Jooq 3.14.1 fetchLazy，postgres获取所有行

Question

我是新来的jooq，并试图与postgres使用fetchLazy。

我像下面这样修改了本文中提到的数据访问代码

// BookService.java
public List<Book> getBooks(){
    final List<Book> books = new ArrayList<>();
    ResultQuery<BookRecord> resQuery = context.selectFrom(Tables.BOOK).fetchSize(2);
    transactionRunner.readOnlyTransaction(() -> {
        try(final Cursor<BookRecord> bookRecords = resQuery.fetchLazy()) {
            while (bookRecords.hasNext()) {
                List<Book> into = bookRecords.fetch().into(Book.class);
                System.out.println("Num Records: " + into.size());
                books.addAll(into);
            }
        }
    });
    return books;
}

我的交易代码如下所示-

public class TransactionalRunner {
  private final PlatformTransactionManager manager;

  public void readOnlyTransaction(Runnable fn) {
    var template = new TransactionTemplate(manager);
    template.setIsolationLevel(TransactionDefinition.ISOLATION_READ_COMMITTED);
    template.execute(
        transactionStatus -> {
          fn.run();
          return null;
        });
  }
}

为了测试，我在数据库中添加了4条记录。即使fetchSize设置为2，我也会在一次获取中获取所有4条记录。

Num Records: 4

所有修改过的代码都放在github中。

有人能让我知道出了什么问题吗？

• Jooq版本3.14.1

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Answer 1

需要在fetchNext中指定大小。

// BookService.java
public List<Book> getBooks(){
    final List<Book> books = new ArrayList<>();
    ResultQuery<BookRecord> resQuery = context.selectFrom(Tables.BOOK).fetchSize(2);
    transactionRunner.readOnlyTransaction(() -> {
        try(final Cursor<BookRecord> bookRecords = resQuery.fetchLazy()) {
            while (bookRecords.hasNext()) {
                List<Book> into = bookRecords.fetchNext(2).into(Book.class);
                System.out.println("Num Records: " + into.size());
                books.addAll(into);
            }
        }
    });
    return books;
}