retry blob entry migration once on unique violation

app/models/blob_file.rb

@@ -97,16 +97,23 @@ class BlobFile < ReduxApplicationRecord
 
   sig { params(sha256: String).returns(T.nilable(BlobFile)) }
   def self.migrate_sha256!(sha256)
+    retried = T.let(false, T::Boolean)
     # convert to binary if hex formatted
     sha256 = HexUtil.hex2bin(sha256) if sha256.length == 64
-    blob_file = BlobFile.find_by(sha256: sha256)
-    return blob_file if blob_file
-    blob_entry = BlobEntry.find_by(sha256: sha256)
-    return nil unless blob_entry
-    blob_file = BlobFile.find_or_initialize_from_blob_entry(blob_entry)
-    return nil unless blob_file.save
-    logger.info("migrated sha256 #{HexUtil.bin2hex(sha256)} to blob_file")
-    blob_file
+    begin
+      blob_file = BlobFile.find_by(sha256: sha256)
+      return blob_file if blob_file
+      blob_entry = BlobEntry.find_by(sha256: sha256)
+      return nil unless blob_entry
+      blob_file = BlobFile.find_or_initialize_from_blob_entry(blob_entry)
+      return nil unless blob_file.save
+      logger.info("migrated sha256 #{HexUtil.bin2hex(sha256)} to blob_file")
+      blob_file
+    rescue ActiveRecord::RecordNotUnique => e
+      raise e if retried
+      retried = true
+      retry
+    end
   end
 
   sig { params(content_bytes: T.nilable(String)).void }