perf: Use UDF everywhere

[timgl]

Problem

clicking on a funnel step to get persons is slow, mostly because we take a long time to parse hogql

Changes

Use UDF instead

👉 Stay up-to-date with PostHog coding conventions for a smoother review.

Does this work well for both Cloud and self-hosted?

How did you test this code?

[greptile-apps]

PR Summary

This PR improves performance by consistently using User Defined Functions (UDFs) across all funnel queries, reducing HogQL parsing time when retrieving persons from funnel steps.

• Removed the conditional use_udf() function from posthog/hogql_queries/insights/funnels/utils.py and its related imports
• Modified posthog/hogql_queries/insights/funnels/funnel_correlation_query_runner.py to hardcode True for UDF usage in get_funnel_actor_class()
• Removed the _use_udf cached property from posthog/hogql_queries/insights/funnels/funnels_query_runner.py and set use_udf=True in funnel class instantiations
• Set isUdf=True in the response object to ensure consistent UDF usage throughout the funnel query process

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[aspicer]

👍

[timgl]

@aspicer was there a reason you didn't do this before?

[aspicer]

Does this do anything other than removing the feature flags? The feature flags are fully enabled, so I'm not sure this functionally changes anything.

How is this supposed to address the hogql parsing performance? Maybe I'm missing something there?

[timgl]

@aspicer It was specifically for clicking on a step in a funnel. With this change we now use UDF, which means we don't have to spend ~5 seconds parsing Hogql

[aspicer]

@aspicer It was specifically for clicking on a step in a funnel. With this change we now use UDF, which means we don't have to spend ~5 seconds parsing Hogql

Do you mean clicking on the funnel and bringing up the actors modal like below? If so, that already uses UDFs.

Or something else that I'm missing?

UDFs don't support unordered funnels yet, and I'm converting time to convert funnels now.

[timgl]

@aspicer Ah, this is the context, and they use unordered funnels which I suppose is why it wasn't using UDF. Is unordered support on your roadmap for this?

EDIT: looks like Thomas came to the same conclusion a few hours ago: #28878 (comment). Let me know if you still want to merge this just for clean up or not.

[aspicer]

@timgl Yes, it's on the roadmap for this quarter. The goal is to create the ability for more funnel flexibility, so that people could, for example, do

Step 1
Step 2,3,4 (any order, perhaps optional)
Step 5

and track that throughout the funnel.

There's a chance that fully unordered funnels would come first, but I'll have to see if it makes sense when I get into the code.