jwgmeligmeyling / blaze-persistence-querydsl Goto Github PK

Left nested sets can be used for the following two purposes:

• Specifying an order by and/or limit clause on a set operation sub result
• Overriding default precedence (INTERSECT (ALL) takes precedence over UNION/EXCEPT (ALL) according to ANSI SQL).

Left nested sets are not considered in #8. There's a few things to address in order to resolve this:

• Currently we render against a CriteriaBuilder. In order to support a left nested set in the root, we have to render against a CriteriaBuilderFactory in order to be able to use CriteriaBuilderFactory#startSet.
• That said, we also need an equivalent for CriteriaBuilderFactory in the QueryDSL integration for consistency
• Because BlazeJPAQuery and SetOperation are derived from QueryDSL's ProjectableSQLQuery and UnionOperation respectively, which do not support left nested sets, the underlying expression model has to change to store the nesting information.

• Move BlazeCriteriaVisitor and BlazeJPAQuery to impl package.
• Rewrite tests to use the fluent builder API.
• Add service provider API
• Remove compile time dependency on implementation

For example:

String queryString = new BlazeJPAQuery<TestEntity>(entityManager, cbf)
    .select(book).from(book).where(book.id.lt(1337L))
    .union()
         .select(book).from(book).where(book.id.gt(42L))
    .end()
     .getQueryString();

Instead of:

String queryString = new BlazeJPAQuery<TestEntity>(entityManager, cbf)
        .union(
            select(book).from(book).where(book.id.lt(1337L)),
            select(book).from(book).where(book.id.gt(1337L))
        )
        .getQueryString();

Keep in mind that it should also support deeper nesting, which is problematic as with QueryDSL every builder is also its own expression. That means that we can only assign the right-handside of the set operation after the ongoing builder has ended.

This also makes it easier to use CTE binds that rely on bind expansion.