fix disabling of gc by settings gcTime=0 (#463)

samwillis · web-flow · commit 4d2000488b9b · 2025-08-27T15:59:21.000+01:00
diff --git a/.changeset/neat-queens-smile.md b/.changeset/neat-queens-smile.md
@@ -0,0 +1,6 @@
+---
+"@tanstack/electric-db-collection": patch
+"@tanstack/db": patch
+---
+
+fix disabling of gc by setting `gcTime: 0` on the collection options
diff --git a/packages/db/src/collection.ts b/packages/db/src/collection.ts
@@ -746,6 +746,12 @@ export class CollectionImpl<
     }
 
     const gcTime = this.config.gcTime ?? 300000 // 5 minutes default
+
+    // If gcTime is 0, GC is disabled
+    if (gcTime === 0) {
+      return
+    }
+
     this.gcTimeoutId = setTimeout(() => {
       if (this.activeSubscribersCount === 0) {
         this.cleanup()
@@ -784,7 +790,6 @@ export class CollectionImpl<
     this.activeSubscribersCount--
 
     if (this.activeSubscribersCount === 0) {
-      this.activeSubscribersCount = 0
       this.startGCTimer()
     } else if (this.activeSubscribersCount < 0) {
       throw new NegativeActiveSubscribersError()
diff --git a/packages/db/tests/collection-lifecycle.test.ts b/packages/db/tests/collection-lifecycle.test.ts
@@ -239,6 +239,30 @@ describe(`Collection Lifecycle Management`, () => {
       unsubscribe3()
       expect((collection as any).activeSubscribersCount).toBe(0)
     })
+
+    it(`should handle rapid subscribe/unsubscribe correctly`, () => {
+      const collection = createCollection<{ id: string; name: string }>({
+        id: `rapid-sub-test`,
+        getKey: (item) => item.id,
+        gcTime: 1000, // Short GC time for testing
+        sync: {
+          sync: () => {},
+        },
+      })
+
+      // Subscribe and immediately unsubscribe multiple times
+      for (let i = 0; i < 5; i++) {
+        const unsubscribe = collection.subscribeChanges(() => {})
+        expect((collection as any).activeSubscribersCount).toBe(1)
+        unsubscribe()
+        expect((collection as any).activeSubscribersCount).toBe(0)
+
+        // Should start GC timer each time
+        expect(mockSetTimeout).toHaveBeenCalledWith(expect.any(Function), 1000)
+      }
+
+      expect(mockSetTimeout).toHaveBeenCalledTimes(5)
+    })
   })
 
   describe(`Garbage Collection`, () => {
@@ -325,6 +349,24 @@ describe(`Collection Lifecycle Management`, () => {
       // Should use default 5 minutes (300000ms)
       expect(mockSetTimeout).toHaveBeenCalledWith(expect.any(Function), 300000)
     })
+
+    it(`should disable GC when gcTime is 0`, () => {
+      const collection = createCollection<{ id: string; name: string }>({
+        id: `disabled-gc-test`,
+        getKey: (item) => item.id,
+        gcTime: 0, // Disabled GC
+        sync: {
+          sync: () => {},
+        },
+      })
+
+      const unsubscribe = collection.subscribeChanges(() => {})
+      unsubscribe()
+
+      // Should not start any timer when GC is disabled
+      expect(mockSetTimeout).not.toHaveBeenCalled()
+      expect(collection.status).not.toBe(`cleaned-up`)
+    })
   })
 
   describe(`Manual Preload and Cleanup`, () => {
diff --git a/packages/electric-db-collection/tests/electric.test.ts b/packages/electric-db-collection/tests/electric.test.ts
@@ -1030,5 +1030,105 @@ describe(`Electric Integration`, () => {
       await expect(testCollection.utils.awaitTxId(300)).resolves.toBe(true)
       await expect(testCollection.utils.awaitTxId(400)).resolves.toBe(true)
     })
+
+    it(`should resync after garbage collection and new subscription`, () => {
+      // Use fake timers for this test
+      vi.useFakeTimers()
+
+      const config = {
+        id: `gc-resync-test`,
+        shapeOptions: {
+          url: `http://test-url`,
+          params: {
+            table: `test_table`,
+          },
+        },
+        getKey: (item: Row) => item.id as number,
+        startSync: true,
+        gcTime: 100, // Short GC time for testing
+      }
+
+      const testCollection = createCollection(electricCollectionOptions(config))
+
+      // Populate collection with initial data
+      subscriber([
+        {
+          key: `1`,
+          value: { id: 1, name: `Initial User` },
+          headers: { operation: `insert` },
+        },
+        {
+          key: `2`,
+          value: { id: 2, name: `Another User` },
+          headers: { operation: `insert` },
+        },
+        {
+          headers: { control: `up-to-date` },
+        },
+      ])
+
+      // Verify initial data is present
+      expect(testCollection.has(1)).toBe(true)
+      expect(testCollection.has(2)).toBe(true)
+      expect(testCollection.size).toBe(2)
+
+      // Subscribe and then unsubscribe to trigger GC timer
+      const unsubscribe = testCollection.subscribeChanges(() => {})
+      unsubscribe()
+
+      // Collection should still be ready before GC timer fires
+      expect(testCollection.status).toBe(`ready`)
+      expect(testCollection.size).toBe(2)
+
+      // Fast-forward time to trigger GC (past the 100ms gcTime)
+      vi.advanceTimersByTime(150)
+
+      // Collection should be cleaned up
+      expect(testCollection.status).toBe(`cleaned-up`)
+      expect(testCollection.size).toBe(0)
+
+      // Reset mock call count for new subscription
+      const initialMockCallCount = mockSubscribe.mock.calls.length
+
+      // Subscribe again - this should restart the sync
+      const newUnsubscribe = testCollection.subscribeChanges(() => {})
+
+      // Should have created a new stream
+      expect(mockSubscribe.mock.calls.length).toBe(initialMockCallCount + 1)
+      expect(testCollection.status).toBe(`loading`)
+
+      // Send new data to simulate resync
+      subscriber([
+        {
+          key: `3`,
+          value: { id: 3, name: `Resynced User` },
+          headers: { operation: `insert` },
+        },
+        {
+          key: `1`,
+          value: { id: 1, name: `Updated User` },
+          headers: { operation: `insert` },
+        },
+        {
+          headers: { control: `up-to-date` },
+        },
+      ])
+
+      // Verify the collection has resynced with new data
+      expect(testCollection.status).toBe(`ready`)
+      expect(testCollection.has(1)).toBe(true)
+      expect(testCollection.has(3)).toBe(true)
+      expect(testCollection.get(1)).toEqual({ id: 1, name: `Updated User` })
+      expect(testCollection.get(3)).toEqual({ id: 3, name: `Resynced User` })
+      expect(testCollection.size).toBe(2)
+
+      // Old data should not be present (collection was cleaned)
+      expect(testCollection.has(2)).toBe(false)
+
+      newUnsubscribe()
+
+      // Restore real timers
+      vi.useRealTimers()
+    })
   })
 })
