From d535d501d1e1bdb186eb0b5061cd445ef1ac9e7f Mon Sep 17 00:00:00 2001
From: DC <413331538@qq.com>
Date: Tue, 26 Nov 2024 19:48:17 +0800
Subject: [PATCH] [DOCS] Improve description of WAL record format (#14936)

Signed-off-by: DC <413331538@qq.com>
---
 tsdb/docs/format/wal.md | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/tsdb/docs/format/wal.md b/tsdb/docs/format/wal.md
index 39be2a808..db1ce97a8 100644
--- a/tsdb/docs/format/wal.md
+++ b/tsdb/docs/format/wal.md
@@ -17,7 +17,15 @@ Notable deviations are that the record fragment is encoded as:
 └───────────┴──────────┴────────────┴──────────────┘
 ```
 
-The type flag has the following states:
+The initial type byte is made up of three components: a 3-bit reserved field, a 1-bit zstd compression flag, a 1-bit snappy compression flag, and a 3-bit type flag. 
+
+```
+┌─────────────────┬──────────────────┬────────────────────┬──────────────────┐
+│ reserved <3bit> │ zstd_flag <1bit> │ snappy_flag <1bit> │ type_flag <3bit> │
+└─────────────────┴──────────────────┴────────────────────┴──────────────────┘
+```
+
+The lowest 3 bits within this flag represent the record type as follows:
 
 * `0`: rest of page will be empty
 * `1`: a full record encoded in a single fragment