens when a dimension changes its value for a given identifier? Let's say I use

anonymous_id

(based on device_id) as identifier, and have a dimension

visitor_type

which can have the values "new", "returning", or "customer". The dimension first has the value "new", but on a later visit it will be "returning", because the

anonymous_id

was recognized. So the user becomes part of the experiment with

visitor_type

= "new", and returns and then sees the experiment, but now as

visitor_type

= "returning" How does GB deal with this when I segment the experiment result data by

visitor_type

helpful-application-7107

09/28/2023, 4:06 PM

Great question. This is definitely a blind spot in the app. Because

timestamp

isn't a required field in the User Dimension definition, we have to use some arbitrary rule making to select one user dimension per user (right now we just use

MAX

). On your end, the best way to handle this would be to define your User Dimension using SQL Template variables where you define your user dimension yourself to get the latest record per user that has a

timestamp < {{startDate}}

so that you can ensure all dimensions are pre-experiment (best for bias).

helpful-application-7107

09/28/2023, 4:10 PM

You could do something like the following:

Copy code

WITH visitor_types AS (
SELECT
  anonymous_id,
  visitor_type,
  ROW_NUMBER() OVER (PARTITION BY anonymous_id ORDER BY timestamp DESC) AS rn
FROM
  dim_table
WHERE
  timestamp > DATE_SUB({{startDate}}, INTERVAL 7 DAY) AND timestamp < {{startDate}}
)

SELECT
  anonymous_id,
  visitor_type
FROM visitor_types
WHERE rn = 1

prehistoric-beard-84272

09/29/2023, 6:11 AM

Thank you Luke, I'll try that

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