java - What does MAX aggregation on an entity identification variable do? -


i'm trying migrate old code uses jpa 1.0 , hibernate 3.3 (yes, it's really old) different (non-sql) data api. 1 of queries looks this:

select tx.transactionid, max(tx), sum(tx.amount)   transaction tx   tx.customerid = :customerid   , ... // etc   group tx.transactionid 

my question: what should result of max(tx) be? of documentation i've seen claims max valid comparable scalar values (numbers, strings, dates), not entity references. context, query in fact returns instances of transaction, can't tell instance (specific persisted entities? composite entities of kind?) or how relate grouped result sets.

is hibernate extension spec? couldn't find in hibernate docs either, , wasn't able locate code in hibernate sources deals specific behavior. don't care either way (since have rewrite entire call in different manner anyway), know replacement should do.

anybody recognize this?


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