Speed up transaction log parsing for queries

src/collection_notifications.cpp

@@ -267,45 +267,51 @@ void CollectionChangeBuilder::move_over(size_t row_ndx, size_t last_row)
         erase(row_ndx);
         return;
     }
-    move(last_row, row_ndx);
-    erase(row_ndx + 1);
-    return;
+
+    bool modified = modifications.contains(last_row);
+    modifications.erase_at(last_row);
+    if (modified)
+        modifications.add(row_ndx);
+    else
+        modifications.remove(row_ndx);
 
     bool updated_existing_move = false;
     for (size_t i = 0; i < moves.size(); ++i) {
         auto& move = moves[i];
-        REALM_ASSERT(move.to <= last_row);
-
+        // Remove moves to the row being deleted
         if (move.to == row_ndx) {
-            REALM_ASSERT(!updated_existing_move);
-            moves[i] = moves.back();
-            moves.pop_back();
+            moves.erase(moves.begin() + i);
             --i;
-            updated_existing_move = true;
+            continue;
         }
-        else if (move.to == last_row) {
-            REALM_ASSERT(!updated_existing_move);
-            move.to = row_ndx;
-            updated_existing_move = true;
-        }
-    }
-    if (!updated_existing_move) {
-        moves.push_back({last_row, row_ndx});
+        if (move.to != last_row)
+            continue;
+        REALM_ASSERT(!updated_existing_move);
+
+        // Collapse A -> B, B -> C into a single A -> C move
+        move.to = row_ndx;
+        updated_existing_move = true;
+
+        insertions.erase_at(last_row);
+        insertions.insert_at(row_ndx);
+        // Because this is a move, the unshifted source row has already been marked as deleted
     }
 
-    insertions.remove(row_ndx);
-    modifications.remove(row_ndx);
+    if (updated_existing_move)
+        return;
 
-    // not add_shifted() because unordered removal does not shift
-    // mixed ordered/unordered removal currently not supported
-    deletions.add(row_ndx);
-
-    if (modifications.contains(last_row)) {
-        modifications.remove(last_row);
-        modifications.add(row_ndx);
+    // Don't report deletions/moves if last_row is newly inserted
+    auto shifted_last_row = insertions.erase_and_unshift(last_row);
+    if (shifted_last_row != npos) {
+        shifted_last_row = deletions.add_shifted(shifted_last_row);
+        moves.push_back({shifted_last_row, row_ndx});
     }
 
-    insertions.add(row_ndx);
+    // Don't mark the moved-over row as deleted if it was a new insertion
+    if (!insertions.contains(row_ndx)) {
+        deletions.add_shifted(insertions.unshift(row_ndx));
+        insertions.add(row_ndx);
+    }
 }
 
 void CollectionChangeBuilder::verify()

src/index_set.cpp

@@ -385,13 +385,7 @@ size_t IndexSet::shift(size_t index) const
 size_t IndexSet::unshift(size_t index) const
 {
     REALM_ASSERT_DEBUG(!contains(index));
-    auto shifted = index;
-    for (auto range : m_ranges) {
-        if (range.first >= index)
-            break;
-        shifted -= std::min(range.second, index) - range.first;
-    }
-    return shifted;
+    return index - count(0, index);
 }
 
 void IndexSet::clear()