feat: allow prefiltering with index (#610)

Support for prefiltering with an index was added in lance version 0.8.7.
We can remove the lancedb check that prevents this. Closes #261

python/tests/test_db.py

@@ -287,3 +287,27 @@ def test_replace_index(tmp_path):
         num_sub_vectors=4,
         replace=True,
     )
+
+
+def test_prefilter_with_index(tmp_path):
+    db = lancedb.connect(uri=tmp_path)
+    data = [
+        {"vector": np.random.rand(128), "item": "foo", "price": float(i)}
+        for i in range(1000)
+    ]
+    sample_key = data[100]["vector"]
+    table = db.create_table(
+        "test",
+        data,
+    )
+    table.create_index(
+        num_partitions=2,
+        num_sub_vectors=4,
+    )
+    table = (
+        table.search(sample_key)
+        .where("price == 500", prefilter=True)
+        .limit(5)
+        .to_arrow()
+    )
+    assert table.num_rows == 1