wal_decoder: add an is empty method for interpreted record

libs/wal_decoder/src/models.rs

@@ -65,6 +65,18 @@ pub struct InterpretedWalRecord {
     pub xid: TransactionId,
 }
 
+impl InterpretedWalRecord {
+    /// Checks if the WAL record is empty
+    ///
+    /// An empty interpreted WAL record has no data or metadata and does not have to be sent to the
+    /// pageserver.
+    pub fn is_empty(&self) -> bool {
+        self.batch.is_empty()
+            && self.metadata_record.is_none()
+            && matches!(self.flush_uncommitted, FlushUncommittedRecords::No)
+    }
+}
+
 /// The interpreted part of the Postgres WAL record which requires metadata
 /// writes to the underlying storage engine.
 #[derive(Serialize, Deserialize)]

libs/wal_decoder/src/serialized_batch.rs

@@ -496,11 +496,16 @@ impl SerializedValueBatch {
         }
     }
 
-    /// Checks if the batch is empty
-    ///
-    /// A batch is empty when it contains no serialized values.
-    /// Note that it may still contain observed values.
+    /// Checks if the batch contains any serialized or observed values
     pub fn is_empty(&self) -> bool {
+        !self.has_data() && self.metadata.is_empty()
+    }
+
+    /// Checks if the batch contains data
+    ///
+    /// Note that if this returns false, it may still contain observed values or
+    /// a metadata record.
+    pub fn has_data(&self) -> bool {
         let empty = self.raw.is_empty();
 
         if cfg!(debug_assertions) && empty {
@@ -510,7 +515,7 @@ impl SerializedValueBatch {
                 .all(|meta| matches!(meta, ValueMeta::Observed(_))));
         }
 
-        empty
+        !empty
     }
 
     /// Returns the number of values serialized in the batch