Add UpcastIndex trait

src/index/flat.rs

@@ -151,11 +151,21 @@ impl_concurrent_index!(FlatIndexImpl);
 #[cfg(test)]
 mod tests {
     use super::FlatIndexImpl;
-    use crate::index::{index_factory, ConcurrentIndex, FromInnerPtr, Idx, Index, NativeIndex};
+    use crate::index::{
+        index_factory, ConcurrentIndex, FromInnerPtr, Idx, Index, NativeIndex, UpcastIndex,
+    };
     use crate::metric::MetricType;
 
     const D: u32 = 8;
 
+    #[test]
+    fn flat_index_from_upcast() {
+        let index = FlatIndexImpl::new_l2(D).unwrap();
+
+        let index_impl = index.upcast();
+        assert_eq!(index_impl.d(), D);
+    }
+
     #[test]
     fn flat_index_from_cast() {
         let mut index = index_factory(8, "Flat", MetricType::L2).unwrap();

src/index/ivf_flat.rs

@@ -166,7 +166,7 @@ mod tests {
 
     use super::IVFFlatIndexImpl;
     use crate::index::flat::FlatIndexImpl;
-    use crate::index::{index_factory, ConcurrentIndex, Idx, Index};
+    use crate::index::{index_factory, ConcurrentIndex, Idx, Index, UpcastIndex};
     use crate::MetricType;
 
     const D: u32 = 8;
@@ -286,4 +286,15 @@ mod tests {
         assert_eq!(index.is_trained(), true);
         assert_eq!(index.ntotal(), 5);
     }
+
+    #[test]
+    fn index_upcast() {
+        let q = FlatIndexImpl::new_l2(D).unwrap();
+        let index = IVFFlatIndexImpl::new_l2(q, D, 1).unwrap();
+        assert_eq!(index.d(), D);
+        assert_eq!(index.ntotal(), 0);
+
+        let index_impl = index.upcast();
+        assert_eq!(index_impl.d(), D);
+    }
 }

src/index/mod.rs

@@ -17,7 +17,7 @@ use crate::selector::IdSelector;
 use std::ffi::CString;
 use std::fmt::{self, Display, Formatter, Write};
 use std::os::raw::c_uint;
-use std::ptr;
+use std::{mem, ptr};
 
 use faiss_sys::*;
 
@@ -467,6 +467,19 @@ impl TryFromInnerPtr for IndexImpl {
     }
 }
 
+pub trait UpcastIndex: NativeIndex {
+    fn upcast(self) -> IndexImpl;
+}
+
+impl<NI: NativeIndex> UpcastIndex for NI {
+    fn upcast(self) -> IndexImpl {
+        let inner_ptr = self.inner_ptr();
+        mem::forget(self);
+
+        unsafe { IndexImpl::from_inner_ptr(inner_ptr) }
+    }
+}
+
 impl_native_index!(IndexImpl);
 
 impl_native_index_clone!(IndexImpl);

src/index/pretransform.rs

@@ -297,7 +297,7 @@ mod tests {
     const D: u32 = 8;
 
     #[test]
-    fn pre_transform_index_from_cast() {
+    fn pre_transform_index_from_cast_upcast() {
         let mut index = index_factory(D, "PCA4,Flat", MetricType::L2).unwrap();
 
         let some_data = &[
@@ -315,6 +315,11 @@ mod tests {
         assert_eq!(index.is_trained(), true);
         assert_eq!(index.ntotal(), 5);
         assert_eq!(index.d(), 8);
+
+        let index_impl = index.upcast();
+        assert_eq!(index_impl.is_trained(), true);
+        assert_eq!(index_impl.ntotal(), 5);
+        assert_eq!(index_impl.d(), 8);
     }
 
     #[test]

src/index/refine_flat.rs

@@ -270,7 +270,7 @@ where
 #[cfg(test)]
 mod tests {
     use super::RefineFlatIndexImpl;
-    use crate::index::{flat::FlatIndexImpl, ConcurrentIndex, Idx, Index};
+    use crate::index::{flat::FlatIndexImpl, ConcurrentIndex, Idx, Index, UpcastIndex};
 
     const D: u32 = 8;
 
@@ -315,4 +315,16 @@ mod tests {
         refine.reset().unwrap();
         assert_eq!(refine.ntotal(), 0);
     }
+
+    #[test]
+    fn refine_flat_index_upcast() {
+        let index = FlatIndexImpl::new_l2(D).unwrap();
+        assert_eq!(index.d(), D);
+        assert_eq!(index.ntotal(), 0);
+
+        let refine = RefineFlatIndexImpl::new(index).unwrap();
+
+        let index_impl = refine.upcast();
+        assert_eq!(index_impl.d(), D);
+    }
 }

src/index/scalar_quantizer.rs

@@ -491,7 +491,7 @@ impl IndexImpl {
 #[cfg(test)]
 mod tests {
     use super::{IVFScalarQuantizerIndexImpl, QuantizerType, ScalarQuantizerIndexImpl};
-    use crate::index::{flat, index_factory, ConcurrentIndex, Idx, Index};
+    use crate::index::{flat, index_factory, ConcurrentIndex, Idx, Index, UpcastIndex};
     use crate::metric::MetricType;
 
     const D: u32 = 8;
@@ -679,4 +679,16 @@ mod tests {
         assert_eq!(index.is_trained(), true);
         assert_eq!(index.ntotal(), 5);
     }
+
+    #[test]
+    fn ivf_sq_index_upcast() {
+        let quantizer = flat::FlatIndex::new_l2(D).unwrap();
+        let index =
+            IVFScalarQuantizerIndexImpl::new_l2(quantizer, D, QuantizerType::QT_fp16, 1).unwrap();
+        assert_eq!(index.d(), D);
+        assert_eq!(index.ntotal(), 0);
+
+        let index_impl = index.upcast();
+        assert_eq!(index_impl.d(), D);
+    }
 }