Too many watchers affecting performance

What Are Watchers in PowerApps?

In PowerApps, a “watcher” refers to an element that continuously observes changes in the app, such as:

1. OnChange Events: Monitors changes in input fields.
2. OnVisible and OnStart: Triggers when a screen is loaded or an app starts.
3. Formulas Evaluating Frequently: Functions like Filter(), LookUp(), or Sort() running too often.
4. Collections and Variables Changing Dynamically: Updating large datasets repeatedly can cause performance lags.
5. Timers, Data Refreshes, and Real-time Triggers: When too many timers or Refresh() functions are active.

When the number of watchers grows excessively, PowerApps has to constantly track multiple events, leading to slower performance and app crashes.

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Step-by-Step Guide to Optimizing Watchers in PowerApps

Step 1: Identify Performance Bottlenecks

1. Enable Debugging Mode: Use Monitor Tool in PowerApps to track execution logs and see which functions are running excessively.
2. Check Network Calls: Open Developer Tools (F12) in your browser, go to the Network tab, and check how many requests PowerApps is making.
3. Use Performance Profiler: PowerApps offers a built-in performance profiler to analyze response times for different elements.

Step 2: Reduce Unnecessary Watchers

1. Avoid Too Many OnChange Events

Problem: When a TextInput, Dropdown, or ComboBox has an OnChange event, PowerApps continuously monitors it.

Solution:

• Instead of triggering an action for every keystroke, use a button click to apply changes.
• Example: Instead of this:
  TextInput1.OnChange = Set(varSearch, TextInput1.Text) Use this approach:
  Button1.OnSelect = Set(varSearch, TextInput1.Text) This ensures updates happen only when needed, not for every character typed.

2. Reduce Unnecessary Timer Controls

Problem: PowerApps timers continuously track time and execute actions, consuming resources.

Solution:

• Disable timers unless they are absolutely necessary.
• Example: If a timer is used to refresh data every 5 seconds, replace it with a manual refresh button.

3. Optimize LookUp and Filter Functions

Problem: Too many LookUp(), Filter(), or Search() functions in a gallery or screen force PowerApps to constantly evaluate data.

Solution:

• Store filtered results in collections or variables to reduce repeated computations.
• Example: Instead of:
  Gallery1.Items = Filter(Orders, Status = "Pending") Use:
  ClearCollect(CollectedOrders, Filter(Orders, Status = "Pending")); Gallery1.Items = CollectedOrders This ensures filtering only happens once, not every time the gallery refreshes.

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Step 3: Optimize Data Sources and Queries

1. Reduce Data Calls Using Delegation

Problem: Fetching too much data slows down performance.

Solution:

• Use delegation-friendly queries that fetch data efficiently.
• Example: Instead of Filter(MyList, Title = "ABC"), use indexed columns in SharePoint or Dataverse.
• Use delegable functions like StartsWith() instead of Search().

2. Avoid Repetitive Data Refresh Calls

Problem: Using Refresh() frequently forces PowerApps to reload all data, leading to performance issues.

Solution:

• Refresh data only when necessary, such as after form submission.
• Example: Instead of refreshing the whole dataset:
  Refresh(MyDataSource) Refresh only the needed record: PowerAppsCopyEditLookUp(MyDataSource, ID = SelectedRecord.ID)

3. Reduce Items in Galleries and Data Tables

Problem: If a gallery loads 1000+ items, it significantly slows down PowerApps.

Solution:

• Use pagination (e.g., load only 50 records at a time).
• Use Lazy Loading by showing a limited number of records initially and loading more when needed.

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Step 4: Optimize Variables and Collections

1. Reduce Excessive Variable Updates

Problem: Setting variables too frequently increases processing load.

Solution:

• Use Set() and UpdateContext() only when required, not inside repetitive loops.
• Example: Instead of
  ForAll(MyCollection, Set(varTotal, varTotal + Value(ThisRecord.Amount))) Use PowerAppsCopyEditSet(varTotal, Sum(MyCollection, Amount)) This prevents the app from tracking multiple variable updates.

2. Clear Unused Collections and Variables

Problem: PowerApps keeps unused collections in memory, affecting performance.

Solution:

• Use ClearCollect() instead of Collect() to avoid unnecessary accumulation.
• Use Clear() to remove unused data from memory.

Example:

Clear(MyCollection);
ClearCollect(MyCollection, Filter(DataSource, Status = "Active"))

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Step 5: Optimize Screen and Component Loading

1. Load Data Only When Needed

Problem: If all data loads at app startup, the app slows down.

Solution:

• Load only essential data on app launch (OnStart event).
• Load additional data on demand when a user navigates to a screen.

Example: Instead of loading everything on App.OnStart, load data only when needed:

Screen1.OnVisible = ClearCollect(ActiveUsers, Filter(Users, Status="Active"))

2. Use Components Instead of Duplicating Controls

Problem: Duplicating the same UI elements on multiple screens increases app complexity.

Solution:

• Use Reusable Components instead of creating multiple copies of the same control.
• This reduces watchers since PowerApps tracks one component instead of multiple controls.