From f4e3042eaae5606b280d2d09a44ac54570518567 Mon Sep 17 00:00:00 2001
From: ggershinsky <ggershinsky@users.noreply.github.com>
Date: Wed, 25 Sep 2024 08:52:30 +0300
Subject: [PATCH] GH-452: Clarify use of RowGroup.ordinal field (#453)

* clarify rg ordinal in readers

* nit: sentence structure
---
 Encryption.md | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/Encryption.md b/Encryption.md
index 008519b2..180b9aa6 100644
--- a/Encryption.md
+++ b/Encryption.md
@@ -356,6 +356,11 @@ struct RowGroup {
 }
 ```
 
+The integrity of this field is protected by authenticated encryption of the footer (FileMetaData). Therefore, 
+the reader implementations can use either a local row group counter (ordinal) or the `RowGroup.ordinal`
+field as an input to AAD suffix calculation. The latter option can be helpful when different reader 
+threads process different row groups in the same parquet file.
+
 A `crypto_metadata` field is set in each ColumnChunk in the encrypted columns. ColumnCryptoMetaData 
 is a union - the actual structure is chosen depending on whether the column is encrypted with the 
 footer encryption key, or with a column-specific key. For the latter, a key metadata can be specified.