Possible bug with Query Tags and implicit .value in Ignition 8.3.1

Ignition
1

Hello,

I might be encountering a bug with Query Tags in Ignition 8.3.1.

In our projects, we use UDTs across multiple plants, and inside these UDTs we have several simple Query Tags that read configuration parameters stored in a database.

This approach works correctly on most of our plants and most UDT instances. However, in some rare cases (like the example below), the Query Tag returns null, even though the query should return a valid value.

For example, here I am simply reading a parameter for a specific LineID:

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image1958×986 130 KB

As shown in the screenshot, the Query Tag returns null, but if I execute the exact same query directly in the database, it correctly returns the expected value.

After investigating, I found that if I modify the query to explicitly reference the tag value ({…LineID.value} and not {…LineID}):

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image1935×659 96.2 KB

then the Query Tag immediately returns the correct result.

For now I will probably add .value everywhere to avoid the issue, but I find this behavior surprising because:

  • This happens only on a few UDT instances out of ~30

  • Other instances using the exact same query work correctly

  • It appears on one gateway running 8.3.1

  • The lineID tag itself has Good quality and the correct value

My understanding was that when referencing a tag without specifying a property, Ignition implicitly uses .value, so both syntaxes should behave the same.

So my question is:

  • Is this a known issue or regression in 8.3.x?

  • Or is it considered best practice to explicitly use .value in Query Tags?

Thanks!

2

Have you tried putting the refrence in quotes? "{…LineID}"

3

Yes, I tested it just in case, but the tag returns an error with the quotes. LineID is an int.

4

I don't see anything that exactly lines up with this, but I would encourage updating to 8.3.4 once it's available (should be as soon as this week) it's now available.

If you're still having issues after that, I'd say to contact support. Your expectation that .value should work (and consistently) is totally valid.

5

Thanks for the answer. We will install the new version and test.

However, I would like to add another feedback. Today I encountered a similar issue on another one of our gateways running 8.3.3.

In a Perspective page, I have several custom properties. One of them constantly returns 0, but only for one specific UDT instance.

This happens whether the property is bound through an expression binding:

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image1153×1219 122 KB

or through a direct tag binding:

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image1200×1173 121 KB

As shown in the screenshots, the displayed result is always 0, while the actual tag value is 10.

Again, the only way to get the correct value is to explicitly reference .value. Once .value is added, the correct value is returned.

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image1042×509 30 KB

Adding .value itself is not a problem. The main issue is that it would require us to modify all of our Ignition projects for this newer version. At first glance everything seems to work correctly, but in some specific UDT instances this bug appears, which ends up creating unexpected and confusing behaviors for users in the application.

So it is difficult for us to reliably detect where this issue might occur, but as soon as I click on “Restart tags” in the designer in the folder that is causing the problem, the error disappears.

6

I'd definitely contact support at this point.

It seems like there might be something going on within the tag execution system that's manifesting as these symptoms in two different areas.