PostHog/posthog

Bug: In Cohorts, the 'set' operator filters in null values for person properties

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#29.916 geöffnet am 13. März 2025

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Beschreibung

Bug description

In Cohorts, 'set' operator filters in null values for person properties.

Expected outcome

  • 'set' should filter out null values
  • 'not set' should include null values

Using Have the property vs Does not have the property doesn't solve this because we want to filter out users who have the property but with a null value.

In filters, 'not set' filters in 'null while 'set' filters it out. This means there's an inconsistency with how we handle this in Cohorts.

How to reproduce

  1. Create a cohort and filter by having a person property that you know some users have null for and select 'set'
  2. notice the list of users includes users with 'null'

You can test with this cohort: https://us.posthog.com/project/53137/cohorts/122367

Additional context

From: https://posthoghelp.zendesk.com/agent/tickets/27021

Debug info

null

Contributor Guide

Tech Stack
python
Domain
backend
Issue Type
bug
SchwierigkeitGeschätzte Implementierungsschwierigkeit für neue Contributors, von 1 für sehr kleine Änderungen bis 5 für Expertenarbeit.
3
Geschätzte ZeitEin grober Zeitrahmen, um zu recherchieren, zu implementieren, zu testen und einen Pull Request vorzubereiten.
1-3 hours
AktivitätsstatusWie verfügbar das Issue gerade wirkt: frisch, aktiv, stale, blockiert oder wartet auf Maintainer-Input.
active
KlarheitWie klar das Issue die erwartete Änderung, Akzeptanzkriterien und den nächsten Schritt erklärt.
clear
Voraussetzungen
Understanding of cohort filteringSQL null handling knowledgeFamiliarity with PostHog property filters
EinsteigerfreundlichkeitEin Score von 1 bis 100, der schätzt, wie zugänglich dieses Issue für First-Time Contributors ist.
50
Research-Richtung
Investigate the cohort filtering logic in the backend, specifically the handling of null values for person properties. Look at the query building code for cohort definitions, likely in the `posthog/models/cohort` or `posthog/queries` directory. Compare the `set` and `not set` operators' behavior with person property filters. Ensure that the SQL query for 'set' excludes null values and 'not set' includes them. Refer to the existing filter logic in `PropertyFilter` classes.