fix: stop enabling stable row ids on blob table create (#4126)

This PR stops blob table create from implicitly enabling stable row ids.
A blob schema still selects Lance file format 2.2, but row id behavior
stays with the table config.

Compact then fetch with a `_rowid` captured before compaction is still
not supported on a default table. That needs `take` to remap row
addresses through blob reuse rather than making stable row ids a
blob-table default.

BREAKING CHANGE: blob create no longer enables stable row ids. A blob
schemastill selects Lance file format 2.2. Fetch uses `_rowid` on HEAD.
Held ids survive compact only when the table has stable row ids.


## Testing

* `cargo fmt --all`
* `ruff format .`
* `ruff check .`
* `cargo clippy --quiet --features remote --tests --examples -p lancedb`
* `cargo test --quiet --features remote -p lancedb --test
blob_integration`
* `python/.venv/bin/pytest python/python/tests/test_blob.py -q`

python/python/lancedb/table.py

@@ -1793,6 +1793,9 @@ class Table(ABC):
         The result has the same length and order as ``row_ids``. Null blobs
         produce null slots; valid empty blobs produce ``b""``.
 
+        ``_rowid`` values stay valid after compaction when the table has stable
+        row ids.
+
         Convenience for small payloads. For large values use
         :meth:`fetch_blob_files`.
         """
@@ -1810,6 +1813,9 @@ class Table(ABC):
         The result has the same length and order as ``requests``; null blobs
         produce null slots and empty ranges on non-null blobs produce ``b""``.
 
+        ``_rowid`` values stay valid after compaction when the table has stable
+        row ids.
+
         Row IDs can be obtained from a query with ``with_row_id(True)``. This
         API is currently supported only by local tables.
         """
@@ -1825,6 +1831,9 @@ class Table(ABC):
         ``_rowid`` or a ``_lance_row_id`` field on the blob descriptor. Null
         rows are ``None``. Remote tables require LanceDB Cloud server 0.5.0 or
         newer.
+
+        ``_rowid`` values stay valid after compaction when the table has stable
+        row ids.
         """
 
     @abstractmethod

python/python/tests/test_blob.py

@@ -66,6 +66,25 @@ def _row_ids_by_id(table):
     return dict(zip(hits["id"].to_pylist(), hits["_rowid"].to_pylist()))
 
 
+def _assert_missing_blob_row_ids(exc_info):
+    message = str(exc_info.value)
+    assert "row ids" in message
+    assert "rowaddr" not in message
+    assert "fragment" not in message
+
+
+def _assert_fetch_apis_reject_missing_row_ids(table, row_ids):
+    with pytest.raises(ValueError) as exc_info:
+        table.fetch_blobs("image", row_ids)
+    _assert_missing_blob_row_ids(exc_info)
+    with pytest.raises(ValueError) as exc_info:
+        table.fetch_blob_files("image", row_ids)
+    _assert_missing_blob_row_ids(exc_info)
+    with pytest.raises(ValueError) as exc_info:
+        table.fetch_blob_ranges("image", [(row_id, 0, 1) for row_id in row_ids])
+    _assert_missing_blob_row_ids(exc_info)
+
+
 def test_blob_factory_declares_v2_field():
     field = lancedb.blob("image")
     assert isinstance(field.type, pa.ExtensionType)
@@ -691,6 +710,25 @@ def test_fetch_blobs_accepts_query_result():
     assert {blobs[i].as_py() for i in range(len(blobs))} == {b"gamma"}
 
 
+def test_fetch_blobs_after_compact_with_stable_row_ids(tmp_path):
+    db = lancedb.connect(
+        tmp_path, storage_options={"new_table_enable_stable_row_ids": "true"}
+    )
+    schema = pa.schema([pa.field("id", pa.int64()), lancedb.blob("image")])
+    table = db.create_table("t", schema=schema)
+    table.add([{"id": 1, "image": b"frag-one"}])
+    table.add([{"id": 2, "image": b"frag-two"}])
+    by_id = _row_ids_by_id(table)
+    ids = [by_id[1], by_id[2]]
+
+    table.optimize()
+
+    blobs = table.fetch_blobs("image", ids)
+    assert blobs.to_pylist() == [b"frag-one", b"frag-two"]
+    ranges = table.fetch_blob_ranges("image", [(ids[0], 5, 3), (ids[1], 5, 3)])
+    assert ranges.to_pylist() == [b"one", b"two"]
+
+
 def test_fetch_blobs_preserves_null_and_empty_values():
     table = _blob_table(
         "nulls",
@@ -739,8 +777,25 @@ def test_fetch_blob_ranges_validates_requests():
     with pytest.raises(ValueError, match="offset \\+ length overflowed"):
         table.fetch_blob_ranges("image", [(row_id, 2**64 - 1, 1)])
 
-    with pytest.raises(ValueError, match="row IDs"):
+    with pytest.raises(ValueError) as exc_info:
         table.fetch_blob_ranges("image", [(2**64 - 1, 0, 1)])
+    _assert_missing_blob_row_ids(exc_info)
+
+
+def test_fetch_blob_apis_reject_missing_fragment_row_addr():
+    table = _blob_table("missing_frag", [{"id": 1, "image": b"x"}])
+    live = _row_ids_by_id(table)[1]
+    _assert_fetch_apis_reject_missing_row_ids(table, [1 << 32, live])
+
+
+def test_fetch_blob_apis_reject_deleted_row_ids():
+    table = _blob_table(
+        "deleted_rows",
+        [{"id": 1, "image": b"one"}, {"id": 2, "image": b"two"}],
+    )
+    by_id = _row_ids_by_id(table)
+    table.delete("id = 2")
+    _assert_fetch_apis_reject_missing_row_ids(table, [by_id[2], by_id[1]])
 
 
 def test_fetch_blob_ranges_empty_requests_returns_empty_array():