Collections and Variables

In Power Apps you can use data sources directly or you could use collections or you could use variables. But what is the difference?

Performance and behaviour

In my example app I’m reading data from a SharePoint list and display this in three galleries. Within the app startup I’m setting a variable and a collection to the content presented by the connection to my SharePoint list.

The variable and the collection are set using the following two lines of code in my app on start code. The first line is creating a variable using the Set Function and the second line is creating a collection using ClearCollect.

Set(varItems, Connectors);
ClearCollect(colItems, Connectors)

Now as my app loads the 3 galleries, we can see a difference quite quickly. When I count the items in the three galleries I’m finding 100 or 500 items. So that means that the connection loads only the first 100 items in my connection.

Scrolling through data from connections

And as we scroll through the data, we will find that the gallery needs to load the next page of data and the item count is increasing by 100 every time I try to read the last items in the gallery.

The galleries that load the data using the collection or the variable however don’t show this behaviour.

So should we always use collections/variables?

In the above two short videos you can already see that the collections/variable based galleries took a lot longer to load, while the gallery that used the connection directly performed a lot better straight away.

But there are a few more differences.

Collections and variables and CountRows

Before the data has been loaded, the variable behaves in a different way from the collection and the datasource.

You might have noticed earlier that the variable returns 0 on an empty table, while the other two options return a blank value.

Comparing collections, table variables and data sources in Power Apps Microsoft Power Apps image 16

The variable of the type table, has been initialized as a table, while the collection has not been initialized until the data has been read.

Collections Overview

Then the final major difference between variables and collections is the way Power Apps is managing them within the UI. If we first look at the collection overview, we can see that the data in the collection is being displayed.

Collections overview

When we compare the collections overview with the variables overview then we can see where the variable is defined (in our case in the App.Onstart) and where it has been used. While we can still see the data in the variable as well.

variables overview

The above variables overview could sometimes help when you try to debug you app.

Avatar for Pieter Veenstra

By Pieter Veenstra

Business Applications and Office Apps & Services Microsoft MVP working as a Microsoft Productivity Principal Consultant at HybrIT Services. You can contact me using contact@veenstra.me.uk.

6 thoughts on “Comparing collections, table variables and data sources in Power Apps”
      1. I am trying to build canvas app control for Quotes which I can embed on form for the subgrid(lines). There are items in item table but for the account on quote we have contract which contains set of items not complete and each based on the price list. If the price list match then only pull those items and show in Grid(another) for adding in the grid.

        Quote -> Account(lookup)–>Contract(N)–> Contract Items–> Item –> Price List(N)

        so Ideally I am looking for a way to grab all items with associated pricelist on Quote that fulfills Account contract as well. I know we have done it via JS but trying my hands on canvas app to see if this is possible.

        Thanks

  1. I just came across this and wanted to see if anyone has seen behavior I’ve been noticing:
    1) On screen load, OnVisible has:

    Set(varTempT1,
    Table(
    {
    A:”Row1″,B:1,C:1
    },
    {
    A:”Row2″,B:2,C:2
    },
    {
    A:”Row3″,B:3,C:3
    }

    )
    )

    2) On the screen that loads has a button with OnSelect code as:

    ForAll(Sequence(CountRows(varTempT1)),
    UpdateIf(varTempT1 As K,K.B=Value,{C:Mod(K.C,CountRows(varTempT1))+1})
    );
    Set(varTempT6,varTempT1);
    Set(varTempT3,LookUp(varTempT1,C=1).A);
    Set(varTempT4,varTempT1);
    Set(varTempT5,varTempT1)
    //;RemoveIf(varTempT1 As K,true);
    //;Set(varTempT1,varTempT4)

    3) On the screen, there are few labels and data table to observe the variables:

    Label1 has Text: LookUp(varTempT1,C=1).A
    Label2 has Text: With({T:LookUp(varTempT1,C=1).A},T)
    Label3 has Text: LookUp(Table({T1:varTempT3}),1=1).T1
    DataTable1 has Items: varTempT1
    DataTable2 has Items: varTempT4

    On click of the button, Label1, Label2 and DataTable1 never show updated value on screen, while Label3 and DataTable 2 do, why so?
    By uncommenting the last two line in the button code, and restarting the app and loading the screen:
    – varTempT1 is populated, other variables are empty
    And on one click of the button:
    – varTempT1 and all other variables (varTempT4, varTempT5 and varTempT6) become empty, It’d be expected that no variables would be empty
    – if RemoveIf(varTempT1 As K,true); is replaced with Set(varTempT1,Table()) or Set(varTempT1,Blank()), and the last line (Set(varTempT1,varTempT4)) is commented out, the variable varTempT1 doesn’t become empty nor does code show any error

    Is there something I’m doing wrong, or Power Apps not working, or I shouldn’t be using variables as Table type and instead use collections?

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