feat: add create_index to the async python API (#1052)

This also refactors the rust lancedb index builder API (and,
correspondingly, the nodejs API)

python/python/tests/test_index.py

@@ -0,0 +1,61 @@
+from datetime import timedelta
+
+import pyarrow as pa
+import pytest
+import pytest_asyncio
+from lancedb import AsyncConnection, AsyncTable, connect_async
+from lancedb.index import BTree, IvfPq
+
+
+@pytest_asyncio.fixture
+async def db_async(tmp_path) -> AsyncConnection:
+    return await connect_async(tmp_path, read_consistency_interval=timedelta(seconds=0))
+
+
+def sample_fixed_size_list_array(nrows, dim):
+    vector_data = pa.array([float(i) for i in range(dim * nrows)], pa.float32())
+    return pa.FixedSizeListArray.from_arrays(vector_data, dim)
+
+
+DIM = 8
+NROWS = 256
+
+
+@pytest_asyncio.fixture
+async def some_table(db_async):
+    data = pa.Table.from_pydict(
+        {
+            "id": list(range(256)),
+            "vector": sample_fixed_size_list_array(NROWS, DIM),
+        }
+    )
+    return await db_async.create_table(
+        "some_table",
+        data,
+    )
+
+
+@pytest.mark.asyncio
+async def test_create_scalar_index(some_table: AsyncTable):
+    # Can create
+    await some_table.create_index("id")
+    # Can recreate if replace=True
+    await some_table.create_index("id", replace=True)
+    # Can't recreate if replace=False
+    with pytest.raises(RuntimeError, match="already exists"):
+        await some_table.create_index("id", replace=False)
+    # can also specify index type
+    await some_table.create_index("id", config=BTree())
+
+
+@pytest.mark.asyncio
+async def test_create_vector_index(some_table: AsyncTable):
+    # Can create
+    await some_table.create_index("vector")
+    # Can recreate if replace=True
+    await some_table.create_index("vector", replace=True)
+    # Can't recreate if replace=False
+    with pytest.raises(RuntimeError, match="already exists"):
+        await some_table.create_index("vector", replace=False)
+    # Can also specify index type
+    await some_table.create_index("vector", config=IvfPq(num_partitions=100))