How do I write an Expression that will filter an Entity with an empty to-many relationship?

Question

I have the following structure:

Invoice <->> LineItem

How do I write an Expression that will query the database for all the Invoice objects that do not have any related LineItem objects?

There is no Invoice.LINE_ITEMS.isEmpty() and Invoice.LINE_ITEMS.isNull() will not work because myInvoice.getlineItems() will return an empty collection not null.

score 2 · Answer 1 · answered Apr 14 '17 at 11:59

2

If you do an outer join using the null check should work. Write your expression like this:

Invoice.LINE_ITEMS.outer().isNull()

answered Apr 14 '17 at 11:59

Hugi

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Not exactly intuitive, but does seem to work. I feel a pull request coming on. – David Avendasora Apr 23 '17 at 13:32
Also, does not appear to work in-memory. Only when querying the database. – David Avendasora May 04 '17 at 22:13

How do I write an Expression that will filter an Entity with an empty to-many relationship?

1 Answers1