Pagination for update. Is it possible?

问题

Are they exist some methods to handle pagination for update? For example i have 100 rows of type:

@Id
private Integer id;
@Column
private boolean flag;
@Column
private Date last;

In start they looks like: id, false, null

And i have method in persistence:

@Query("SELECT t FROM Test t WHERE (t.last < :processStart OR t.last IS NULL)")
Page<Test> find(Pageable pageable, @Param("processStart") Date processStart);

I need take 10, set flag true and last = new Date() for each and save it back to DB.

Implementation looks like:

Date start = new Date();
for (int i = 0; i < 10; i++) {
    Pageable request = new PageRequest(i, 10, SortDirectuin.ASC, "id");
    Page page = testPersistence.find(request, start);
    page.getContext().forEach(t -> {
        ..huge part of another operation..
        t.setFlag(true);
        t.setLast(new Date());
        testPersistence.save(t);
    });
}

First page context should be with id: 0..9; Second: 10..19;

But in my case second page returns with id: 20..29;

And in end of pagination i lost half of data. Returns: 0..9, 20..29, 40..49, etc.

How to prevent this?

回答1:

I invented one bicycle method, and I try to explain it:

Pagination works like this:

1) row1 |        2) row1
   row2 | get1      row2
   row3 |           row3
   row4             row4 |
   row5             row5 | get2
   row6             row6 |
   row7             row7
   row8             row8
   row9             row9

But in my case my rows are changed and they do not comply with the request. So pagination looks like:

1) row1 |        2) row4
   row2 | get1      row5
   row3 |           row6
   row4             row7 |
   row5             row8 | get2
   row6             row9 |
   row7             
   row8             
   row9

Oops, i lose one pagination cycle set.

My solution is not increment page. And get first page all time It will be looks like:

1) row1 |        2) row4 |       3) row7 |
   row2 | get1      row5 | get1     row8 | get1
   row3 |           row6 |          row9 |
   row4             row7
   row5             row8
   row6             row9
   row7             
   row8             
   row9

In this case i don't lose any rows. But i repeat, it is so bicycle solution and it maybe does not work in another case.

来源：https://stackoverflow.com/questions/38324392/pagination-for-update-is-it-possible

标签

java

Spring

pagination