[mob] Log when clip embeddings are read from DB

mobile/lib/db/ml/clip_db.dart

@@ -1,6 +1,7 @@
 import "dart:io";
 import "dart:typed_data";
 
+import "package:logging/logging.dart";
 import "package:photos/core/event_bus.dart";
 import "package:photos/db/ml/db.dart";
 import "package:photos/db/ml/db_fields.dart";
@@ -19,6 +20,7 @@ extension ClipDB on MLDataDB {
   }
 
   Future<List<EmbeddingVector>> getAllClipVectors() async {
+    Logger("ClipDB").info("reading all embeddings from DB");
     final db = await MLDataDB.instance.asyncDB;
     final results = await db.getAll('SELECT * FROM $clipTable');
     return _convertToVectors(results);

mobile/lib/db/ml/db.dart

@@ -30,6 +30,8 @@ class MLDataDB {
 
   static const _databaseName = "ente.ml.db";
 
+  static Logger get logger => _logger;
+
   // static const _databaseVersion = 1;
 
   MLDataDB._privateConstructor();

mobile/lib/services/machine_learning/semantic_search/semantic_search_service.dart

@@ -108,8 +108,12 @@ class SemanticSearchService {
   }
 
   Future<List<EmbeddingVector>> getClipVectors() async {
-    _logger.info("Pulling cached clip embeddings");
+    if (_cachedImageEmbeddingVectors != null) {
+      return _cachedImageEmbeddingVectors!;
+    }
     _cachedImageEmbeddingVectors ??= MLDataDB.instance.getAllClipVectors();
+    _logger.info("read all embeddings from DB");
+
     return _cachedImageEmbeddingVectors!;
   }