DataMgr 2.2 Compatibility for Custom Relations

(What is DataMgr?)

I have tried to ensure that each version of DataMgr is completely backward compatible with every previous version of DataMgr. With version 2.2, however, I did introduce a small compatibility issue that may require a change in code.

The 2.2 code will work on previous versions, but code written for previous versions may need a small adjustment for new versions.

The reason for this is that while relation fields can call other relation fields, sometimes the combination doesn't make sense. For example, it does make sense to have a "label" relation that gets the value of a "sum" relation for another table. It doesn't make sense, however, to do a sum on a "concat" field (or any normal field that isn't numeric). It also isn't possible for any relation field to get the value from a "list" relation.

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