Possible bug: Gallery controls not updating properly since latest patch

[Reinholtz]

In earlier versions of the app (3.23052.19) I created a Vertical Gallery populated from a filtered SQL table and with a simple Label control to flag if a value had been changed by the user (in a Text input control in the gallery) in relation to the value in the table. This worked fine, and I could go through the gallery and patch only the records that were flagged as changed.

Now, in version 3.23081.15 I've done the exact same thing, but the label flags ALL records as changed (even though they are not). What is even stranger is, that the erroneous "flag" magically gets reset to the correct value as I manually scroll through the gallery...

[poweractivate]

@Reinholtz 

Check if going to Settings -> Support helps. Then click on Edit near Authoring Version. Then select oldest version then click the Reload + apply version button.

The farthest you may go back for now is 3.23074.17 and it's only temporary. In the future even this version may no longer be possible to go back to as updates continue. Just in case, is the issue still there in that version? It may help to know when it started to appear. If it's still there, it may not be possible to go back further and it means the issue was maybe introduced earlier than 3.23074.17.

In this case you may also want to file support ticket with these steps if you think it is a bug. for further troubleshooting.

[Reinholtz]

@poweractivate 

Unfortunately, the issue must have been introduced (as you suspected) before version 3.23074.17. I reloaded and applied the application with that authoring version, and even created a new gallery with controls to test, but alas... The same thing still happens: the label control (and I've tried with other types of controls as well, as well as just filtering the gallery records with a simple "<>" operation) does not catch that the values are the same until I scroll through the gallery. It is as if it is only the records that are currently visible on screen that updates (as my bug-catcher-"ticker" decreases the count of erroneous flags only for the amount of records currently on screen as I scroll down the gallery).

Hope this helps your detective work. And thank you for real quick feedback!

[poweractivate]

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@Reinholtz wrote:

@poweractivate 

...values are the same until I scroll through the gallery. It is as if it is only the records that are currently visible on screen that updates (as my bug-catcher-"ticker" decreases the count of erroneous flags only for the amount of records currently on screen as I scroll down the gallery)....

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@Reinholtz I am not sure that's new though. When there are a high number of records, the Gallery does not load all records at once. You may check this by having your Gallery point to a Data source that has a lot of records, say, 300 or so. You may place a label and then put for the Text property

 CountRows(Gallery1.AllItems)
//replace Gallery1 above with the actual name of your Gallery Control

To my knowledge, this probably won't return 300, more like 10 or so. I don't think this is new, and I believe it worked like this since the beginning. The behavior where you scroll down and it loads more records only then is a behavior I believe was there from the beginning.

However, you claim it was working before, so maybe there was a change. 

One change may actually be you had far less records in the Gallery before, and now you have more that went over the internal Gallery limit that it loads at once (not sure of the exact number that is).

If so you are noticing behavior that is by design, probably from the very beginning actually, and not a recently introduced change. 

The behavior of only loading the first few records in the Gallery at first, and then loading only in batches gradually as you scroll down is something I believe was there from the very beginning, not a recently introduced change.

In order to accomplish what you are trying to do then you should do it another way not relying on the Gallery Items being a complete set of all the items.

When considering these alternate ways such as Collections, note that all individual function calls are subject to the data row limit (500, which can be raised in the settings up to a max of 2000). For example, even a fully delegable Filter function call can return no more than 2000 filtered records, so if there are more than that, continue to chain && or change the Filter operators to bring it down to below the data row limit. Fully delegable is still better than non-delegable, because non-delegable will only scan literally the first X records that are within the data row limit and skip everything after that. Fully delegable may process up to all records in the data source, but note that even so, only the first X records satisfying the criteria up to the data row limit are returned in one function call, and there's no way to escape this, so make sure (suppose you use a fully delegable Filter function for example), that you don't have more than X records in your data source that actually satisfy the Filter criteria (X being the data row limit, which can be no more than 2000). Another example is a single function call to ClearCollect - it will only do so with at most 2000 records assuming 2000 is the data row limit you have set in your app, and so forth.

There are tricks to go above the data row limit as well through batching, (these rely on the underlying the key fact that it's limited to the data row limit per individual function call), beware of overusing such tricks and be sure to unload the records when done. Keeping a high number of records in memory at once in Power Apps Canvas App can lead to memory issues, slowdowns, etc. - the data row limit is there for a reason, and it's best to avoid such tricks at all if you can and just try and have your Filter fully delegable and with operators and criteria that bring it down to well below the data row limit by structuring it strategically. 

However if you are sure your behavior with the Gallery may be unique to a newer version, you may check if raising the support ticket as above may get you further guidance in case you suspect it's a bug.

See if it helps in case @Reinholtz 

[Reinholtz]

Thank you again, @poweractivate 🙂

I know the limitations of PowerApps not being able to handle large amounts of data, but I'm looking at 90-ish records, so there shouldn't be an issue.

I'll keep on looking to see if there's anything I've done to mess things up 🙂

Thank you for all your help!

[poweractivate]

@Reinholtz You're right, also I did a quick test, and I did not get any issues with Gallery.AllItems at all and I got all the items to load at once even when it was more than 1000 items. However, it's possible I got this only on quick test using collections, and if it were more detailed I would start to see different behavior. I also tested on the current authoring version of Power Apps Canvas App. I suggest you do indeed check and see what may be going wrong in your case @Reinholtz