[BP] MB-58893: Handle dropped collections when computing data size for filter

When calculating the total size of all collections referenced by the
filter, handle the case where the collection is not found in the
manifest.

Change-Id: I44a4aacba111d0e731dcf043a9d51c8e316668d3
Reviewed-on: https://review.couchbase.org/c/kv_engine/+/200210
Well-Formed: Restriction Checker
Reviewed-by: Vesko Karaganev <[email protected]>
Tested-by: Jim Walker <[email protected]>

Author: veselink1

engines/ep/src/collections/vbucket_filter.cc

@@ -505,6 +505,10 @@ Filter::CollectionSizeStats Filter::getSizeStats(
     for (auto [cid, sid] : filter) {
         (void)sid;
         const auto stats = manifest.lock(cid);
+        if (!stats.valid()) {
+            // The collection has been dropped, so we don't increment the stats.
+            continue;
+        }
         colItemCount += stats.getItemCount();
         colDiskSize += stats.getDiskSize();
     }

engines/ep/src/collections/vbucket_filter.h

@@ -230,7 +230,8 @@ class Filter {
     };
 
     /**
-     * Get aggregated collection stats for all collections in the filter.
+     * Get aggregated collection stats for all collections in the filter. Any
+     * collections which do not exist are ignored from the aggregate.
      */
     CollectionSizeStats getSizeStats(const Manifest& manifest) const;
 

engines/ep/tests/module_tests/collections/filter_test.cc

@@ -1240,6 +1240,25 @@ TEST_F(CollectionsVBFilterTest, snappy_event) {
                             0}));
 }
 
+TEST_F(CollectionsVBFilterTest, size_stats_for_dropped_collection) {
+    cm.add(CollectionEntry::fruit);
+    auto m = makeManifest(cm);
+    vbm.update(*vb, m);
+
+    // Filter by fruit collection.
+    std::string filterJson = R"({"collections":["9"]})";
+    std::optional<std::string_view> filterManifest{filterJson};
+    Collections::VB::Filter filter(filterManifest, vbm, *cookie, *engine);
+
+    cm.remove(CollectionEntry::fruit);
+    m = makeManifest(cm);
+    vbm.update(*vb, m);
+
+    // Make sure getSizeStats does not crash due to the collection in the
+    // filter having been dropped.
+    filter.getSizeStats(vbm);
+}
+
 class CollectionsVBFilterAccessControlTest : public CollectionsVBFilterTest {
     void TearDown() override {
         MockCookie::setCheckPrivilegeFunction({});