posthog

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Problem

We're getting runtime errors in trends queries for dictionary changed size during iteration: https://github.com/PostHog/posthog/issues/23306

We're using the same timings object in multi threaded queries and its getting all jumbled up.

Changes

Modify the timings object to handle cloning in order to pass to a thread while maintaining the current key stack.

Change the trends query to not return redundant timing info and to stack it correctly.

How did you test this code?

Wrote a test for it to make sure it's working as intended. Tested in dev. Can't test multi threaded behavior directly (easily).

🔍 Existing Issues For Review

Your pull request is modifying functions with the following pre-existing issues:

📄 File: posthog/hogql/timings.py

Function	Unhandled Issue
to_dict	RuntimeError: dictionary changed size during iteration posthog.tasks.tasks.process_quer... Event Count: 96
to_dict	TypeError: unsupported operand type(s) for -: 'float' and 'StringDatabaseField' posthog... Event Count: 1

📄 File: posthog/hogql_queries/insights/trends/trends_query_runner.py (Click to Expand)

Function	Unhandled Issue
run	IndexError: list index out of range posthog.tasks... Event Count: 210
calculate	RuntimeError: dictionary changed size during iteration posthog.tasks.tasks.process_quer... Event Count: 96
run	ValidationError: 1 validation error for HogQLQueryResponse posthog.tasks.tasks.process_... Event Count: 34
run	CHQueryErrorCannotParseInputAssertionFailed: DB::Exception: Cannot parse NaN.: while converting 'no-10904' to Float64: while executing 'FUNCTI... ... Event Count: 28
run	CHQueryErrorAuthenticationFailed: DB::Exception: Received from ch12.posthog.net:9000. DB::Exception: default: Authentication failed... ... Event Count: 24

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