Strange behavior from inMemory tables when grouping

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Posted on by BrandonSA

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Hi everyone

I just learnt about some strange behaviour from AX that occurs when you group on inMemory tables.

If I say

MyTable t;

select ColA from t group by ColA;
print t.ColB;

then naturally, ColB is null if MyTable is a regular or tempDB table because it isn't part of the field list, nor is it being grouped on which means it's truncated, but strangely, ColB has a value if MyTable is inMemory.
I know these table types are stored differently between the AOS and SQL depending on what type they are, but is this behaviour a bug or a feature?
If it's a feature, what are the rules for what value ColB gets and is there any documentation for it? Does ColB just get the first value for each group of ColA?

Any thoughts appreciated. Tx

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Martin Dráb 237,987 Most Valuable Professional on at

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I've never seen such a problem with InMemory tables.

Your code snippet seems to print ColB variable, not t.ColB field. Is your actual code correct? Can you please give us an example that we could run, using a standard temporary table? For example, you could use TmpSearchResult table, if it exists in AX 2012 (I can't be sure because I'm on F&O).

What value do you see in the field?

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BrandonSA 1,673 on at

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Hi Martin

Thank you for the reply. I did have a typo in my post, omitting t when printing ColB - I've updated my post to correct it.

I just set the scenario up in Ax and ran it. Here is the result: (MyTable is inMemory)

Ax Version is Ax 2012 R2 CU7

PS. Interestingly, I just ran the same job in F&O (10.0.33) and still get the same behavior:

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Martin Dráb 237,987 Most Valuable Professional on at

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Interesting. I'm not sure if I can find much about how the kernel handles it, but I'll try. Could you please share your code, so everyone doesn't have to type it again?

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BrandonSA 1,673 on at

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Sure. Thank you Martin

static client void Job49(Args _args)
{
MyTable t;

void insert(str a, str b)
{
t.initValue();
t.ColA = a;
t.ColB = b;
t.insert();
}

insert('Alpha', 'One');
insert('Gamma', 'Two');
insert('Alpha', 'Three');
insert('Beta', 'Four');

while select ColA from t group by ColA
{
info(strFmt('%1 %2', t.ColA, t.ColB));
}
}

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Martin Dráb 237,987 Most Valuable Professional on at

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All I can say is that I see the same behavior as you. It looks wrong to me and I have no explanation for it.

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BrandonSA 1,673 on at

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Thanks Martin for looking into it, it is a very strange error

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