backend: add interpreted record replication message type

This is to be used by the safekeeper -> pageserver protocol.

Author: VladLazar

postgres-protocol/src/message/backend.rs

@@ -39,6 +39,7 @@ pub const READY_FOR_QUERY_TAG: u8 = b'Z';
 // replication message tags
 pub const XLOG_DATA_TAG: u8 = b'w';
 pub const PRIMARY_KEEPALIVE_TAG: u8 = b'k';
+pub const INTERPRETED_WAL_RECORD_TAG: u8 = b'0';
 
 // logical replication message tags
 const BEGIN_TAG: u8 = b'B';
@@ -325,6 +326,7 @@ impl Message {
 pub enum ReplicationMessage<D> {
     XLogData(XLogDataBody<D>),
     PrimaryKeepAlive(PrimaryKeepAliveBody),
+    RawInterpretedWalRecords(RawInterpretedWalRecordsBody<D>),
 }
 
 impl ReplicationMessage<Bytes> {
@@ -370,6 +372,15 @@ impl ReplicationMessage<Bytes> {
                     reply,
                 })
             }
+            INTERPRETED_WAL_RECORD_TAG => {
+                let streaming_lsn = buf.read_u64::<BigEndian>()?;
+                let wal_end = buf.read_u64::<BigEndian>()?;
+                ReplicationMessage::RawInterpretedWalRecords(RawInterpretedWalRecordsBody {
+                    streaming_lsn,
+                    wal_end,
+                    data: buf.read_all(),
+                })
+            }
             tag => {
                 return Err(io::Error::new(
                     io::ErrorKind::InvalidInput,
@@ -950,6 +961,30 @@ impl<D> XLogDataBody<D> {
     }
 }
 
+#[derive(Debug)]
+pub struct RawInterpretedWalRecordsBody<D> {
+    streaming_lsn: u64,
+    wal_end: u64,
+    data: D,
+}
+
+impl<D> RawInterpretedWalRecordsBody<D> {
+    #[inline]
+    pub fn streaming_lsn(&self) -> u64 {
+        self.streaming_lsn
+    }
+
+    #[inline]
+    pub fn wal_end(&self) -> u64 {
+        self.wal_end
+    }
+
+    #[inline]
+    pub fn data(&self) -> &D {
+        &self.data
+    }
+}
+
 #[derive(Debug)]
 pub struct PrimaryKeepAliveBody {
     wal_end: u64,