File restore optimization - using snapshot timestamp and file paths (#28546)

* Use snapshot timestamp, remove request for paths at version

* Add timestamp to core Snapshot object

* Avoid mutating function argument

* Explain assumption about editable files

* snapshot.toRaw() in getContentAtVersion

* fix project-history acceptance test

* fix history_v1 test

* fix web tests

* Include the snapshot timestamp in stored chunks

---------

Co-authored-by: Eric Mc Sween <5454374+emcsween@users.noreply.github.com>
GitOrigin-RevId: 376a53e1f927cb56544e6782b47d80345655038c

services/history-v1/api/controllers/projects.js

@@ -28,6 +28,7 @@ const withTmpDir = require('./with_tmp_dir')
 const StreamSizeLimit = require('./stream_size_limit')
 const { getProjectBlobsBatch } = require('../../storage/lib/blob_store')
 const assert = require('../../storage/lib/assert')
+const { getChunkMetadataForVersion } = require('../../storage/lib/chunk_store')
 
 const pipeline = promisify(Stream.pipeline)
 
@@ -396,7 +397,28 @@ async function getSnapshotAtVersion(projectId, version) {
     chunk.getChanges(),
     chunk.getEndVersion() - version
   )
-  snapshot.applyAll(changes)
+
+  if (changes.length > 0) {
+    snapshot.applyAll(changes)
+  } else {
+    // There are no changes in this chunk; we need to look at the previous chunk
+    // to get the snapshot's timestamp
+    let chunkMetadata
+    try {
+      chunkMetadata = await getChunkMetadataForVersion(projectId, version)
+    } catch (err) {
+      if (err instanceof Chunk.VersionNotFoundError) {
+        // The snapshot is the first snapshot of the first chunk, so we can't
+        // find a timestamp. This shouldn't happen often. Ignore the error and
+        // leave the timestamp empty.
+      } else {
+        throw err
+      }
+    }
+
+    snapshot.setTimestamp(chunkMetadata.endTimestamp)
+  }
+
   return snapshot
 }
 

services/history-v1/test/acceptance/js/storage/persist_changes.test.js

@@ -108,6 +108,7 @@ describe('persistChanges', function () {
           content: '',
         },
       },
+      timestamp: thirdChange.getTimestamp().toISOString(),
     })
     const history = new History(snapshot, [thirdChange])
     const currentChunk = new Chunk(history, 2)