Handling delegation warnings

[morall]

I have a Gallery that is using this as a filter:

Sort(
    If(
        'Already Viewed Toggle'.Value=true, 
        Filter(
            'Pipeline Candidates',
            'iCIMS ID' in Filter('Morgan Audit Logs', 'viewed by'=User().Email, 'Created On' < DateAdd(Now(), 1, Minutes)).'icims id'
        ),
        'Pipeline Candidates'
    ),
    'Created On',
    Descending
)

I am trying to break this out to avoid delegation warnings. When the App loads, i want to set a variable

Set(sorted_list, Filter('Morgan Audit Logs', 'viewed by' = User().Email).'icims id')

And then change the Gallery items filter:

Sort(
    If(
        'Already Viewed Toggle'.Value=true, 
        'Pipeline Candidates'.'iCIMS ID' in sorted_list,
        'Pipeline Candidates'
    ),
    'Created On',
    Descending
)

I'm getting an error for the if statement. What am I doing wrong? 

[mdevaney]

@morall 
The IF statement is not a delegation friendly function.  You must move it to the outer scope of the formula to remove the warning due to IF.

If(
    Sort(
        'Already Viewed Toggle'.Value=true, 
        Filter(
            'Pipeline Candidates',
            'iCIMS ID' in Filter('Morgan Audit Logs', 'viewed by'=User().Email, 'Created On' < DateAdd(Now(), 1, Minutes)).'icims id'
        ),
        'Created On',
        Descending
    ),
    Sort(
        'Pipeline Candidates'
        'Created On',
        Descending
    )
)

However, other functions within your formula cannot be delegated like IN, NOW and USER().EMAIL.

NOW and USER().EMAIL can be resolved by storing it in a variable upon the screen becoming Visible.  The IN function does not have any known workaround though.

---
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[RandyHayes · Accepted solution]

@morall 

You're not going to be able to escape the delegation issue with this approach.  

You will still need to do a Filter on your Gallery as you had in the first formula.  The only thing you are replacing is the internal iCIMS ID Filter.

But, if I understand your scenario, you still want to have the records that are in the Pipeline Candidates with iCIMS ID's that are in the sorted_list.

This is a scenario where it would be best to pull the Pipeline Candidates into a collection and then use your filter on that.  It would then not give you delegation warnings.

Somewhere in your app (like OnStart, OnVisible, or on some other control) add a ClearCollect(colPipelineCandidates, 'Pipeline Candidates') or, preferably with some initial filter to limit the items.

Then follow what you have in your first formula except substitute the 'Pipeline Candidates' with the colPipelineCandidates.

I hope this is helpful for you.

[RandyHayes]

@morall yes, I forgot to mention in my post, the reason you are not going to escape the delegation is the IN operator as was more clearly stated by @mdevaney 

Looks like we posted at the same time.

[mdevaney]

@RandyHayes 

Not to worry.  I enjoyed reading your thoughts on the subject 🙂

---
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[RandyHayes]

@mdevaney 

Thanks 😁  I started going down that road in my third paragraph but my mind slipped and I forgot to complete the thought. 

<pointing to head> Sometimes the hamster falls asleep in the wheel! 🤔

[morall]

Hey Randy,

This is great. Question about using OnStart. 

Can I load all of my data into objects like: 

set(var1, DataSource1)

set(var2, DataSource2)

Is there a limit to how much I can "load upfront"? If there isn't, this solves pretty much all of my problems with performance.

[Pstork1]

The only limit is the amount of storage space on your device.  But I wouldn't say it solves your performance problem.  It just puts all your performance issues at the point where the app loads.  Taking 5 minutes to load an app so you can cache all the data locally may not be considered a solution to your performance problems.

[morall]

Is there a way to limit the number of records fetched from a data source?

the data source im pulling from has 1,000's of records, but I only really need the most recent 100. 

[RandyHayes]

@morall 

Agree with @Pstork1 , if performance is an issue, then loading large amounts up front will give you a hard performance hit to start.  After that, your performance should be quite fine, but as mentioned, if the user is waiting 5 minutes for the OnStart to do its thing, they might not like it.

How we've handled that in the past is to not do things in OnStart that are Data bound.  We put them separate in the App (usually on a Toggle control) and then "fire" them as needed.  So, we kind of stagger the performance hits.  Its not perfect, but I have yet to see any app that can not take a performance hit when bringing down large amounts of data.  The trick in our case was to have the first screen show fast (User thinks all is well and is happy), then get primary data needed - again doing this through a Toggle control so that the user can still do other things that are not data specific (usually not much, but they at least think things are working).  Then when we have data downloaded, we enable data specific controls.  It's a balance of logic design and interface design to pull it off in an effective way.

To add to the above (may not apply in your case, but may be an interesting read for some) - if they are on Mobile devices, we then SaveData and detect that next time they come in so they don't have to wait.  However, getting that data updated on the device is a series of "how does it need to be updated?" questions. 

1) All updated regardless? We just refresh and take the performance hit again 

2) All updated if changed?  We use a separate list or other indicator to "version" the main list (ex. we sometimes use a SharePoint list with a series of records.  The first column is the name of the SharePoint list it refers to, the second column is the "version" which is the date at which the last change was made.  We use flow on the main lists to keep that updated when changes are made.

3) Only update what is changed? This is a challenging one and very specific to the application. Not to go too deep into it, but the concept is - if a user uses a certain record (i.e. selects it) we then go get THAT record and update it in the stored data.  There are a lot of gotchas in this method, but it works in some scenarios.

EDIT: Forgot to mention...always make use of the Concurrent function when possible for multiple data sources.