Improve FDBIndex.count and FDBObjectStore.count performance

src/FDBIndex.ts

@@ -247,14 +247,7 @@ class FDBIndex {
 
         return this.objectStore.transaction._execRequestAsync({
             operation: () => {
-                let count = 0;
-
-                const cursor = new FDBCursor(this, key);
-                while (cursor._iterate() !== null) {
-                    count += 1;
-                }
-
-                return count;
+                return this._rawIndex.count(key);
             },
             source: this,
         });

src/FDBObjectStore.ts

@@ -549,14 +549,7 @@ class FDBObjectStore {
 
         return this.transaction._execRequestAsync({
             operation: () => {
-                let count = 0;
-
-                const cursor = new FDBCursor(this, key);
-                while (cursor._iterate() !== null) {
-                    count += 1;
-                }
-
-                return count;
+                return this._rawObjectStore.count(key);
             },
             source: this,
         });

src/lib/Index.ts

@@ -25,7 +25,7 @@ class Index {
         name: string,
         keyPath: KeyPath,
         multiEntry: boolean,
-        unique: boolean
+        unique: boolean,
     ) {
         this.rawObjectStore = rawObjectStore;
 
@@ -176,6 +176,17 @@ class Index {
             source: null,
         });
     }
+
+    public count(range: FDBKeyRange) {
+        let count = 0;
+
+        // eslint-disable-next-line @typescript-eslint/no-unused-vars
+        for (const record of this.records.values(range)) {
+            count += 1;
+        }
+
+        return count;
+    }
 }
 
 export default Index;

src/lib/ObjectStore.ts

@@ -207,6 +207,17 @@ class ObjectStore {
             rawIndex.records.clear();
         }
     }
+
+    public count(range: FDBKeyRange) {
+        let count = 0;
+
+        // eslint-disable-next-line @typescript-eslint/no-unused-vars
+        for (const record of this.records.values(range)) {
+            count += 1;
+        }
+
+        return count;
+    }
 }
 
 export default ObjectStore;

src/test/fakeIndexedDB/fakeIndexedDB.ts

@@ -831,4 +831,33 @@ describe("fakeIndexedDB Tests", () => {
         const dataView2 = new DataView(key);
         assert.equal(dataView2.getUint32(0), 1234567890);
     });
+
+    it("FDBObjectStore.count performance should be reasonable (issue #94)", (done) => {
+        const N = 10000;
+        const openreq = fakeIndexedDB.open("test94");
+        openreq.onupgradeneeded = (event) => {
+            const db = event.target.result;
+            const store = db.createObjectStore("items", {
+                keyPath: "key",
+                autoIncrement: true,
+            });
+            for (let i = 0; i < N; i++) {
+                store.put({ i });
+            }
+        };
+        openreq.onsuccess = (event) => {
+            const db = event.target.result;
+            const request = db
+                .transaction("items")
+                .objectStore("items")
+                .count();
+            request.onsuccess = (event2: any) => {
+                assert.equal(event2.target.result, N);
+                done();
+            };
+            request.onerror = (event2: any) => {
+                done(event2.target.error);
+            };
+        };
+    });
 });