Quando usar os Function-Based Indexes?

Function-Based Indexes

Um dos problemas mais comuns encontrados num processo de tuning de instruções SQL são as operações FULL TABLE SCAN que muitas vezes são escolhidas pelo Otimizador por falta de opção já que não consegue utilizar um índice de uma determinada coluna pois o programador incluiu na cláusula WHERE uma função para essa coluna. A partir da versão Oracle 8i foi introduzido o recurso FUNCTION-BASED INDEXES que permitiu a criação de um índice onde os valores armazenados para a coluna indexada é o resultado da função incluída na cláusula WHERE o que possibilitou a utilização deste índice pelo Otimizador.

Por que usar FUNCTION-BASED INDEXES?

  1. É muito fácil utilizar este recurso basta criar um índice utilizando na coluna a mesma função presente na cláusula WHERE;
  2. Você pode utilizar este recurso como uma estratégia de Tuning de instrução SQL sem que seja necessário alterar uma linha de código;

Como habilitar o FUNCTION-BASED INDEXES?

  1. O usuário precisa ter os privilégios QUERY REWRITE e GLOBAL QUERY REWRITE para criar um FUNCTION-BASED INDEX numa tabela do seu esquema;
  2. Para o Otimizador utilizar FUNCTION-BASED INDEXES, é necessário definir os parâmetros abaixo a nível de sessão ou sistema:
    • QUERY_REWRITE_ENABLED=TRUE
    • QUERY_REWRITE_INTEGRITY=TRUSTED

 

Exemplo de FBI com UPPER()

 

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SQL > SELECT * FROM V$VERSION where rownum < 2;

BANNER
-------------------------------------------------------------------------------
Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - Production

SQL >
SQL > create index EMP_FNAME_IX2 on EMPLOYEES(FIRST_NAME);

Index created.

SQL > ALTER SESSION SET statistics_level=ALL;

Session altered.

SQL > SELECT /* tst101 */ FIRST_NAME, LAST_NAME, MANAGER_ID
  2    FROM EMPLOYEES
  3   WHERE UPPER(FIRST_NAME) = 'KIMBERELY';

FIRST_NAME           LAST_NAME                 MANAGER_ID
-------------------- ------------------------- ----------
Kimberely            Grant                            149

SQL >
SQL >
SQL >
SQL > column sql_id new_value m_sql_id
SQL > column child_number new_value m_child_no
SQL >
SQL > SELECT sql_id, child_number
  2    FROM v$sql
  3   WHERE sql_text LIKE '%tst101%'
  4     AND sql_text NOT LIKE '%v$sql%';

SQL_ID        CHILD_NUMBER
------------- ------------
c2a3qmrxcbnwj            0

SQL >
SQL >
SQL > SELECT *
  2    FROM TABLE (dbms_xplan.display_cursor ('&m_sql_id',&m_child_no,'basic iostats last'));

PLAN_TABLE_OUTPUT
---------------------------------------------------------------------------------------------------------------------------------------
EXPLAINED SQL STATEMENT:
------------------------
SELECT /* tst101 */ FIRST_NAME, LAST_NAME, MANAGER_ID   FROM EMPLOYEES
WHERE UPPER(FIRST_NAME) = :"SYS_B_0"

Plan hash value: 1445457117

-----------------------------------------------------------------------------------------
| Id  | Operation         | Name      | Starts | E-Rows | A-Rows |   A-Time   | Buffers |
-----------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT  |           |      1 |        |      1 |00:00:00.01 |       4 |
|*  1 |  TABLE ACCESS FULL| EMPLOYEES |      1 |      1 |      1 |00:00:00.01 |       4 |
-----------------------------------------------------------------------------------------

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

   1 - filter(UPPER("FIRST_NAME")=:SYS_B_0)


19 rows selected.

SQL >
SQL > create index EMP_FNAME_U_IX2 on EMPLOYEES(UPPER(FIRST_NAME));

Index created.

SQL > ALTER SESSION SET QUERY_REWRITE_ENABLED=TRUE;

Session altered.

SQL > ALTER SESSION SET QUERY_REWRITE_INTEGRITY=TRUSTED;

Session altered.

SQL > SELECT /* tst003 */ FIRST_NAME, LAST_NAME, MANAGER_ID
  2    FROM EMPLOYEES
  3   WHERE UPPER(FIRST_NAME) = 'KIMBERELY';

FIRST_NAME           LAST_NAME                 MANAGER_ID
-------------------- ------------------------- ----------
Kimberely            Grant                            149

SQL >
SQL >
SQL >
SQL > column sql_id new_value m_sql_id
SQL > column child_number new_value m_child_no
SQL >
SQL > SELECT sql_id, child_number
  2    FROM v$sql
  3   WHERE sql_text LIKE '%tst003%'
  4     AND sql_text NOT LIKE '%v$sql%';

SQL_ID        CHILD_NUMBER
------------- ------------
7u8aw59ma0v1k            0

SQL >
SQL >
SQL > SELECT *
  2    FROM TABLE (dbms_xplan.display_cursor ('&m_sql_id',&m_child_no,'basic iostats last'));

PLAN_TABLE_OUTPUT
---------------------------------------------------------------------------------------------------------------------------------------
EXPLAINED SQL STATEMENT:
------------------------
SELECT /* tst003 */ FIRST_NAME, LAST_NAME, MANAGER_ID   FROM EMPLOYEES
WHERE UPPER(FIRST_NAME) = :"SYS_B_0"

Plan hash value: 1892810479

---------------------------------------------------------------------------------------------------------
| Id  | Operation                   | Name            | Starts | E-Rows | A-Rows |   A-Time   | Buffers |
---------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT            |                 |      1 |        |      1 |00:00:00.01 |       3 |
|   1 |  TABLE ACCESS BY INDEX ROWID| EMPLOYEES       |      1 |      1 |      1 |00:00:00.01 |       3 |
|*  2 |   INDEX RANGE SCAN          | EMP_FNAME_U_IX2 |      1 |      1 |      1 |00:00:00.01 |       2 |
---------------------------------------------------------------------------------------------------------

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

   2 - access("EMPLOYEES"."SYS_NC00012$"=:SYS_B_0)


20 rows selected.

SQL >
SQL >
SQL > drop index EMP_FNAME_IX2;

Index dropped.

SQL > drop index EMP_FNAME_U_IX2;

Index dropped.

SQL >

 

Exemplo de FBI com TRUNC()

 

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SQL > @desc ORDERS
 Name                                Null?    Type
 ----------------------------------- -------- ------------------------
 ORDER_ID                            NOT NULL NUMBER(12)
 ORDER_DATE                          NOT NULL TIMESTAMP(6) WITH LOCAL
                                              TIME ZONE
 ORDER_MODE                                   VARCHAR2(8)
 CUSTOMER_ID                         NOT NULL NUMBER(6)
 ORDER_STATUS                                 NUMBER(2)
 ORDER_TOTAL                                  NUMBER(8,2)
 SALES_REP_ID                                 NUMBER(6)
 PROMOTION_ID                                 NUMBER(6)

SQL >
SQL >
SQL > ALTER SESSION SET statistics_level=ALL;

Session altered.

SQL >
SQL > SELECT /* tst001 */ ORDER_ID, ORDER_TOTAL, ORDER_DATE
  2    FROM ORDERS
  3   WHERE TRUNC(ORDER_DATE) = '02-OCT-07';

  ORDER_ID ORDER_TOTAL ORDER_DATE
---------- ----------- ---------------------------------------------------------------------------
      2454      6653.4 02-OCT-07 08.49.34.678340 PM
      2430     29669.9 02-OCT-07 09.18.36.663332 AM

2 rows selected.

SQL >
SQL >
SQL > column sql_id new_value m_sql_id
SQL > column child_number new_value m_child_no
SQL >
SQL > SELECT sql_id, child_number
  2    FROM v$sql
  3   WHERE sql_text LIKE '%tst001%'
  4     AND sql_text NOT LIKE '%v$sql%';

SQL_ID        CHILD_NUMBER
------------- ------------
04vjn6ffqf9ns            0

1 row selected.

SQL >
SQL >
SQL > SELECT *
  2    FROM TABLE (dbms_xplan.display_cursor ('&m_sql_id',&m_child_no,'basic iostats last'));

PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------------------------
EXPLAINED SQL STATEMENT:
------------------------
SELECT /* tst001 */ ORDER_ID, ORDER_TOTAL, ORDER_DATE   FROM ORDERS
WHERE TRUNC(ORDER_DATE) = :"SYS_B_0"

Plan hash value: 1275100350

--------------------------------------------------------------------------------------
| Id  | Operation         | Name   | Starts | E-Rows | A-Rows |   A-Time   | Buffers |
--------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT  |        |      1 |        |      2 |00:00:00.01 |       3 |
|*  1 |  TABLE ACCESS FULL| ORDERS |      1 |      1 |      2 |00:00:00.01 |       3 |
--------------------------------------------------------------------------------------

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

   1 - filter(TRUNC(INTERNAL_FUNCTION("ORDER_DATE"))=:SYS_B_0)


19 rows selected.

SQL >
SQL > ------------------------------------------------------------------------------------------------------------------------------------
SQL > ------------------------------------------------------------------------------------------------------------------------------------
SQL > create index ORD_ORDER_DATEF_IX on ORDERS(TRUNC("ORDER_DATE"));

Index created.

SQL > SELECT /* tst002 */ ORDER_ID, ORDER_TOTAL, ORDER_DATE
  2    FROM ORDERS
  3   WHERE TRUNC(ORDER_DATE) = '02-OCT-07';

  ORDER_ID ORDER_TOTAL ORDER_DATE
---------- ----------- ---------------------------------------------------------------------------
      2454      6653.4 02-OCT-07 08.49.34.678340 PM
      2430     29669.9 02-OCT-07 09.18.36.663332 AM

2 rows selected.

SQL >
SQL >
SQL > column sql_id new_value m_sql_id
SQL > column child_number new_value m_child_no
SQL >
SQL > SELECT sql_id, child_number
  2    FROM v$sql
  3   WHERE sql_text LIKE '%tst002%'
  4     AND sql_text NOT LIKE '%v$sql%';

SQL_ID        CHILD_NUMBER
------------- ------------
06nprpfdu35g0            0

1 row selected.

SQL >
SQL >
SQL > SELECT *
  2    FROM TABLE (dbms_xplan.display_cursor ('&m_sql_id',&m_child_no,'basic iostats last'));

PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------------------------
EXPLAINED SQL STATEMENT:
------------------------
SELECT /* tst002 */ ORDER_ID, ORDER_TOTAL, ORDER_DATE   FROM ORDERS
WHERE TRUNC(ORDER_DATE) = :"SYS_B_0"

Plan hash value: 2271898552

------------------------------------------------------------------------------------------------------------
| Id  | Operation                   | Name               | Starts | E-Rows | A-Rows |   A-Time   | Buffers |
------------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT            |                    |      1 |        |      2 |00:00:00.01 |       4 |
|   1 |  TABLE ACCESS BY INDEX ROWID| ORDERS             |      1 |      1 |      2 |00:00:00.01 |       4 |
|*  2 |   INDEX RANGE SCAN          | ORD_ORDER_DATEF_IX |      1 |      1 |      2 |00:00:00.01 |       2 |
------------------------------------------------------------------------------------------------------------

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

   2 - access("ORDERS"."SYS_NC00009$"=:SYS_B_0)


20 rows selected.

SQL >
SQL >
SQL >
SQL >
SQL > drop index ORD_ORDER_DATEF_IX;

Index dropped.

SQL >

 

Exemplo de FBI com DECODE()

 

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SQL> CREATE TABLE T1 AS SELECT * FROM ALL_OBJECTS WHERE OBJECT_TYPE IN ('SYNONYM','JAVA','INDEX','TABLE','EDITION');

Tabela criada.

SQL> CREATE INDEX T1_IDX ON T1(OBJECT_TYPE);

Índice criado.

SQL> exec dbms_stats.gather_table_stats(ownname => 'CURSO01',tabname => 'T1', ESTIMATE_PERCENT=>100 ,method_opt=>'FOR ALL INDEXED COLUMNS SIZE 254',cascade=>true);

Procedimento PL/SQL concluído com sucesso.

SQL> ALTER SESSION SET statistics_level=ALL;

Sessão alterada.

SQL> select /* tst001 */ OBJECT_NAME, CREATED
  2    from T1
  3   where DECODE(OBJECT_TYPE,'SYNONYM',10,'JAVA',20,'INDEX',30,'TABLE',40,'EDITION',50) = 50;

OBJECT_NAME                    CREATED
------------------------------ --------
ORA$BASE                       25/08/13

SQL>
SQL> column sql_id new_value m_sql_id
SQL> column child_number new_value m_child_no
SQL>
SQL> SELECT sql_id, child_number
  2    FROM v$sql
  3   WHERE sql_text LIKE '%tst001%'
  4     AND sql_text NOT LIKE '%v$sql%';

SQL_ID        CHILD_NUMBER
------------- ------------
46cgdpzwtnc60            0

SQL>
SQL>
SQL> SELECT *
  2    FROM TABLE (dbms_xplan.display_cursor ('&m_sql_id',&m_child_no,'basic iostats last'));
antigo   2:   FROM TABLE (dbms_xplan.display_cursor ('&m_sql_id',&m_child_no,'basic iostats last'))
novo   2:   FROM TABLE (dbms_xplan.display_cursor ('46cgdpzwtnc60',         0,'basic iostats last'))

PLAN_TABLE_OUTPUT
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
----------------------------------------------------------------------------------------------------
EXPLAINED SQL STATEMENT:
------------------------
select /* tst001 */ OBJECT_NAME, CREATED   from T1  where
DECODE(OBJECT_TYPE,'SYNONYM',10,'JAVA',20,'INDEX',30,'TABLE',40,'EDITION
'
,50) = 50

Plan hash value: 3617692013

---------------------------------------------------------------------------------------------
| Id  | Operation         | Name | Starts | E-Rows | A-Rows |   A-Time   | Buffers | Reads  |
---------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT  |      |      1 |        |      1 |00:00:00.02 |     592 |    589 |
|*  1 |  TABLE ACCESS FULL| T1   |      1 |    410 |      1 |00:00:00.02 |     592 |    589 |
---------------------------------------------------------------------------------------------

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

   1 - filter(DECODE("OBJECT_TYPE",'SYNONYM',10,'JAVA',20,'INDEX',30,'TABLE',40,'EDIT
              ION'
,50)=50)


21 linhas selecionadas.

SQL>
SQL> --------------------------------------------------------------------------------
SQL>
SQL> CREATE INDEX T1_FBI_IDX ON T1( DECODE(OBJECT_TYPE,'SYNONYM',10,'JAVA',20,'INDEX',30,'TABLE',40,'EDITION',50));

Índice criado.

SQL> SELECT INDEX_NAME, COLUMN_EXPRESSION
  2    FROM USER_IND_EXPRESSIONS
  3   WHERE INDEX_NAME='T1_FBI_IDX';

INDEX_NAME                     COLUMN_EXPRESSION
------------------------------ --------------------------------------------------------------------------------
T1_FBI_IDX                     DECODE("OBJECT_TYPE",'SYNONYM',10,'JAVA',20,'INDEX',30,'TABLE',40,'EDITION',50)

SQL>
SQL> ALTER SESSION SET QUERY_REWRITE_ENABLED=TRUE;

Sessão alterada.

SQL> ALTER SESSION SET QUERY_REWRITE_INTEGRITY=TRUSTED;

Sessão alterada.

SQL> select /* tst002 */ OBJECT_NAME, CREATED
  2    from T1
  3   where DECODE(OBJECT_TYPE,'SYNONYM',10,'JAVA',20,'INDEX',30,'TABLE',40,'EDITION',50) = 50;

OBJECT_NAME                    CREATED
------------------------------ --------
ORA$BASE                       25/08/13

SQL>
SQL> column sql_id new_value m_sql_id
SQL> column child_number new_value m_child_no
SQL>
SQL> SELECT sql_id, child_number
  2    FROM v$sql
  3   WHERE sql_text LIKE '%tst002%'
  4     AND sql_text NOT LIKE '%v$sql%';

SQL_ID        CHILD_NUMBER
------------- ------------
42s8f39knwb63            0

SQL>
SQL>
SQL> SELECT *
  2    FROM TABLE (dbms_xplan.display_cursor ('&m_sql_id',&m_child_no,'basic iostats last'));
antigo   2:   FROM TABLE (dbms_xplan.display_cursor ('&m_sql_id',&m_child_no,'basic iostats last'))
novo   2:   FROM TABLE (dbms_xplan.display_cursor ('42s8f39knwb63',         0,'basic iostats last'))

PLAN_TABLE_OUTPUT
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
----------------------------------------------------------------------------------------------------
EXPLAINED SQL STATEMENT:
------------------------
select /* tst002 */ OBJECT_NAME, CREATED   from T1  where
DECODE(OBJECT_TYPE,'SYNONYM',10,'JAVA',20,'INDEX',30,'TABLE',40,'EDITION
'
,50) = 50

Plan hash value: 2651436047

-------------------------------------------------------------------------------------------------------------
| Id  | Operation                   | Name       | Starts | E-Rows | A-Rows |   A-Time   | Buffers | Reads  |
-------------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT            |            |      1 |        |      1 |00:00:00.01 |       3 |      6 |
|   1 |  TABLE ACCESS BY INDEX ROWID| T1         |      1 |    410 |      1 |00:00:00.01 |       3 |      6 |
|*  2 |   INDEX RANGE SCAN          | T1_FBI_IDX |      1 |    164 |      1 |00:00:00.01 |       2 |      1 |
-------------------------------------------------------------------------------------------------------------

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

   2 - access("T1"."SYS_NC00016$"=50)


21 linhas selecionadas.

SQL> drop table t1;

Tabela eliminada.

SQL>

 

Exemplo de FBI com NVL()

 

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SQL> CREATE TABLE T1 AS SELECT * FROM ALL_OBJECTS;

Tabela criada.

SQL> UPDATE T1 SET OBJECT_TYPE = '' WHERE OBJECT_TYPE = 'CLUSTER';

10 linhas atualizadas.

SQL> COMMIT;

Commit concluído.

SQL> CREATE INDEX T1_IDX ON T1(OBJECT_TYPE);

Índice criado.

SQL> exec dbms_stats.gather_table_stats(ownname => 'CURSO01',tabname => 'T1', ESTIMATE_PERCENT=>100 ,method_opt=>'FOR ALL INDEXED COLUMNS SIZE 254',cascade=>true);

Procedimento PL/SQL concluído com sucesso.

SQL> ALTER SESSION SET statistics_level=ALL;

Sessão alterada.

SQL> select /* tst101 */ OBJECT_NAME, CREATED
  2    from T1
  3   where NVL(OBJECT_TYPE,'NULL') = 'NULL';

OBJECT_NAME                    CREATED
------------------------------ --------
C_COBJ#                        25/08/13
C_TS#                          25/08/13
C_FILE#_BLOCK#                 25/08/13
C_USER#                        25/08/13
C_OBJ#                         25/08/13
SMON_SCN_TO_TIME_AUX           25/08/13
C_OBJ#_INTCOL#                 25/08/13
C_TOID_VERSION#                25/08/13
C_MLOG#                        25/08/13
C_RG#                          25/08/13

10 linhas selecionadas.

SQL>
SQL> column sql_id new_value m_sql_id
SQL> column child_number new_value m_child_no
SQL>
SQL> SELECT sql_id, child_number
  2    FROM v$sql
  3   WHERE sql_text LIKE '%tst101%'
  4     AND sql_text NOT LIKE '%v$sql%';

SQL_ID        CHILD_NUMBER
------------- ------------
6v62jdzdh8jhy            0

SQL>
SQL>
SQL> SELECT *
  2    FROM TABLE (dbms_xplan.display_cursor ('&m_sql_id',&m_child_no,'basic iostats last'));
antigo   2:   FROM TABLE (dbms_xplan.display_cursor ('&m_sql_id',&m_child_no,'basic iostats last'))
novo   2:   FROM TABLE (dbms_xplan.display_cursor ('6v62jdzdh8jhy',         0,'basic iostats last'))

PLAN_TABLE_OUTPUT
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
----------------------------------------------------------------------------------------------------
EXPLAINED SQL STATEMENT:
------------------------
select /* tst101 */ OBJECT_NAME, CREATED   from T1  where
NVL(OBJECT_TYPE,'NULL') = 'NULL'

Plan hash value: 3617692013

------------------------------------------------------------------------------------
| Id  | Operation         | Name | Starts | E-Rows | A-Rows |   A-Time   | Buffers |
------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT  |      |      1 |        |     10 |00:00:00.01 |    1137 |
|*  1 |  TABLE ACCESS FULL| T1   |      1 |     11 |     10 |00:00:00.01 |    1137 |
------------------------------------------------------------------------------------

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

   1 - filter(NVL("OBJECT_TYPE",'NULL')='NULL')


19 linhas selecionadas.

SQL>
SQL> --------------------------------------------------------------------------------
SQL>
SQL> CREATE INDEX T1_FBI_IDX ON T1( NVL(OBJECT_TYPE,'NULL') );

Índice criado.

SQL>
SQL> SELECT INDEX_NAME, COLUMN_EXPRESSION
  2    FROM USER_IND_EXPRESSIONS
  3   WHERE INDEX_NAME='T1_FBI_IDX';

INDEX_NAME                     COLUMN_EXPRESSION
------------------------------ --------------------------------------------------------------------------------
T1_FBI_IDX                     NVL("OBJECT_TYPE",'NULL')

SQL>
SQL> ALTER SESSION SET QUERY_REWRITE_ENABLED=TRUE;

Sessão alterada.

SQL> ALTER SESSION SET QUERY_REWRITE_INTEGRITY=TRUSTED;

Sessão alterada.

SQL> select /* tst102 */ OBJECT_NAME, CREATED
  2    from T1
  3   where NVL(OBJECT_TYPE,'NULL') = 'NULL';

OBJECT_NAME                    CREATED
------------------------------ --------
C_COBJ#                        25/08/13
C_TS#                          25/08/13
C_FILE#_BLOCK#                 25/08/13
C_USER#                        25/08/13
C_OBJ#                         25/08/13
SMON_SCN_TO_TIME_AUX           25/08/13
C_OBJ#_INTCOL#                 25/08/13
C_TOID_VERSION#                25/08/13
C_MLOG#                        25/08/13
C_RG#                          25/08/13

10 linhas selecionadas.

SQL>
SQL> column sql_id new_value m_sql_id
SQL> column child_number new_value m_child_no
SQL>
SQL> SELECT sql_id, child_number
  2    FROM v$sql
  3   WHERE sql_text LIKE '%tst102%'
  4     AND sql_text NOT LIKE '%v$sql%';

SQL_ID        CHILD_NUMBER
------------- ------------
5ymy60w0vy796            0

SQL>
SQL>
SQL> SELECT *
  2    FROM TABLE (dbms_xplan.display_cursor ('&m_sql_id',&m_child_no,'basic iostats last'));
antigo   2:   FROM TABLE (dbms_xplan.display_cursor ('&m_sql_id',&m_child_no,'basic iostats last'))
novo   2:   FROM TABLE (dbms_xplan.display_cursor ('5ymy60w0vy796',         0,'basic iostats last'))

PLAN_TABLE_OUTPUT
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
----------------------------------------------------------------------------------------------------
EXPLAINED SQL STATEMENT:
------------------------
select /* tst102 */ OBJECT_NAME, CREATED   from T1  where
NVL(OBJECT_TYPE,'NULL') = 'NULL'

Plan hash value: 2651436047

-------------------------------------------------------------------------------------------------------------
| Id  | Operation                   | Name       | Starts | E-Rows | A-Rows |   A-Time   | Buffers | Reads  |
-------------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT            |            |      1 |        |     10 |00:00:00.01 |      10 |      7 |
|   1 |  TABLE ACCESS BY INDEX ROWID| T1         |      1 |    789 |     10 |00:00:00.01 |      10 |      7 |
|*  2 |   INDEX RANGE SCAN          | T1_FBI_IDX |      1 |    316 |     10 |00:00:00.01 |       3 |      7 |
-------------------------------------------------------------------------------------------------------------

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

   2 - access("T1"."SYS_NC00016$"='NULL')


20 linhas selecionadas.

SQL>
SQL> drop table t1;

Tabela eliminada.

SQL>
Title of the document

Ajudo DBAs e analistas de sistema a se destacarem em suas empresas

e obter um crescimento mais acelerado em suas carreiras, quer saber mais click no link abaixo:

 

Conclusão

Nesse artigo ilustramos o poder do recurso FUNCTION-BASED INDEXES com alguns exemplos, existem outras possibilidades de utilização desse recurso, é notório o ganho de performance das instruções SQL depois que passam a utilizar um FBI, basta observar a quantidade de blocos acessados no plano de execução antes e depois da criação e utilização do FBI.

 

 

Referências

https://docs.oracle.com/cd/E11882_01/appdev.112/e41502/adfns_indexes.htm#ADFNS00505

 
 
Promo-D75L

video-02
 
 
 
 
 
 
 
 
 
 
 
 
 
 

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