search: swich Set.contains to index-based lookup. (#8391)

Author: isoos

app/lib/search/mem_index.dart

@@ -72,7 +72,7 @@ class InMemoryPackageIndex {
       if (apiDocPages != null) {
         for (final page in apiDocPages) {
           if (page.symbols != null && page.symbols!.isNotEmpty) {
-            apiDocPageKeys.add(IndexedApiDocPage(i, doc.package, page));
+            apiDocPageKeys.add(IndexedApiDocPage(i, page));
             apiDocPageValues.add(page.symbols!.join(' '));
           }
         }
@@ -376,7 +376,8 @@ class InMemoryPackageIndex {
       // are multiplied. We can use a package filter that is applied after each
       // word to reduce the scope of the later words based on the previous results.
       /// However, API docs search should be filtered on the original list.
-      final packages = packageScores.toKeySet();
+      final indexedPositiveList = packageScores.toIndexedPositiveList();
+
       for (final word in words) {
         if (includeNameMatches && _documentsByName.containsKey(word)) {
           nameMatches ??= <String>{};
@@ -406,7 +407,7 @@ class InMemoryPackageIndex {
             if (value < 0.01) continue;
 
             final doc = symbolPages.keys[i];
-            if (!packages.contains(doc.package)) continue;
+            if (!indexedPositiveList[doc.index]) continue;
 
             // skip if the previously found pages are better than the current one
             final pages =
@@ -660,8 +661,7 @@ class IndexedPackageHit {
 
 class IndexedApiDocPage {
   final int index;
-  final String package;
   final ApiDocPage page;
 
-  IndexedApiDocPage(this.index, this.package, this.page);
+  IndexedApiDocPage(this.index, this.page);
 }

app/lib/search/token_index.dart

@@ -250,15 +250,18 @@ class IndexedScore<K> {
     }
   }
 
-  Set<K> toKeySet() {
-    final set = <K>{};
+  /// Returns a list where each index describes whether the position in the
+  /// current [IndexedScore] is positive. The current instance changes are
+  /// not reflected in the returned list, it won't change after it was created.
+  List<bool> toIndexedPositiveList() {
+    final list = List.filled(_values.length, false);
     for (var i = 0; i < _values.length; i++) {
       final v = _values[i];
       if (v > 0.0) {
-        set.add(_keys[i]);
+        list[i] = true;
       }
     }
-    return set;
+    return list;
   }
 
   Map<K, double> top(int count, {double? minValue}) {