UI errors loading traces after Langfuse upgrade: corrupted ClickHouse parts

TL;DR

For "Stream String.size for column projectid/traceid with type String is not found": after upgrading the self-hosted Langfuse docker image, the UI throws internal errors loading traces and traces are unreachable: logs show ClickHouse Stream String.size for column project\id/trace\id with type String is not found and There is no file for column 'id' in data part errors.

Stream String.size for column project_id/trace_id with type String is not found

Steps

1. After upgrading the self-hosted Langfuse docker image, the UI throws internal errors loading traces and traces are unreachable: logs show ClickHouse Stream String.size for column project_id/trace_id with type String is not found and There is no file for column 'id' in data part errors. CHECK TABLE found 17 of 100 parts failing on the observations table.
2. The root cause was storage corruption in ClickHouse data parts (not a migration bug; dirty flags in schemamigrations are normal: golang-migrate always writes a dirty=1 row followed by dirty=0). The maintainer's guidance: run CHECK TABLE traces/observations in ClickHouse to find the failing parts, then `ALTER TABLE [table] DROP PART '[partname]'` for the bad ones. The reporter confirmed Langfuse worked again after cleaning the damaged parts.

When to use

Use this skill when you run into "UI errors loading traces after Langfuse upgrade: corrupted ClickHouse parts".

When not to use

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Versions

No specific versions are mentioned in the source material, so treat the fix as generally applicable and check the examples against whatever you have installed.

Why this happens

The original report does not dig into a root cause. It documents the symptom and the fix that resolved it.

Question: After upgrading the self-hosted Langfuse docker image, the UI throws internal errors loading traces and traces are unreachable: logs show ClickHouse Stream String.size for column project_id/trace_id with type String is not found and There is no file for column 'id' in data part errors. CHECK TABLE found 17 of 100 parts failing on the observations table.

Verified resolution: The root cause was storage corruption in ClickHouse data parts (not a migration bug; dirty flags in schemamigrations are normal: golang-migrate always writes a dirty=1 row followed by dirty=0). The maintainer's guidance: run CHECK TABLE traces/observations in ClickHouse to find the failing parts, then `ALTER TABLE [table] DROP PART '[partname]'` for the bad ones. The reporter confirmed Langfuse worked again after cleaning the damaged parts.

Source: https://github.com/langfuse/langfuse/issues/12172

Thread: https://vectle.com/threads/thr_73tNyxYO0hC1k7sjKpnXWw