fix(python): reject unsupported index accelerators

python/python/lancedb/index.py

@@ -314,8 +314,7 @@ class HnswPq:
     m: int = 20
     ef_construction: int = 300
     target_partition_size: Optional[int] = None
-    # Name of the accelerator ("cuda" or "mps") to use for IVF training. When set,
-    # create_index() dispatches to pylance to build the index on the accelerator.
+    # Reserved for future accelerator support. create_index() currently raises if set.
     accelerator: Optional[str] = None
 
 
@@ -422,8 +421,7 @@ class HnswSq:
     m: int = 20
     ef_construction: int = 300
     target_partition_size: Optional[int] = None
-    # Name of the accelerator ("cuda" or "mps") to use for IVF training. When set,
-    # create_index() dispatches to pylance to build the index on the accelerator.
+    # Reserved for future accelerator support. create_index() currently raises if set.
     accelerator: Optional[str] = None
 
 
@@ -618,8 +616,7 @@ class IvfFlat:
     max_iterations: int = 50
     sample_rate: int = 256
     target_partition_size: Optional[int] = None
-    # Name of the accelerator ("cuda" or "mps") to use for IVF training. When set,
-    # create_index() dispatches to pylance to build the index on the accelerator.
+    # Reserved for future accelerator support. create_index() currently raises if set.
     accelerator: Optional[str] = None
 
 
@@ -651,8 +648,7 @@ class IvfSq:
     max_iterations: int = 50
     sample_rate: int = 256
     target_partition_size: Optional[int] = None
-    # Name of the accelerator ("cuda" or "mps") to use for IVF training. When set,
-    # create_index() dispatches to pylance to build the index on the accelerator.
+    # Reserved for future accelerator support. create_index() currently raises if set.
     accelerator: Optional[str] = None
 
 
@@ -840,8 +836,7 @@ class IvfRq:
     max_iterations: int = 50
     sample_rate: int = 256
     target_partition_size: Optional[int] = None
-    # Name of the accelerator ("cuda" or "mps") to use for IVF training. When set,
-    # create_index() dispatches to pylance to build the index on the accelerator.
+    # Reserved for future accelerator support. create_index() currently raises if set.
     accelerator: Optional[str] = None
 
 

python/python/lancedb/remote/table.py

@@ -68,6 +68,14 @@ from ..table import AsyncTable, BlobMode, Branches, IndexStatistics, Query, Tabl
 from ..types import BaseTokenizerType
 
 
+def _reject_index_accelerator(
+    config: Optional[IndexConfigType] = None,
+    accelerator: Optional[str] = None,
+) -> None:
+    if accelerator is not None or getattr(config, "accelerator", None) is not None:
+        raise ValueError("Index accelerators are not supported on LanceDB Cloud.")
+
+
 class RemoteTable(Table):
     def __init__(
         self,
@@ -457,6 +465,8 @@ class RemoteTable(Table):
         ...     "l2", vector_column_name="vector"
         ... )
         """
+        _reject_index_accelerator(config, accelerator)
+
         # Detect whether this is a legacy API call
         is_legacy = self._is_legacy_create_index_call(
             metric,
@@ -484,12 +494,6 @@ class RemoteTable(Table):
 
             column = vector_column_name
 
-            if accelerator is not None:
-                logging.warning(
-                    "GPU accelerator is not yet supported on LanceDB cloud."
-                    "If you have 100M+ vectors to index,"
-                    "please contact us at contact@lancedb.com"
-                )
             if replace is not None:
                 logging.warning(
                     "replace is not supported on LanceDB cloud."
@@ -557,6 +561,8 @@ class RemoteTable(Table):
         The job may already be complete when returned; callers must not assume
         the index exists until :meth:`Job.wait` returns.
         """
+        _reject_index_accelerator(config)
+
         return Job(
             LOOP.run(
                 self._table.create_index_async(

python/python/lancedb/table.py

@@ -214,14 +214,7 @@ IndexConfigType = Union[
 # Known distance metrics for legacy API detection
 KNOWN_METRICS = {"l2", "cosine", "dot", "hamming"}
 
-_PYLANCE_ACCELERATED_INDEX_TYPES = {
-    IvfFlat: "IVF_FLAT",
-    IvfSq: "IVF_SQ",
-    IvfPq: "IVF_PQ",
-    IvfRq: "IVF_RQ",
-    HnswPq: "IVF_HNSW_PQ",
-    HnswSq: "IVF_HNSW_SQ",
-}
+_PYLANCE_ACCELERATED_INDEX_TYPE = "IVF_PQ"
 
 
 def _pylance_accelerated_index_options(
@@ -237,10 +230,15 @@ def _pylance_accelerated_index_options(
         return None
 
     if index_type is None:
-        index_type = _PYLANCE_ACCELERATED_INDEX_TYPES.get(type(config))
-    if index_type is None:
+        index_type = (
+            _PYLANCE_ACCELERATED_INDEX_TYPE
+            if isinstance(config, IvfPq)
+            else type(config).__name__
+        )
+    if index_type.upper() != _PYLANCE_ACCELERATED_INDEX_TYPE:
         raise ValueError(
-            f"Index type {type(config).__name__} does not support an accelerator"
+            f"Index type {index_type} does not support an accelerator; "
+            f"only {_PYLANCE_ACCELERATED_INDEX_TYPE} supports acceleration"
         )
 
     return {

python/python/tests/test_remote_db.py

@@ -875,6 +875,25 @@ def test_remote_create_index_async_returns_job():
         job.cancel()
 
 
+def test_remote_create_index_rejects_accelerator():
+    from lancedb.index import IvfPq
+    from lancedb.remote.table import RemoteTable
+
+    inner = MagicMock()
+    inner.name = "test"
+    table = RemoteTable(inner, "dev")
+
+    with pytest.raises(ValueError, match="not supported on LanceDB Cloud"):
+        table.create_index(accelerator="mps")
+    with pytest.raises(ValueError, match="not supported on LanceDB Cloud"):
+        table.create_index("vector", config=IvfPq(accelerator="mps"))
+    with pytest.raises(ValueError, match="not supported on LanceDB Cloud"):
+        table.create_index_async("vector", config=IvfPq(accelerator="mps"))
+
+    inner.create_index.assert_not_called()
+    inner.create_index_async.assert_not_called()
+
+
 def test_remote_job_wait_raises_on_failure():
     from lancedb.exceptions import JobFailedError
     from lancedb.index import BTree

python/python/tests/test_table.py

@@ -14,7 +14,17 @@ from unittest.mock import AsyncMock, MagicMock, patch
 
 import lancedb
 from lancedb.dependencies import _PANDAS_AVAILABLE
-from lancedb.index import BTree, FTS, HnswFlat, HnswPq, HnswSq, IvfPq
+from lancedb.index import (
+    BTree,
+    FTS,
+    HnswFlat,
+    HnswPq,
+    HnswSq,
+    IvfFlat,
+    IvfPq,
+    IvfRq,
+    IvfSq,
+)
 import numpy as np
 import polars as pl
 import pyarrow as pa
@@ -1455,6 +1465,51 @@ def test_create_index_dispatches_mps_to_pylance(mem_db: DBConnection):
     checkout_latest.assert_called_once_with()
 
 
+@pytest.mark.parametrize(
+    "config",
+    [
+        IvfFlat(accelerator="mps"),
+        IvfSq(accelerator="mps"),
+        IvfRq(accelerator="mps"),
+        HnswPq(accelerator="mps"),
+        HnswSq(accelerator="mps"),
+    ],
+)
+def test_create_index_rejects_unsupported_accelerated_format(
+    mem_db: DBConnection, config
+):
+    table = mem_db.create_table(
+        "unsupported_accelerator",
+        data=[{"vector": [3.1, 4.1]}, {"vector": [5.9, 26.5]}],
+    )
+
+    with (
+        patch.object(table, "to_lance") as to_lance,
+        pytest.raises(ValueError, match="only IVF_PQ supports acceleration"),
+    ):
+        table.create_index("vector", config=config)
+
+    to_lance.assert_not_called()
+
+
+def test_legacy_create_index_rejects_unsupported_accelerated_format(
+    mem_db: DBConnection,
+):
+    table = mem_db.create_table(
+        "unsupported_legacy_accelerator",
+        data=[{"vector": [3.1, 4.1]}, {"vector": [5.9, 26.5]}],
+    )
+
+    with (
+        pytest.warns(DeprecationWarning, match="create_index"),
+        patch.object(table, "to_lance") as to_lance,
+        pytest.raises(ValueError, match="only IVF_PQ supports acceleration"),
+    ):
+        table.create_index(index_type="IVF_FLAT", accelerator="mps")
+
+    to_lance.assert_not_called()
+
+
 @pytest.mark.asyncio
 async def test_async_create_index_dispatches_mps_to_pylance():
     inner = MagicMock()
@@ -1494,6 +1549,22 @@ async def test_async_create_index_dispatches_mps_to_pylance():
     inner.checkout_latest.assert_awaited_once_with()
 
 
+@pytest.mark.asyncio
+async def test_async_create_index_rejects_unsupported_accelerated_format():
+    inner = MagicMock()
+    inner._is_native.return_value = True
+    table = AsyncTable(inner)
+
+    with (
+        patch.object(table, "to_lance", AsyncMock()) as to_lance,
+        pytest.raises(ValueError, match="only IVF_PQ supports acceleration"),
+    ):
+        await table.create_index("vector", config=IvfFlat(accelerator="mps"))
+
+    to_lance.assert_not_awaited()
+    inner.create_index.assert_not_called()
+
+
 @pytest.mark.asyncio
 async def test_async_background_index_rejects_accelerator():
     inner = MagicMock()