oracle faster paging query
I don't actually have availability of Oracle now but the best SQL query for paging is the following for sure
select *
from (
select rownum as rn, a.*
from (
select *
from my_table
order by ....a_unique_criteria...
) a
)
where rownum <= :size
and rn > (:page-1)*:size
http://www.oracle.com/technetwork/issue-archive/2006/06-sep/o56asktom-086197.html
To achieve a consistent paging you should order rows using a unique criteria, doing so will avoid to load for page X a row you already loaded for a page Y ( !=X ).
EDIT:
1) Order rows using a unique criteria means to order data in way that each row will keep the same position at every execution of the query
2) An index with all the expressions used on the ORDER BY clause will help getting results faster, expecially for the first pages. With that index the execution plan choosen by the optimizer doesn't needs to sort the rows because it will return rows scrolling the index by its natural order.
3) By the way, the fastests way to page result from a query is to execute the query only once and to handle all the flow from the application side.
Take a look at the execution plans, example with 1000 rows:
SELECT *
FROM (SELECT ROWNUM rnum
,a.*
FROM (SELECT *
FROM members) a
WHERE ROWNUM <= endrow#)
WHERE rnum > startrow#;
--------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
--------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1000 | 39000 | 3 (0)| 00:00:01 |
|* 1 | VIEW | | 1000 | 39000 | 3 (0)| 00:00:01 |
| 2 | COUNT | | | | | |
|* 3 | FILTER | | | | | |
| 4 | TABLE ACCESS FULL| MEMBERS | 1000 | 26000 | 3 (0)| 00:00:01 |
--------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter("RNUM">"STARTROW#")
3 - filter("MEMBERS"."ENDROW#">=ROWNUM)
And 2.
SELECT *
FROM (SELECT ROWNUM rnum
,a.*
FROM (SELECT *
FROM members) a)
WHERE rnum BETWEEN startrow# AND endrow#;
-------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
-------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1000 | 39000 | 3 (0)| 00:00:01 |
|* 1 | VIEW | | 1000 | 39000 | 3 (0)| 00:00:01 |
| 2 | COUNT | | | | | |
| 3 | TABLE ACCESS FULL| MEMBERS | 1000 | 26000 | 3 (0)| 00:00:01 |
-------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter("RNUM"<="ENDROW#" AND "RNUM">="STARTROW#")
Out of that I'd say version 2 could be slightly faster as it includes one step less. But I don't know about your indexes and data distribution so it's up to you to get these execution plans yourself and judge the situation for your data. Or simply test it.