diff --git a/server/src/engine/storage/v1/tests/batch.rs b/server/src/engine/storage/v1/tests/batch.rs
index 7db00240..6682fe55 100644
--- a/server/src/engine/storage/v1/tests/batch.rs
+++ b/server/src/engine/storage/v1/tests/batch.rs
@@ -79,7 +79,7 @@ fn open_batch_data(fpath: &str, mdl: &Model) -> DataBatchPersistDriver<VirtualFS
 fn new_delta(
     schema: u64,
     txnid: u64,
-    pk: Datacell,
+    pk: impl Into<Datacell>,
     data: DcFieldIndex,
     change: DataDeltaKind,
 ) -> DataDelta {
@@ -105,8 +105,99 @@ fn new_delta_with_row(schema: u64, txnid: u64, row: Row, change: DataDeltaKind)
     )
 }
 
+fn flush_deltas_and_re_read<const N: usize>(
+    mdl: &Model,
+    dt: [DataDelta; N],
+    fname: &str,
+) -> Vec<NormalBatch> {
+    // delta queue
+    let g = pin();
+    for delta in dt {
+        mdl.delta_state().append_new_data_delta(delta, &g);
+    }
+    let file = open_file(fname).into_created().unwrap();
+    {
+        let mut persist_driver = DataBatchPersistDriver::new(file, true).unwrap();
+        persist_driver.write_new_batch(&mdl, N).unwrap();
+        persist_driver.close().unwrap();
+    }
+    let mut restore_driver =
+        DataBatchRestoreDriver::new(open_file(fname).into_existing().unwrap().0).unwrap();
+    let batch = restore_driver.read_all_batches().unwrap();
+    batch
+}
+
 #[test]
-fn deltas_only_insert() {
+fn unskewed_delta() {
+    let uuid = Uuid::new();
+    let mdl = Model::new_restore(
+        uuid,
+        "username".into(),
+        TagSelector::Str.into_full(),
+        into_dict!(
+            "username" => Field::new([Layer::str()].into(), false),
+            "password" => Field::new([Layer::bin()].into(), false)
+        ),
+    );
+    let deltas = [
+        new_delta(
+            0,
+            0,
+            "sayan",
+            into_dict!("password" => Datacell::new_bin("37ae4b773a9fc7a20164eb16".as_bytes().into())),
+            DataDeltaKind::Insert,
+        ),
+        new_delta(
+            0,
+            1,
+            "badguy",
+            into_dict!("password" => Datacell::new_bin("5fe3cbdc470b667cb1ba288a".as_bytes().into())),
+            DataDeltaKind::Insert,
+        ),
+        new_delta(
+            0,
+            2,
+            "doggo",
+            into_dict!("password" => Datacell::new_bin("c80403f9d0ae4d5d0e829dd0".as_bytes().into())),
+            DataDeltaKind::Insert,
+        ),
+        new_delta(0, 3, "badguy", into_dict!(), DataDeltaKind::Delete),
+    ];
+    let batches = flush_deltas_and_re_read(&mdl, deltas, "unskewed_delta.db-btlog");
+    assert_eq!(
+        batches,
+        vec![NormalBatch::new(
+            vec![
+                DecodedBatchEvent::new(
+                    0,
+                    pkey("sayan"),
+                    DecodedBatchEventKind::Insert(vec![Datacell::new_bin(
+                        b"37ae4b773a9fc7a20164eb16".to_vec().into_boxed_slice()
+                    )])
+                ),
+                DecodedBatchEvent::new(
+                    1,
+                    pkey("badguy"),
+                    DecodedBatchEventKind::Insert(vec![Datacell::new_bin(
+                        b"5fe3cbdc470b667cb1ba288a".to_vec().into_boxed_slice()
+                    )])
+                ),
+                DecodedBatchEvent::new(
+                    2,
+                    pkey("doggo"),
+                    DecodedBatchEventKind::Insert(vec![Datacell::new_bin(
+                        b"c80403f9d0ae4d5d0e829dd0".to_vec().into_boxed_slice()
+                    )])
+                ),
+                DecodedBatchEvent::new(3, pkey("badguy"), DecodedBatchEventKind::Delete)
+            ],
+            0
+        )]
+    )
+}
+
+#[test]
+fn skewed_delta() {
     // prepare model definition
     let uuid = Uuid::new();
     let mdl = Model::new_restore(
@@ -139,7 +230,7 @@ fn deltas_only_insert() {
         new_delta(
             0,
             1,
-            Datacell::new_str("good cat".into()),
+            "good cat",
             into_dict!("is_good" => Datacell::new_bool(true), "magical" => Datacell::new_bool(false)),
             DataDeltaKind::Insert,
         ),
@@ -147,34 +238,14 @@ fn deltas_only_insert() {
         new_delta(
             0,
             2,
-            Datacell::new_str("bad cat".into()),
+            "bad cat",
             into_dict!("is_good" => Datacell::new_bool(false), "magical" => Datacell::new_bool(false)),
             DataDeltaKind::Insert,
         ),
         // update catname: Schrödinger's cat, is_good: true, magical: true
         new_delta_with_row(0, 3, row.clone(), DataDeltaKind::Update),
     ];
-    // delta queue
-    let g = pin();
-    for delta in deltas.clone() {
-        mdl.delta_state().append_new_data_delta(delta, &g);
-    }
-    let file = open_file("deltas_only_insert.db-btlog")
-        .into_created()
-        .unwrap();
-    {
-        let mut persist_driver = DataBatchPersistDriver::new(file, true).unwrap();
-        persist_driver.write_new_batch(&mdl, deltas.len()).unwrap();
-        persist_driver.close().unwrap();
-    }
-    let mut restore_driver = DataBatchRestoreDriver::new(
-        open_file("deltas_only_insert.db-btlog")
-            .into_existing()
-            .unwrap()
-            .0,
-    )
-    .unwrap();
-    let batch = restore_driver.read_all_batches().unwrap();
+    let batch = flush_deltas_and_re_read(&mdl, deltas, "skewed_delta.db-btlog");
     assert_eq!(
         batch,
         vec![NormalBatch::new(