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robin.bygrave
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@Formula2 is a logical-path alternative to @Formula and a full replacement for it.
Where @Formula requires physical SQL (${ta} placeholders and hand-written joins),
@Formula2 takes a property-path expression and resolves the required joins
automatically:
@Formula2("coalesce(familyName, parent.familyName)")
String derivedFamilyName;
The path prefixes (parent, parent.parent, ...) define the joins needed to
satisfy the formula. Supported everywhere @Formula is:
- select() — root and nested-fetch paths, auto-joined
- where() — predicate paths trigger the extra joins
- orderBy() — order-by paths trigger the extra joins
- having()
- DDL — excluded from generated columns (read-only, like @Formula)
Default behaviour matches @Formula: included in the default select unless marked
@Transient, in which case it is opt-in but still auto-joins when selected.
Implementation:
- Parse @Formula2 after associations are wired, into a logical select fragment
plus the set of join paths (BeanDescriptor/BeanProperty).
- DeployPropertyParser registers formula2 join paths into query includes so the
existing predicate-include -> extra-join machinery builds the LEFT JOINs.
- ElPropertyChain prefixes all ${}/${path} placeholders for nested-path use.
- SqlTreeBuilder accumulates formula2 joins for select paths.