How to restrict displaytag to make database call on sorting? - sql

Question

I have a list of 1000 records, and I shown there 1000 records on page load using display tag.
I enabled sorting on some columns, and when I click on the table header to sort, display tag is making a database call and loading all 1000 records again.
How can we restrict to make database calls on sorting for display tag?
Because, we have loaded all the 1000 records, so could we make use of those list without loading the records again?

Answer 1

You are missing a fundamental: Pagination.
You should not load 1000 records at once; load 10 records at once instead (assuming 10 records is what you show in a page), and load the other 10 when changing page / sorting.
Filter them directly in the query (if you are using queries), for example, selecting page 3 (results from 21 to 30) in a query to a minimal "person table", ordered by name, would result it the following SQL:
Oracle
SELECT id, name, age
FROM ( SELECT id, name, age
FROM table_person
ORDER BY name )
WHERE ROWNUM BETWEEN 21 and 30
PostgreSQL
SELECT id, name, age
FROM table_person
ORDER BY name
LIMIT 10
OFFSET 20
and so on.
Be sure to read the documentation related to your database, and simply use query parameters to specify order by, starting row and ending row values.

Answer 2

you can use setFirstResults(), setMaxResults(),instead unnecessarily load all 1000 records.
divde per page max result shown 10 records only, and setFirstResult is restricted records first 5 from your records list.
Criteria cr= database_session.createCriteria(Records.class);
cr.addOrder(Order.desc("Recordsdate"));
cr.setFirstResult(5);
cr.setMaxResults(10);
all_records_list = (List<Records>) cr.list();