feat(python): add count_rows with filter option (#801)

Closes #795

python/lancedb/table.py

@@ -647,8 +647,19 @@ class LanceTable(Table):
         self._dataset.restore()
         self._reset_dataset()
 
+    def count_rows(self, filter: Optional[str] = None) -> int:
+        """
+        Count the number of rows in the table.
+
+        Parameters
+        ----------
+        filter: str, optional
+            A SQL where clause to filter the rows to count.
+        """
+        return self._dataset.count_rows(filter)
+
     def __len__(self):
-        return self._dataset.count_rows()
+        return self.count_rows()
 
     def __repr__(self) -> str:
         return f"LanceTable({self.name})"

python/tests/test_table.py

@@ -597,3 +597,14 @@ def test_compact_cleanup(db):
 
     with pytest.raises(Exception, match="Version 3 no longer exists"):
         table.checkout(3)
+
+
+def test_count_rows(db):
+    table = LanceTable.create(
+        db,
+        "my_table",
+        data=[{"text": "foo", "id": 0}, {"text": "bar", "id": 1}],
+    )
+    assert len(table) == 2
+    assert table.count_rows() == 2
+    assert table.count_rows(filter="text='bar'") == 1