Keep the mapped CSR and the mapped index in separate members

nsparse/disk_seismic_index_base.cpp

@@ -194,9 +194,9 @@ void DiskSeismicIndexBase::load_mapped_payload(MmapCursor* cursor,
     // width mismatch before we commit.
     validate_mapped_payload();
 
-    // mapped_file_ last: the summaries and the forward index borrow from it,
+    // index_mapping_ last: the summaries and the forward index borrow from it,
     // and moving it does not move the mapping.
-    mapped_file_ = std::move(mapped);
+    index_mapping_ = std::move(mapped);
 }
 
 }  // namespace nsparse

nsparse/inverted_index.cpp

@@ -278,7 +278,7 @@ void InvertedIndex::build() {
     vectors_.reset();
     // The posting lists own their entries, so nothing borrows from a mapped CSR
     // once the vectors are gone.
-    mapped_file_.close();
+    csr_mapping_.close();
 
     // Posting lists are already sorted by doc_id because
     // build_inverted_lists iterates documents in ascending order.
@@ -471,14 +471,14 @@ InvertedIndex* InvertedIndex::mmap_index(const IndexHeader& header,
     throw_if_scores_are_incomplete(*lists, scores_size);
 
     // Committed only once everything parsed, so a corrupt file cannot leave a
-    // half-mapped index behind. mapped_file_ last: the arrays above borrow from
-    // it, and moving it does not move the mapping itself.
+    // half-mapped index behind. index_mapping_ last: the arrays above borrow
+    // from it, and moving it does not move the mapping itself.
     index->num_vectors_ = num_vectors;
     index->max_term_scores_ = std::move(scores);
     if (lists->size() > 0) {
         index->inverted_lists_ = std::move(lists);
     }
-    index->mapped_file_ = std::move(mmap_file);
+    index->index_mapping_ = std::move(mmap_file);
     return index.release();
 }
 

nsparse/mmap_index.h

@@ -51,21 +51,24 @@ class MmapIndex : public Index {
     }
 
 protected:
-    // The mapping borrowed buffers point into: a native CSR file via read_csr,
-    // or a serialized index file. Those sources are mutually exclusive, so one
-    // member serves both.
+    // The two mappings borrowed buffers can point into, kept apart because they
+    // are populated by unrelated paths and released independently: a native CSR
+    // corpus opened by read_csr's mapped residency, and a serialized index file
+    // opened by a derived mmap_index.
     //
-    // Borrowers do not reference it, so it must outlive them. Members are
-    // destroyed in reverse declaration order, hence this one first: do not
-    // reorder it past anything that borrows from it.
-    MmapFile mapped_file_;
+    // Borrowers do not reference either one, so both must outlive them. Members
+    // are destroyed in reverse declaration order, hence these first: do not
+    // reorder them past anything that borrows from them.
+    MmapFile csr_mapping_;
+    MmapFile index_mapping_;
 
     // Either residency: buffers owned when built or deserialized, borrowed from
-    // mapped_file_ when mapped. get_vectors() cannot tell the two apart.
+    // csr_mapping_ or index_mapping_ when mapped. get_vectors() cannot tell the
+    // cases apart.
     std::unique_ptr<SparseVectors> vectors_;
 
     // A batched build's spill, which its posting lists borrow from. Separate
-    // from mapped_file_ because the two coexist: the corpus may itself be a
+    // from csr_mapping_ because the two coexist: the corpus may itself be a
     // mapping vectors_ is still borrowing from.
     //
     // Its borrowers live in the derived class, destroyed before base members,
@@ -155,7 +158,7 @@ class MmapIndex : public Index {
                 nnz_size * element_size));
 
         // Committed last, so a rejected file leaves the index untouched.
-        mapped_file_ = std::move(file);
+        csr_mapping_ = std::move(file);
         vectors_ = std::move(vectors);
     }
 };

nsparse/seismic_index.cpp

@@ -317,13 +317,13 @@ SeismicIndex* SeismicIndex::mmap_index(const IndexHeader& header,
     inv_list_writer.mmap_deserialize(&cursor);
 
     // Committed only once everything parsed, so a corrupt file cannot leave a
-    // half-mapped index behind. mapped_file_ last: the arrays above borrow from
-    // it, and moving it does not move the mapping itself.
+    // half-mapped index behind. index_mapping_ last: the arrays above borrow
+    // from it, and moving it does not move the mapping itself.
     index->clustered_inverted_lists = std::move(inv_list_writer.release());
     if (vectors->num_vectors() > 0) {
         index->vectors_ = std::move(vectors);
     }
-    index->mapped_file_ = std::move(mmap_file);
+    index->index_mapping_ = std::move(mmap_file);
     return index.release();
 }
 }  // namespace nsparse

nsparse/seismic_scalar_quantized_index.cpp

@@ -400,14 +400,14 @@ SeismicScalarQuantizedIndex* SeismicScalarQuantizedIndex::mmap_index(
     inv_list_writer.mmap_deserialize(&cursor);
 
     // Committed only once everything parsed, so a corrupt file cannot leave a
-    // half-mapped index behind. mapped_file_ last: the arrays above borrow from
-    // it, and moving it does not move the mapping itself.
+    // half-mapped index behind. index_mapping_ last: the arrays above borrow
+    // from it, and moving it does not move the mapping itself.
     index->sq_ = sq;
     index->clustered_inverted_lists = std::move(inv_list_writer.release());
     if (vectors->num_vectors() > 0) {
         index->vectors_ = std::move(vectors);
     }
-    index->mapped_file_ = std::move(mmap_file);
+    index->index_mapping_ = std::move(mmap_file);
     return index.release();
 }