[CAY-2468] Support subqueries in Expression API

• Type: Task
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 4.2.M1
• Component/s: Core Library, Database integration
• Assignee: Nikita Timofeev
• Reporter: Nikita Timofeev
• Created: 29/Aug/18 09:40
• Updated: 09/Jan/19 12:14
• Resolved: 09/Jan/19 12:14

Description

Currently there is no way to use subqueries in SelectQuery or ObjectSelect.
So we need a way to do so in Expression API.

Simple version can be implemented like this:

ObjectSelect<Painting> subquery = ObjectSelect.query(...);
long count = ObjectSelect.query(Artist.class)
        .where(ExpressionFactory.exists(subquery))
        .selectCount(context);

Also we need a way to use expressions from top level query in a subquery. Maybe it can be new expression (like Artist.ARTIST_NAME.enclosing())

In a first iteration this should support EXISTS and IN subqueries.

Issue Links

• requires: CAY-2465 New SelectTranslator implementation