fix(server): save snapshot and delete updates in the same transaction (#12856)

close CLOUD-229



#### PR Dependency Tree


* **PR #12856** 👈

This tree was auto-generated by
[Charcoal](https://github.com/danerwilliams/charcoal)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

- **Refactor**
- Improved the internal handling of document updates and snapshots to
enhance reliability and maintainability. No changes to user-facing
features or functionality.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/backend/server/src/core/doc/storage/doc.ts

@@ -1,4 +1,5 @@
 import { Logger } from '@nestjs/common';
+import { Transactional } from '@nestjs-cls/transactional';
 import {
   applyUpdate,
   diffUpdate,
@@ -78,42 +79,55 @@ export abstract class DocStorageAdapter extends Connection {
     const updates = await this.getDocUpdates(spaceId, docId);
 
     if (updates.length) {
-      this.logger.log(
+      return await this.squashUpdatesToSnapshot(
-        `Squashing updates, spaceId: ${spaceId}, docId: ${docId}, updates: ${updates.length}`
+        spaceId,
-      );
-      const { timestamp, bin, editor } = await this.squash(
-        snapshot ? [snapshot, ...updates] : updates
-      );
-
-      const newSnapshot = {
-        spaceId: spaceId,
         docId,
-        bin,
+        updates,
-        timestamp,
+        snapshot
-        editor,
+      );
-      };
-
-      const success = await this.setDocSnapshot(newSnapshot);
-
-      // if there is old snapshot, create a new history record
-      if (success && snapshot) {
-        await this.createDocHistory(snapshot);
-      }
-
-      // always mark updates as merged unless throws
-      const count = await this.markUpdatesMerged(spaceId, docId, updates);
-      if (count > 0) {
-        this.logger.log(
-          `Marked ${count} updates as merged, spaceId: ${spaceId}, docId: ${docId}`
-        );
-      }
-
-      return newSnapshot;
     }
 
     return snapshot;
   }
 
+  @Transactional()
+  private async squashUpdatesToSnapshot(
+    spaceId: string,
+    docId: string,
+    updates: DocUpdate[],
+    snapshot: DocRecord | null
+  ) {
+    this.logger.log(
+      `Squashing updates, spaceId: ${spaceId}, docId: ${docId}, updates: ${updates.length}`
+    );
+    const { timestamp, bin, editor } = await this.squash(
+      snapshot ? [snapshot, ...updates] : updates
+    );
+
+    const newSnapshot: DocRecord = {
+      spaceId,
+      docId,
+      bin,
+      timestamp,
+      editor,
+    };
+
+    const success = await this.setDocSnapshot(newSnapshot);
+
+    // if there is old snapshot, create a new history record
+    if (success && snapshot) {
+      await this.createDocHistory(snapshot);
+    }
+
+    // always mark updates as merged unless throws
+    const count = await this.markUpdatesMerged(spaceId, docId, updates);
+    this.logger.log(
+      `Marked ${count} updates as merged, spaceId: ${spaceId}, docId: ${docId}, timestamp: ${timestamp}`
+    );
+
+    return newSnapshot;
+  }
+
   async getDocDiff(
     spaceId: string,
     docId: string,