## TL;DR
Shrink the metric query before blaming the warehouse: the Metaplane metric computation timed out because the monitor scans too much history or an unpartitioned table, so scope the metric to its window, use the warehouse partition filter, and pre-aggregate where the monitor allows. Monitor queries run on a schedule against growing tables. A metric that was fast at launch becomes a full scan as the table grows, until it crosses the warehouse query timeout.

```text
Metaplane monitor failed error "metric computation timed out on warehouse query"
```

## Use this when
- The check or run fails with this symptom: a Metaplane monitor fails with metric computation timed out on a warehouse query.
- You are working on a Metaplane monitor computing a metric over a large or growing warehouse table and the failure repeats on the same data or configuration.
- You need the failing rows, rule, or stage isolated before changing thresholds or code.

## Not for this skill when
- A warehouse outage or a runaway shared workload, where every monitor times out at once and the platform is the cause.
- The error text names a different tool, stage, or root cause. Match the verbatim error first and use that skill.

## Steps
1. Open the monitor and read the metric definition and its lookback window. Verify: the window and the scanned table are known
2. Run the equivalent query manually with a timer. Verify: the query duration and scanned volume confirm the monitor query is the slow part
3. Add or fix the partition filter so the query reads only its window. Verify: scanned volume drops to the window size
4. Where the metric allows, point it at a pre-aggregated table maintained by the pipeline. Verify: the monitor query completes in seconds
5. Rerun the monitor. Verify: it completes inside the timeout and reports a value

## Variant phrasings
### metaplane metric computation timed out warehouse query
The shorter phrasing focused on the named failure.
### metaplane monitor failed metric timeout
The symptom phrasing a searcher tries next.
### metaplane monitor slow query fix
The variant naming the failing stage or tool directly.

Compatibility: Metaplane monitors and warehouse query timeouts

## Why it happens
Metric monitors express what to compute, and the generated query inherits the table full size unless the metric is scoped to a window and the table is partitioned by the filtered column. Growth turns a reasonable query into a timeout without any change in the monitor itself.

## Edge cases / pitfalls
- Raising the warehouse timeout for monitors delays every other alert behind the same slow query; fix the scan first.
- Check whether other monitors share the table; one unpartitioned table usually explains a cluster of timing out monitors.

## Provenance

Resolved from the public thread: https://vectle.com/posts/pst_gOn-t27zx3Gh8nHDqreXSQ