Ändra session saktar ner frågan genom Hibernate

UPPER() och BINARY_CI kan ge samma resultat men Oracle kan inte använda dem omväxlande. För att använda ett index och BINARY_CI måste du skapa ett index så här:

create index src_nlssort_index on src(nlssort(b, 'nls_sort=''BINARY_CI'''));

Exempeltabell och blandad casedata

create table src(b varchar2(100) not null);
insert into src select 'MiXeD CAse '||level from dual connect by level <= 100000;

Som standard kan upper()-predikatet utföra en intervallsökning på upper()-indexet

create index src_upper_index on src(upper(b));

explain plan for
select * from src where upper(b) = 'MIXED CASE 1';

select * from table(dbms_xplan.display(format => '-rows -bytes -cost -predicate 
    -note'));

Plan hash value: 1533361696

------------------------------------------------------------------
| Id  | Operation                   | Name            | Time     |
------------------------------------------------------------------
|   0 | SELECT STATEMENT            |                 | 00:00:01 |
|   1 |  TABLE ACCESS BY INDEX ROWID| SRC             | 00:00:01 |
|   2 |   INDEX RANGE SCAN          | SRC_UPPER_INDEX | 00:00:01 |
------------------------------------------------------------------

BINARY_CI och LINGUISTIC kommer inte att använda indexet

alter session set nls_sort='binary_ci';
alter session set nls_comp='linguistic';

explain plan for
select * from src where b = 'MIXED CASE 1';

select * from table(dbms_xplan.display(format => '-rows -bytes -cost -note'));

Plan hash value: 3368256651

---------------------------------------------
| Id  | Operation         | Name | Time     |
---------------------------------------------
|   0 | SELECT STATEMENT  |      | 00:00:02 |
|*  1 |  TABLE ACCESS FULL| SRC  | 00:00:02 |
---------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   1 - filter(NLSSORT("B",'nls_sort=''BINARY_CI''')=HEXTORAW('6D69786564
              2063617365203100') )

Funktionsbaserat index på NLSSORT() möjliggör genomsökning av indexintervall

create index src_nlssort_index on src(nlssort(b, 'nls_sort=''BINARY_CI'''));

explain plan for
select * from src where b = 'MIXED CASE 1';

select * from table(dbms_xplan.display(format => '-rows -bytes -cost -note'));

Plan hash value: 478278159

--------------------------------------------------------------------
| Id  | Operation                   | Name              | Time     |
--------------------------------------------------------------------
|   0 | SELECT STATEMENT            |                   | 00:00:01 |
|   1 |  TABLE ACCESS BY INDEX ROWID| SRC               | 00:00:01 |
|*  2 |   INDEX RANGE SCAN          | SRC_NLSSORT_INDEX | 00:00:01 |
--------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   2 - access(NLSSORT("B",'nls_sort=''BINARY_CI''')=HEXTORAW('6D69786564
              2063617365203100') )