## ✅ Checklist
- [ ] I have followed every step in the [contributing
guide](https://github.com/triggerdotdev/trigger.dev/blob/main/CONTRIBUTING.md)
- [x] The PR title follows the convention.
- [ ] I ran and tested the code works
---
## Testing
`pnpm run typecheck --filter @internal/clickhouse` passes. This only
adds a ClickHouse input-format setting to existing insert calls; the
setting affects type inference for newly-inserted/merged data and is
non-destructive to existing rows.
---
## Changelog
Sets
`input_format_json_infer_array_of_dynamic_from_array_of_different_types
= 1` on every native-JSON insert path:
- `task_runs_v2` (`output`, `error`) — `insertTaskRuns`,
`insertTaskRunsCompactArrays`, and the async-insert variants
- `task_events_v1` / `task_events_v2` (`attributes`)
- `metrics_v1`
- `sessions_v1`
### Why
Our JSON columns contain arrays with mixed element types (e.g.
`[{"key":"value"}, "string", "string"]`). With this setting off — which
is the effective default under `24.12` compatibility — ClickHouse infers
those as deeply nested unnamed `Tuple(JSON, Nullable(String), …)` types.
ClickHouse 26.2 introduced `input_format_binary_max_type_complexity`
(default 1000), and those tuple type trees exceeded the limit, causing
background merges to fail with **Code 117**.
With the setting on (the default since 25.8), mixed-type arrays are
inferred as a single `Array(Dynamic)` — a simpler, flatter type
representation that never approaches the complexity limit, even once the
upstream default limit is restored.
Setting this explicitly at insert time keeps behavior deterministic and
version-controlled, so it does not depend on the server profile or a
future compatibility bump. This is a forward-only change: it only
affects newly inserted/merged data and does not rewrite existing parts.
Our read path re-serializes these columns to strings (`toJSONString` via
the materialized `*_text` columns), so the internal Tuple →
Array(Dynamic) representation change is transparent to the application.
### Companion server-side setting
To also apply this on the ClickHouse side (covers merges and any writes
not going through these code paths), set it on the default user:
```sql
ALTER USER default SETTINGS input_format_json_infer_array_of_dynamic_from_array_of_different_types = 1;
```
---
## Screenshots
_N/A_
💯🤖 Generated with [Claude Code](https://claude.com/claude-code)
https://claude.ai/code/session_01AaChyhestFMBYBWh6bgcCF
---
_Generated by [Claude
Code](https://claude.ai/code/session_01AaChyhestFMBYBWh6bgcCF)_
---------
Co-authored-by: Claude <noreply@anthropic.com>
Matt Aitken
536731a5d6