Update arg check to raise exception is index build args don't match r…

…equest index

src/tests/test_collection.py

@@ -626,44 +626,83 @@ def test_index_build_args(client: vecs.Client) -> None:
     bar.upsert([("a", [1, 2, 3, 4], {})])
 
     # Test that default value for nlists is used in absence of index build args
-    bar.create_index(method="ivfflat")  # type: ignore
-    [nlists] = [i for i in bar.index.split("_") if i.startswith("nl")]
-    assert int(nlists.strip("nl")) == 30
-
-    # Test that default value for nlists is used when when incorrect index build
-    # args are supplied
-    bar.create_index(method=IndexMethod.ivfflat, index_arguments=IndexArgsHNSW(), replace=True)  # type: ignore
+    bar.create_index(method="ivfflat")
     [nlists] = [i for i in bar.index.split("_") if i.startswith("nl")]
     assert int(nlists.strip("nl")) == 30
 
     # Test nlists is honored when supplied
-    bar.create_index(method=IndexMethod.ivfflat, index_arguments=IndexArgsIVFFlat(n_lists=123), replace=True)  # type: ignore
+    bar.create_index(
+        method=IndexMethod.ivfflat,
+        index_arguments=IndexArgsIVFFlat(n_lists=123),
+        replace=True,
+    )
     [nlists] = [i for i in bar.index.split("_") if i.startswith("nl")]
     assert int(nlists.strip("nl")) == 123
 
     # Test that default values for m and ef_construction are used in absence of
     # index build args
-    bar.create_index(method="hnsw", replace=True)  # type: ignore
+    bar.create_index(method="hnsw", replace=True)
     [m] = [i for i in bar.index.split("_") if i.startswith("m")]
     [ef_construction] = [i for i in bar.index.split("_") if i.startswith("efc")]
     assert int(m.strip("m")) == 16
     assert int(ef_construction.strip("efc")) == 64
 
-    # Test that the default values for m and ef_construction are used when
-    # incorrect index build args are supplied
-    bar.create_index(method="hnsw", index_arguments=IndexArgsIVFFlat(n_lists=123), replace=True)  # type: ignore
+    # Test m and ef_construction is honored when supplied
+    bar.create_index(
+        method="hnsw",
+        index_arguments=IndexArgsHNSW(m=8, ef_construction=123),
+        replace=True,
+    )
+    [m] = [i for i in bar.index.split("_") if i.startswith("m")]
+    [ef_construction] = [i for i in bar.index.split("_") if i.startswith("efc")]
+    assert int(m.strip("m")) == 8
+    assert int(ef_construction.strip("efc")) == 123
+
+    # Test m is honored and ef_construction is default when _only_ m is supplied
+    bar.create_index(method="hnsw", index_arguments=IndexArgsHNSW(m=8), replace=True)
     [m] = [i for i in bar.index.split("_") if i.startswith("m")]
     [ef_construction] = [i for i in bar.index.split("_") if i.startswith("efc")]
-    assert int(m.strip("m")) == 16
+    assert int(m.strip("m")) == 8
     assert int(ef_construction.strip("efc")) == 64
 
-    # Test m and ef_construnction is honored when supplied
-    bar.create_index(method="hnsw", index_arguments=IndexArgsHNSW(m=12, ef_construction=123), replace=True)  # type: ignore
+    # Test m is default and ef_construction is honoured when _only_
+    # ef_construction is supplied
+    bar.create_index(
+        method="hnsw", index_arguments=IndexArgsHNSW(ef_construction=123), replace=True
+    )
     [m] = [i for i in bar.index.split("_") if i.startswith("m")]
     [ef_construction] = [i for i in bar.index.split("_") if i.startswith("efc")]
-    assert int(m.strip("m")) == 12
+    assert int(m.strip("m")) == 16
     assert int(ef_construction.strip("efc")) == 123
 
+    # Test that exception is raised when index build args don't match
+    # the requested index type
+    with pytest.raises(vecs.exc.ArgError):
+        bar.create_index(
+            method=IndexMethod.ivfflat, index_arguments=IndexArgsHNSW(), replace=True
+        )
+    with pytest.raises(vecs.exc.ArgError):
+        bar.create_index(
+            method=IndexMethod.hnsw,
+            index_arguments=IndexArgsIVFFlat(n_lists=123),
+            replace=True,
+        )
+
+    # Test that excpetion is raised index build args are supplied by the
+    # IndexMethod.auto index is specified
+    with pytest.raises(vecs.exc.ArgError):
+        bar.create_index(
+            method=IndexMethod.auto,
+            index_arguments=IndexArgsIVFFlat(n_lists=123),
+            replace=True,
+        )
+    with pytest.raises(vecs.exc.ArgError):
+        bar.create_index(
+            method=IndexMethod.auto,
+            index_arguments=IndexArgsHNSW(),
+            replace=True,
+        )
+
 
 def test_cosine_index_query(client: vecs.Client) -> None:
     dim = 4

src/vecs/collection.py

@@ -690,9 +690,30 @@ def create_index(
             ArgError: If an invalid index method is used, or if *replace* is False and an index already exists.
         """
 
-        if not method in (IndexMethod.ivfflat, IndexMethod.hnsw, IndexMethod.auto):
+        if method not in (IndexMethod.ivfflat, IndexMethod.hnsw, IndexMethod.auto):
             raise ArgError("invalid index method")
 
+        if index_arguments:
+            # Disallow case where user submits index arguments but uses the
+            # IndexMethod.auto index (index build arguments should only be
+            # used with a specific index)
+            if method == IndexMethod.auto:
+                raise ArgError(
+                    "Index build parameters are not allowed when using the IndexMethod.auto index."
+                )
+            # Disallow case where user specifies one index type but submits
+            # index build arguments for the other index type
+            if (
+                isinstance(index_arguments, IndexArgsHNSW)
+                and method != IndexMethod.hnsw
+            ) or (
+                isinstance(index_arguments, IndexArgsIVFFlat)
+                and method != IndexMethod.ivfflat
+            ):
+                raise ArgError(
+                    f"{index_arguments.__class__.__name__} build parameters were supplied but {method} index was specified."
+                )
+
         if method == IndexMethod.auto:
             if self.client._supports_hnsw():
                 method = IndexMethod.hnsw
@@ -704,24 +725,6 @@ def create_index(
                 "HNSW Unavailable. Upgrade your pgvector installation to > 0.5.0 to enable HNSW support"
             )
 
-        # Catch case where use submits index build args for one index type but
-        # method defines a different index type.
-        if index_arguments and (
-            (isinstance(index_arguments, IndexArgsHNSW) and method != IndexMethod.hnsw)
-            or (
-                isinstance(index_arguments, IndexArgsIVFFlat)
-                and method != IndexMethod.ivfflat
-            )
-        ):
-            warnings.warn(
-                UserWarning(
-                    f"{index_arguments.__class__.__name__} build parameters were supplied but {method} index was specified. Default parameters for {method} index will be used instead."
-                )
-            )
-            # set index_arguments to None in order to instantiate
-            # with the default values later
-            index_arguments = None
-
         ops = INDEX_MEASURE_TO_OPS.get(measure)
         if ops is None:
             raise ArgError("Unknown index measure")