# VEX Raw Migration Rollback Guide

This document describes how to rollback migrations applied to the `vex_raw` collection.

## Migration: 20251127-vex-raw-idempotency-indexes

### Description
Adds unique idempotency indexes to enforce content-addressed storage:
- `idx_provider_sourceUri_digest_unique`: Prevents duplicate documents from same provider/source
- `idx_digest_providerId`: Optimizes evidence queries by digest
- `idx_retrievedAt`: Supports time-based queries and future TTL operations

### Rollback Steps

#### Option 1: MongoDB Shell

```javascript
// Connect to your MongoDB instance
mongosh "mongodb://localhost:27017/excititor"

// Drop the idempotency indexes
db.vex_raw.dropIndex("idx_provider_sourceUri_digest_unique")
db.vex_raw.dropIndex("idx_digest_providerId")
db.vex_raw.dropIndex("idx_retrievedAt")

// Verify indexes are dropped
db.vex_raw.getIndexes()
```

#### Option 2: Programmatic Rollback (C#)

```csharp
using StellaOps.Excititor.Storage.Mongo.Migrations;

// Get the database instance
var database = client.GetDatabase("excititor");

// Execute rollback
await database.RollbackIdempotencyIndexesAsync(cancellationToken);

// Verify rollback
var verified = await database.VerifyIdempotencyIndexesExistAsync(cancellationToken);
Console.WriteLine($"Indexes exist after rollback: {verified}"); // Should be false
```

#### Option 3: MongoDB Compass

1. Connect to your MongoDB instance
2. Navigate to the `excititor` database
3. Select the `vex_raw` collection
4. Go to the "Indexes" tab
5. Click "Drop Index" for each of:
   - `idx_provider_sourceUri_digest_unique`
   - `idx_digest_providerId`
   - `idx_retrievedAt`

### Impact of Rollback

**Before rollback (indexes present):**
- Documents are prevented from being duplicated
- Evidence queries are optimized
- Unique constraint enforced

**After rollback (indexes dropped):**
- Duplicate documents may be inserted
- Evidence queries may be slower
- No unique constraint enforcement

### Re-applying the Migration

To re-apply the migration after rollback:

```javascript
// MongoDB shell
db.vex_raw.createIndex(
  { "providerId": 1, "sourceUri": 1, "digest": 1 },
  { unique: true, name: "idx_provider_sourceUri_digest_unique", background: true }
)

db.vex_raw.createIndex(
  { "digest": 1, "providerId": 1 },
  { name: "idx_digest_providerId", background: true }
)

db.vex_raw.createIndex(
  { "retrievedAt": 1 },
  { name: "idx_retrievedAt", background: true }
)
```

Or run the migration runner:

```bash
stellaops excititor migrate --run 20251127-vex-raw-idempotency-indexes
```

## Migration: 20251125-vex-raw-json-schema

### Description
Adds a JSON Schema validator to the `vex_raw` collection with `validationAction: warn`.

### Rollback Steps

```javascript
// MongoDB shell - remove the validator
db.runCommand({
  collMod: "vex_raw",
  validator: {},
  validationAction: "off",
  validationLevel: "off"
})

// Verify validator is removed
db.getCollectionInfos({ name: "vex_raw" })[0].options
```

### Impact of Rollback

- Documents will no longer be validated against the schema
- Invalid documents may be inserted
- Existing documents are not affected

## General Rollback Guidelines

1. **Always backup first**: Create a backup before any rollback operation
2. **Test in staging**: Verify rollback procedure in a non-production environment
3. **Monitor performance**: Watch for query performance changes after rollback
4. **Document changes**: Log all rollback operations for audit purposes

## Troubleshooting

### Index Drop Fails

If you see "IndexNotFound" errors, the index may have already been dropped or was never created:

```javascript
// Check existing indexes
db.vex_raw.getIndexes()
```

### Validator Removal Fails

If the validator command fails, verify you have the correct permissions:

```javascript
// Check current user roles
db.runCommand({ usersInfo: 1 })
```

## Related Documentation

- [VEX Raw Schema Validation](vex-raw-schema-validation.md)
- [MongoDB Index Management](https://www.mongodb.com/docs/manual/indexes/)
- [Excititor Architecture](../modules/excititor/architecture.md)