Spring Boot generates invalid MySQL query (only_full_group_by)

Question

I'm using Spring Boot 1.5.2 and the following @Query:

@Query(value = "SELECT m FROM Message m WHERE m.from.userId = :myId OR m.to.userId = :myId GROUP BY m.from.userId, m.to.userId ORDER BY m.date DESC")
List<Message> chatOverview(@Param("myId") final Long myUserId);

The intention of the query is to create a chat messenger overview, where you see the last message of each conversation you had. It works fine for me in dev, but in production (newer MySQL database version) I get this error:

java.sql.SQLSyntaxErrorException: Expression #1 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'message0_.message_id' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by

I read in this thread what the reason for this change was, however I couldn't find a way to fix this with JPA / Spring. I cannot change any settings in the production MySQL database and I would like to avoid any upgrading in Spring either. How can I fix my query?

Answer 1

Here is the definition and purpose of the GROUP BY (see section 4.7) clause:

The GROUP BY construct enables the aggregation of result values according to a set of properties.

That means it is used only if you're aggregating (sum, avg, max, min, ...) the value(s) of a field(s). But in your case I don't see any aggregation function. So just remove the GROUP BY clause and everything should be fine:

SELECT m FROM Message m WHERE m.from.userId = :myId OR m.to.userId = :myId ORDER BY m.date DESC

Grouping on userId doesn't make sense too because all the entities returned by this query will have the same value for this field.