eclipselink jpa条件参考未映射列 [英] eclipselink jpa criteria reference unmapped column

问题描述

在编写jpql查询时，我可以使用COLUMN（）引用未映射的列（我知道它是特定于eclipselink的）。
使用javax.persistence.criteria.CriteriaBuilder，javax.persistence.criteria.Predicate等构建条件时，有什么方法可以引用未映射的列？

when writing jpql queries I can reference not mapped columns with COLUMN() (I know it is eclipselink specific). Is there any way I can reference unmapped column when building criteria using javax.persistence.criteria.CriteriaBuilder, javax.persistence.criteria.Predicate, etc?

我面临的问题：我有带有全文搜索列的postgresql表。我不希望将其映射到实体对象，但我想在查询中使用它（并且我还需要使用CriteriaBuilder进行查询）。

The problem I am facing: I have postgresql table with full text search column. I do not want it to be mapped to entity objects but I qould like to use is in queries (and I need also queries using CriteriaBuilder).

编辑：代码示例

我有一张表格：X（id整数，名称varchar，fts tsvector）

I have a table: X (id integer, name varchar, fts tsvector)

fts列是全文搜索索引数据。
我需要没有 fts属性的实体类，例如：

"fts" column is full text search index data. I need entity class without "fts" attribute, like:

@Entity class X {
    @Id Integer id;
    @Column String name;
}

这样就永远不会获取fts数据（以提高性能），但是我需要能够查询该列。我可以使用jpql做到这一点：$ b​​ $ b从X t选择X t WHERE COLUMN（'fts'，t）不为空；

so that fts data is never fetched (for performance), but I need to be able to query that column. I can do this with jpql: SELECT t FROM X t WHERE COLUMN('fts', t) IS NOT NULL;

但是如何引用这样建立类似以下条件的列：

but how can I reference such column when building criteria like:

Specification<Fts> spec = new Specification<Fts>() {
        @Override
        public Predicate toPredicate(Root<Fts> root, CriteriaQuery<?> query, CriteriaBuilder builder) {
            return builder.notNull(root.<String>get("fts"));
        }
    };

其他选择：
如何在实体类中添加引用表列但从不添加的属性拿来？我尝试添加@Basic（fetchType = FetchType.LAZY），但是它不起作用，并且在查询时获取了值...

other choice: How to add attribute in entity class that reference table column but is never fetched? I tried adding @Basic(fetchType = FetchType.LAZY) but it does not work and value is fetched upon query...

推荐答案

Ok. I managed to solve it this way:

Specification<Fts> spec = new Specification<Fts>() {
        @Override
        public Predicate toPredicate(Root<Fts> root, CriteriaQuery<?> query, CriteriaBuilder builder) {
            JpaCriteriaBuilder cb = (JpaCriteriaBuilder) builder;
            List<String> args = new ArrayList();
            args.add("FTS query");

            javax.persistence.criteria.Expression<Boolean> expr = cb.fromExpression(
              cb.toExpression(
                cb.function("", Boolean.class, cb.fromExpression(((RootImpl) root).getCurrentNode().getField("fts")))
              )
              .sql("? @@ to_tsquery(?)", args)
            );
            // getField() allows to reference column not mapped to Entity

            query.where(expr);

            return null; // or return cb.isTrue(expr); and then not need to set query.where()
        }
    };

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