# Pipelines Gotchas

## Critical Issues

### Events Silently Dropped

**Most common issue.** Events accepted (HTTP 200) but never appear in sink.

**Causes:**

1. Schema validation fails - structured streams drop invalid events silently
2. Waiting for roll interval (10-300s) - expected behavior

**Solution:** Validate client-side with Zod:

```typescript
const EventSchema = z.object({ user_id: z.string(), amount: z.number() })
try {
  const validated = EventSchema.parse(rawEvent)
  await env.STREAM.send([validated])
} catch (e) {
  /* get immediate feedback */
}
```

### Pipelines Are Immutable

Cannot modify SQL after creation. Must delete and recreate.

```bash
npx wrangler pipelines delete old-pipeline
npx wrangler pipelines create new-pipeline --sql "..."
```

**Tip:** Use version naming (`events-pipeline-v1`) and keep SQL in version control.

### Worker Binding Not Found

**`env.STREAM is undefined`**

1. Use **stream ID** (not pipeline ID) in `wrangler.jsonc`
2. Redeploy after adding binding

```bash
npx wrangler pipelines streams list  # Get stream ID
npx wrangler deploy
```

## Common Errors

| Error                      | Cause                         | Fix                                 |
| -------------------------- | ----------------------------- | ----------------------------------- |
| Events not in R2           | Roll interval not elapsed     | Wait 10-300s, check `roll_interval` |
| Schema validation failures | Type mismatch, missing fields | Validate client-side                |
| Rate limit (429)           | >5 MB/s per stream            | Batch events, request increase      |
| Payload too large (413)    | >1 MB request                 | Split into smaller batches          |
| Cannot delete stream       | Pipeline references it        | Delete pipelines first              |
| Sink credential errors     | Token expired                 | Recreate sink with new credentials  |

## Limits (Open Beta)

| Resource                            | Limit      |
| ----------------------------------- | ---------- |
| Streams/Sinks/Pipelines per account | 20 each    |
| Payload size                        | 1 MB       |
| Ingest rate per stream              | 5 MB/s     |
| Event retention                     | 24 hours   |
| Recommended batch size              | 100 events |

## SQL Limitations

- **No JOINs** - single stream per pipeline
- **No window functions** - basic SQL only
- **No subqueries** - must use `INSERT INTO ... SELECT ... FROM`
- **No schema evolution** - cannot modify after creation

## Debug Checklist

- [ ] Stream exists: `npx wrangler pipelines streams list`
- [ ] Pipeline healthy: `npx wrangler pipelines get <ID>`
- [ ] SQL syntax matches schema
- [ ] Worker redeployed after binding added
- [ ] Waited for roll interval
- [ ] Accepted vs processed count matches (no validation drops)