I'm using spring jpa with hibernate. When I use the pagination with sorting (typically in tables) the Oracle10gDialect generates the following SQL
select row_.*, rownum rownum_ from (
select table_.tablefield1, table_.tablefield2, table_.tablefield3...
from table table_ where <condition>
order by table_tablefield1 desc
) row_ where rownum <= 5
According to this explanation, the order by is in that case not considered as the rownum changes the order of the subquery. And in fact I'm experiencing the issue. Everything works well if I don't put any sorting field.
I opened a bug in Hibernate ORM but no feedback since more than 6 months. Anybody can help?
Environment Spring boot 2.2.0, Java 8, Linux, Oracle 19.0.0.0.0
REMARK! This question does not duplicate this one because I can't change the SQL generated by hibernate. Please check the tags before marking as duplicate.
CodePudding user response：
There is nothing wrong with the syntax above. It works correctly
SQL> select * from emp;
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
7369 SMITH CLERK 7902 17-DEC-80 800 20
7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30
7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30
7566 JONES MANAGER 7839 02-APR-81 2975 20
7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30
7698 BLAKE MANAGER 7839 01-MAY-81 2850 30
7782 CLARK MANAGER 7839 09-JUN-81 2450 10
7788 SCOTT ANALYST 7566 09-DEC-82 3000 20
7839 KING PRESIDENT 17-NOV-81 5000 10
7844 TURNER SALESMAN 7698 08-SEP-81 1500 30
7876 ADAMS CLERK 7788 12-JAN-83 1100 20
7900 JAMES CLERK 7698 03-DEC-81 950 30
7902 FORD ANALYST 7566 03-DEC-81 3000 20
7934 MILLER CLERK 7782 23-JAN-82 1300 10
14 rows selected.
SQL>
SQL> select * from emp
2 order by hiredate desc;
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
7876 ADAMS CLERK 7788 12-JAN-83 1100 20
7788 SCOTT ANALYST 7566 09-DEC-82 3000 20
7934 MILLER CLERK 7782 23-JAN-82 1300 10
7902 FORD ANALYST 7566 03-DEC-81 3000 20
7900 JAMES CLERK 7698 03-DEC-81 950 30
7839 KING PRESIDENT 17-NOV-81 5000 10
7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30
7844 TURNER SALESMAN 7698 08-SEP-81 1500 30
7782 CLARK MANAGER 7839 09-JUN-81 2450 10
7698 BLAKE MANAGER 7839 01-MAY-81 2850 30
7566 JONES MANAGER 7839 02-APR-81 2975 20
7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30
7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30
7369 SMITH CLERK 7902 17-DEC-80 800 20
14 rows selected.
SQL>
SQL> select row_.*, rownum rownum_ from (
2 select * from emp
3 order by hiredate desc
4 ) row_ where rownum <= 5;
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO ROWNUM_
---------- ---------- --------- ---------- --------- ---------- ---------- ---------- ----------
7876 ADAMS CLERK 7788 12-JAN-83 1100 20 1
7788 SCOTT ANALYST 7566 09-DEC-82 3000 20 2
7934 MILLER CLERK 7782 23-JAN-82 1300 10 3
7900 JAMES CLERK 7698 03-DEC-81 950 30 4
7902 FORD ANALYST 7566 03-DEC-81 3000 20 5
5 rows selected.
Perhaps you are referring to getting subsequent pages (2,3,4...) - if that is the case, we'd need to see the query generated for that.
CodePudding user response：
I do believe the SQLs generated by HBN to get both first and next pages are correct. It is more likely you are actually facing with sort stability issue: if some records has the same value of column you are ordering by, we can say nothing about their order, and oracle can't say as well, to make sort stable you need to add something unique (i.e. id) to order by clause.
select row_.*, rownum rownum_ from (
select table_.tablefield1, table_.tablefield2, table_.tablefield3...
from table table_ where <condition>
order by table_.tablefield1 desc, table_.id
) row_ where rownum <= 5
You might not facing with similar issue in other DBs because other DBs might use clustered index to support PK.
And yes, "modern syntax" won't solve sort stability issue.