Module org.jooq
Package org.jooq.impl

Interface QOM.Dual

All Superinterfaces:
Fields, GroupField, Named, Qualified, QueryPart, RecordQualifier<Record>, SelectField<Record>, SelectFieldOrAsterisk, Serializable, Table<Record>, TableLike<Record>, Typed<Record>
Enclosing class:
QOM
public static interface QOM.Dual extends Table<Record>

  • Method Details

    • $traverse

      default <R> R $traverse(Traverser<?,R> traverser)
      Description copied from interface: QueryPart
      Traverser this QueryPart expression tree using a composable Traverser, producing a result.

      This offers a generic way to traverse expression trees to translate the tree to arbitrary other data structures. The simplest traversal would just count all the tree elements: 

      
 int count = CUSTOMER.NAME.eq(1).$traverse(0, (i, p) -> i + 1);

      The same can be achieved by translating the JDK Collector API to the Traverser API using Traversers.collecting(Collector). 

      
 CUSTOMER.NAME.eq(1).$traverse(Traversers.collecting(Collectors.counting()));

      Unlike a Collector, a Traverser is optimised for tree traversal, not stream traversal:

      • Is not designed for parallelism
      • It can Traverser.abort() traversal early when the result can be produced early (e.g. when running Traversers.containing(QueryPart), and a result has been found).
      • It can decide whether to Traverser.recurse() into a QueryPart subtree, or whether that is not necessary or even undesirable, e.g. to prevent entering new subquery scopes.
      • Unlike a Collector, which can use its Collector.accumulator() to accumulate each element only once, in tree traversal, it's desirable to be able to distinguish between accumulating an item Traverser.before() or Traverser.after() recursing into it. This is useful e.g. to wrap each tree node in XML opening and closing tags.

      This is a commercial jOOQ edition only feature.

      Specified by:
      $traverse in interface QueryPart

    • $replace

      default QueryPart $replace(Replacer replacer)
      Description copied from interface: QueryPart
      Traverse a QueryPart hierarchy and recursively replace its elements by alternatives.

      While replacing contents, this QueryPart isn't modified. Instead, a new object is returned.

      This is a commercial jOOQ edition only feature.

      Specified by:
      $replace in interface QueryPart