Smalltalk - Re: Need help understanding "Inconsistent Values in row"

Re: Need help understanding "Inconsistent Values in row"

Posted by Alan Knight on Oct 22, 2020; 2:16pm
URL: https://forum.world.st/Need-help-understanding-Inconsistent-Values-in-row-tp5123817p5123820.html

The "an Object" value in a row indicates that nothing has written a value there yet. Because nil is a valid value, we need a placeholder to indicate the absence of a value, so there's a unique (Object new) that goes there.

One debugging tool is the debugWrite attribute on a mapping. That normally does a halt, but could be modified for production to log instead. The tricky part with that is that when there's a conflict, what you often want to know is who wrote the previous value. However, in your case it seems easier, because this just seems wrong. Basically, it seems to me that this is likely to be identity/caching, a lookup problem, or a race condition. With normal logic it should never be overwriting a primary key field. Does this always happen on the id field? Of the same table?

I think what I would try is instrumenting that method. In particular, check if row has an id which is different than the target. I can't see how that would ever be valid, and see if there's additional information you could provide, e.g. print that rowmap's keys and values, or at least the keys that are the two in question and the values, if present. You could also try to put some validation logic into the logic that adds to the rowmap, where if it ever adds something but then the lookup produces a different result you could log that or cause an error.

The other thing that seems suspicious to me is if this might be inheritance-related. I notice the table name is KPELEMENT, which seems more general than an account. Maybe there's something to do with the inheritance mappings/lookup that's confusing it. If this problem is on different tables, are they always inherited?

On Thu, Oct 22, 2020 at 9:33 AM jtuchel <[hidden email]> wrote:

Joachim Tuchel
15:31 (jetzt)
an VA Smalltalk

I have a problem popping up in production much more often than I'd like. Unfortunately, I cannot reproduce it in any of our test environments. Users told me what they are doing, and I tried the same dozens and hundreds of times, but I don't understand what is going on.

When users commit a Transaction after some operation, they sometimes get an "Inconsistent values in field" error. Sometimes they also get a "Conflicting Values in Rows", which seems to be somewhat the same thing...?).

A few things are strange here. But let's first look at a part of the walkback:

DirectMapping>>#mapFromObject:toTarget:puttingRowsIn:
receiver = a DirectMapping(id) arg1 = a Konto (1572965): 1791 Umsatzsteuer frühere Jahre
arg2 = a Konto (1572965): 1791 Umsatzsteuer frühere Jahre
arg3 = a RowMapForMementos
temp1 = 1572965
temp2 = 1572965
temp3 = a DatabaseRow(KPELEMENT)
Field(KPELEMENT.id)->1572848
Field(KPELEMENT.version)->an Object Field(KPELEMENT.typ)->'KO' Field(KPELEMENT.bezeichnung)->an Object Field(KPELEMENT.kontonummer)->an Object Field(KPELEMENT.anfangssaldo)->an Object Field(KPELEMENT.abschlusssaldo)->an Object Field(KPELEMENT.euerKz)->an Object Field(KPELEMENT.cont_id)->an Object Field(KPELEMENT.rahmen_element_id)->an Object Field(KPELEMENT.wurzel_id)->an Object Field(KPELEMENT.metakonto_nr)->an Object Field(KPELEMENT.kto_orig_id)->an Object

So first thing here is: it seems most contents of the Row are "an Object" which definitely is rubbish.
But reading the code of this method and looking at the temps and args, I have at least some idea of what might be going wrong here. This is the method:

mapFromObject: anObject toTarget: target puttingRowsIn: aRowMap

   | dbValue value row |

   self canWrite ifFalse: [^self].
   value := self getValueFrom: anObject.
   value := self session realObjectFor: value ifNone: [^self].
   dbValue := self convertedDbValueOf: value.
   row := aRowMap findOrAddRowForTable: self field table withKey: target.
   row at: field put: dbValue

What I find interesting is that the row which is displayed here is not the one that the meapper was looking for. The row to be changed has the id 157296, but the row in the Walkback has the id Field(KPELEMENT.id)->157284. So I guess the problem is that #findOrAddRowForTable: self field table withKey: target. returns the wrong row...

There is no point in changing the contents of ID anyways, since it is the primary key of the row....

So what would a Glorp pro do to "debug" this deeper - especially given that we have no way to reproduce this problem (yet)?

Joachim

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