Support Selector for IDMap (facebookresearch#2848)

Summary:
Pull Request resolved: facebookresearch#2848

Add selector support for IDMap wrapped indices.
Caveat: this requires to wrap the IDSelector with another selector. Since the params are const, the const is casted away.

This is a problem if the same params are used from multiple execution threads with different selectors. However, this seems rare enough to take the risk.

Reviewed By: alexanderguzhva

Differential Revision: D45598823

fbshipit-source-id: ec23465c13f1f8273a6a46f9aa869ccae2cdb79c

Author: mdouze

faiss/IndexIDMap.cpp

@@ -16,7 +16,6 @@
 
 #include <faiss/impl/AuxIndexStructures.h>
 #include <faiss/impl/FaissAssert.h>
-#include <faiss/impl/IDSelector.h>
 #include <faiss/utils/Heap.h>
 #include <faiss/utils/WorkerThread.h>
 
@@ -71,6 +70,27 @@ void IndexIDMapTemplate<IndexT>::add_with_ids(
     this->ntotal = index->ntotal;
 }
 
+namespace {
+
+/// RAII object to reset the IDSelector in the params object
+struct ScopedSelChange {
+    SearchParameters* params = nullptr;
+    IDSelector* old_sel = nullptr;
+
+    void set(SearchParameters* params, IDSelector* new_sel) {
+        this->params = params;
+        old_sel = params->sel;
+        params->sel = new_sel;
+    }
+    ~ScopedSelChange() {
+        if (params) {
+            params->sel = old_sel;
+        }
+    }
+};
+
+} // namespace
+
 template <typename IndexT>
 void IndexIDMapTemplate<IndexT>::search(
         idx_t n,
@@ -79,9 +99,26 @@ void IndexIDMapTemplate<IndexT>::search(
         typename IndexT::distance_t* distances,
         idx_t* labels,
         const SearchParameters* params) const {
-    FAISS_THROW_IF_NOT_MSG(
-            !params, "search params not supported for this index");
-    index->search(n, x, k, distances, labels);
+    IDSelectorTranslated this_idtrans(this->id_map, nullptr);
+    ScopedSelChange sel_change;
+
+    if (params && params->sel) {
+        auto idtrans = dynamic_cast<const IDSelectorTranslated*>(params->sel);
+
+        if (!idtrans) {
+            /*
+            FAISS_THROW_IF_NOT_MSG(
+                    idtrans,
+                    "IndexIDMap requires an IDSelectorTranslated on input");
+            */
+            // then make an idtrans and force it into the SearchParameters
+            // (hence the const_cast)
+            auto params_non_const = const_cast<SearchParameters*>(params);
+            this_idtrans.sel = params->sel;
+            sel_change.set(params_non_const, &this_idtrans);
+        }
+    }
+    index->search(n, x, k, distances, labels, params);
     idx_t* li = labels;
 #pragma omp parallel for
     for (idx_t i = 0; i < n * k; i++) {
@@ -106,26 +143,10 @@ void IndexIDMapTemplate<IndexT>::range_search(
     }
 }
 
-namespace {
-
-struct IDTranslatedSelector : IDSelector {
-    const std::vector<int64_t>& id_map;
-    const IDSelector& sel;
-    IDTranslatedSelector(
-            const std::vector<int64_t>& id_map,
-            const IDSelector& sel)
-            : id_map(id_map), sel(sel) {}
-    bool is_member(idx_t id) const override {
-        return sel.is_member(id_map[id]);
-    }
-};
-
-} // namespace
-
 template <typename IndexT>
 size_t IndexIDMapTemplate<IndexT>::remove_ids(const IDSelector& sel) {
     // remove in sub-index first
-    IDTranslatedSelector sel2(id_map, sel);
+    IDSelectorTranslated sel2(id_map, &sel);
     size_t nremove = index->remove_ids(sel2);
 
     int64_t j = 0;

faiss/IndexIDMap.h

@@ -9,6 +9,7 @@
 
 #include <faiss/Index.h>
 #include <faiss/IndexBinary.h>
+#include <faiss/impl/IDSelector.h>
 
 #include <unordered_map>
 #include <vector>
@@ -102,4 +103,25 @@ struct IndexIDMap2Template : IndexIDMapTemplate<IndexT> {
 using IndexIDMap2 = IndexIDMap2Template<Index>;
 using IndexBinaryIDMap2 = IndexIDMap2Template<IndexBinary>;
 
+// IDSelector that translates the ids using an IDMap
+struct IDSelectorTranslated : IDSelector {
+    const std::vector<int64_t>& id_map;
+    const IDSelector* sel;
+
+    IDSelectorTranslated(
+            const std::vector<int64_t>& id_map,
+            const IDSelector* sel)
+            : id_map(id_map), sel(sel) {}
+
+    IDSelectorTranslated(IndexBinaryIDMap& index_idmap, const IDSelector* sel)
+            : id_map(index_idmap.id_map), sel(sel) {}
+
+    IDSelectorTranslated(IndexIDMap& index_idmap, const IDSelector* sel)
+            : id_map(index_idmap.id_map), sel(sel) {}
+
+    bool is_member(idx_t id) const override {
+        return sel->is_member(id_map[id]);
+    }
+};
+
 } // namespace faiss

faiss/python/__init__.py

@@ -192,6 +192,7 @@ def replacement_function(*args):
 add_ref_in_constructor(IDSelectorAnd, slice(2))
 add_ref_in_constructor(IDSelectorOr, slice(2))
 add_ref_in_constructor(IDSelectorXOr, slice(2))
+add_ref_in_constructor(IDSelectorTranslated, slice(2))
 
 # seems really marginal...
 # remove_ref_from_method(IndexReplicas, 'removeIndex', 0)

faiss/python/swigfaiss.swig

@@ -494,11 +494,6 @@ void gpu_sync_all_devices()
 %template(IndexBinaryReplicas) faiss::IndexReplicasTemplate<faiss::IndexBinary>;
 
 %include  <faiss/MetaIndexes.h>
-%include  <faiss/IndexIDMap.h>
-%template(IndexIDMap) faiss::IndexIDMapTemplate<faiss::Index>;
-%template(IndexBinaryIDMap) faiss::IndexIDMapTemplate<faiss::IndexBinary>;
-%template(IndexIDMap2) faiss::IndexIDMap2Template<faiss::Index>;
-%template(IndexBinaryIDMap2) faiss::IndexIDMap2Template<faiss::IndexBinary>;
 
 %include  <faiss/IndexRowwiseMinMax.h>
 
@@ -513,6 +508,13 @@ void gpu_sync_all_devices()
 %include <faiss/impl/AuxIndexStructures.h>
 %include <faiss/impl/IDSelector.h>
 
+%include  <faiss/IndexIDMap.h>
+%template(IndexIDMap) faiss::IndexIDMapTemplate<faiss::Index>;
+%template(IndexBinaryIDMap) faiss::IndexIDMapTemplate<faiss::IndexBinary>;
+%template(IndexIDMap2) faiss::IndexIDMap2Template<faiss::Index>;
+%template(IndexBinaryIDMap2) faiss::IndexIDMap2Template<faiss::IndexBinary>;
+
+
 %include <faiss/utils/approx_topk/mode.h>
 
 #ifdef GPU_WRAPPER

tests/test_search_params.py

@@ -101,17 +101,17 @@ def do_test_id_selector(self, index_key, id_selector_type="batch", mt=faiss.METR
             sel = faiss.IDSelectorNot(faiss.IDSelectorBatch(inverse_subset))
         elif id_selector_type == "or":
             sel = faiss.IDSelectorOr(
-                faiss.IDSelectorBatch(lhs_subset), 
+                faiss.IDSelectorBatch(lhs_subset),
                 faiss.IDSelectorBatch(rhs_subset)
             )
         elif id_selector_type == "and":
             sel = faiss.IDSelectorAnd(
-                faiss.IDSelectorBatch(lhs_subset), 
+                faiss.IDSelectorBatch(lhs_subset),
                 faiss.IDSelectorBatch(rhs_subset)
             )
         elif id_selector_type == "xor":
             sel = faiss.IDSelectorXOr(
-                faiss.IDSelectorBatch(lhs_subset), 
+                faiss.IDSelectorBatch(lhs_subset),
                 faiss.IDSelectorBatch(rhs_subset)
             )
         else:
@@ -181,7 +181,7 @@ def test_Flat_id_bitmap(self):
 
     def test_Flat_id_not(self):
         self.do_test_id_selector("Flat", id_selector_type="not")
-    
+
     def test_Flat_id_or(self):
         self.do_test_id_selector("Flat", id_selector_type="or")
 
@@ -220,6 +220,41 @@ def do_test_id_selector_weak(self, index_key):
     def test_HSNW(self):
         self.do_test_id_selector_weak("HNSW")
 
+    def test_idmap(self):
+        ds = datasets.SyntheticDataset(32, 100, 100, 20)
+        rs = np.random.RandomState(123)
+        ids = rs.choice(10000, size=100, replace=False)
+        mask = ids % 2 == 0
+        index = faiss.index_factory(ds.d, "IDMap,SQ8")
+        index.train(ds.get_train())
+
+        # ref result
+        index.add_with_ids(ds.get_database()[mask], ids[mask])
+        Dref, Iref = index.search(ds.get_queries(), 10)
+
+        # with selector
+        index.reset()
+        index.add_with_ids(ds.get_database(), ids)
+
+        valid_ids = ids[mask]
+        sel = faiss.IDSelectorTranslated(
+            index, faiss.IDSelectorBatch(valid_ids))
+
+        Dnew, Inew = index.search(
+            ds.get_queries(), 10,
+            params=faiss.SearchParameters(sel=sel)
+        )
+        np.testing.assert_array_equal(Iref, Inew)
+        np.testing.assert_array_almost_equal(Dref, Dnew, decimal=5)
+
+        # let the IDMap::search add the translation...
+        Dnew, Inew = index.search(
+            ds.get_queries(), 10,
+            params=faiss.SearchParameters(sel=faiss.IDSelectorBatch(valid_ids))
+        )
+        np.testing.assert_array_equal(Iref, Inew)
+        np.testing.assert_array_almost_equal(Dref, Dnew, decimal=5)
+
 
 class TestSearchParams(unittest.TestCase):