Pager

The Pager class is used for pagination. It holds data about a page request. For example you can call a search method like this:

Pager pager = new Pager();
// limit results to 5
pager.setLimit(5);
// sort by the 'tag' field
pager.setSortby("tag");
// descending order
pager.setDesc(true);
// last key special field
pager.setLastKey("1234");
List<Tag> tags = search.findTags("tag1", pager);
// the total number of tags for the query
int tagCount = pager.getCount();

The Pager class has a special string field lastKey for storing the last id for scrolling pagination queries. Usually scrolling is used in NoSQL databases, where in order to get a page of results, you have to provide the last key from the previous page.

Note

The fields page and limit are constrained by para.max_pages = 1000 and para.max_page_limit = 256. The first controls the maximum page number, and the second one sets the maximum results per page (i.e. the maximum value which the limit parameter can have).

Pager objects are used primarily in combination with search queries and allow you to limit the results of a query. When using ParaClient in combination with Pager, the client will automatically set the pager.lastKey property. To use the standard pagination mode, you must explicitly set the pager.page property:

// fetch page 1
paraClient.findQuery("*", pager);
pager.setPage(2);

// fetch page 2
paraClient.findQuery("*", pager);
pager.setPage(3);
//  and so on...

For “search after”, or “deep” pagination the page property is omitted:

// fetch page 1
paraClient.findQuery("*", pager);

// fetch page 2
paraClient.findQuery("*", pager);
//  and so on...

And here’s an example for reading all object of type “cat” using deep pagination (“search after”):

Pager pager = new Pager(1, "_docid", false, 10_000);
List<Cat> cats = new LinkedList<>();
List<Cat> catsPage;
do {
  catsPage = Para.getSearch().findQuery("cat", "*", pager);
  cats.addAll(catsPage);
} while (!catsPage.isEmpty());