Where to find info on function based indexes

Hello,
Using Oracle 11.2, can someone tell me where I can find information about existing Function Based indexes in my database?
I want to shrink the unused space on a table, but there is a FB index that I have to drop in order to shrink the space.
Then, I need to recreate it after I shrink the space.
But how do I find out what functions the index is created to be used for?
I've already looked at dba_indexes, and dba_ind_expressions with no luck.
I see the index, but I don't see what the functions are that are being applied for the FB index.
Thanks in advance.

Yes, this is why I'm also confused, which is what I pointed out in the first entry of this thread.
Notice here:
SQL> select index_name, index_type from dba_indexes where table_name = 'TQR1';
INDEX_NAME                     INDEX_TYPE
IDX$$_0FFD0001                 NORMAL
IDX$$_211C0002                 NORMAL
TQR1_C3                        FUNCTION-BASED NORMAL
. . .Now, let's confirm another way....
select OWNER, INDEX_NAME, INDEX_TYPE, TABLE_OWNER, TABLE_NAME
from dba_indexes where index_name = 'TQR1_C3';
OWNER      INDEX_NAME INDEX_TYPE                  TABLE_OWNER TABLE_NAME
TQ         TQR1_C3    FUNCTION-BASED NORMAL       TQ           TQR1
1 row selected.Now, let's show the selection from dba_ind_expressions...
INDEX_OWNER INDEX_NAME TABLE_OWNER TABLE_NAME COLUMN_EXPRESSI COLUMN_POSITION
TQ           TQR1_C3    TQ           TQR1       "C3"                          1I don't know the password for the TQ owner, so I'll have to wait until I can find that out before I can run DBMS_METADATA.

Similar Messages

Function based indexes info,pls let me know data dictionary table name?

Hi,
pls let me know,Where can we find Function based index information ,that is data dictionary table name,.
that is information like function used, column name.
Thanks,
KUmar.

all_ind_expressions

Function-based index with OR in the wher-clause

We have some problems with functin-based indexes and
the or-condition in a where-clause.
--We use Oracle 8i (8.1.7)
create table TPERSON(ID number(10),NAME varchar2(20),...);
create index I_NORMAL_TPERSON_NAME on TPERSON(NAME);
create index I_FUNCTION_TPERSON_NAME on TPERSON(UPPER(NAME));
The following two statements run very fast on a large table
and the execution-plan asure the usage of the indexes
(-while the session is appropriate configured and the table is analyzed):
1)     select count(ID) FROM TPERSON where upper(NAME) like 'MIL%';
2)     select count(ID) from TPERSON where NAME like 'Mil%' or (3=5);
In particular we see that a normal index is used while the where-clause contains
an OR-CONDITION.
But if we try the similarly select-statement
3)     select count(ID) FROM TPERSON where upper(NAME) like 'MIL%' or (3=5);
the CBO will not use the function-index I_FUNCTION_TPERSON_NAME and we have a full table scan in the execution-plan.
(This behavior we only expect with views but not with indexes.)
We ask for an advice like a hint, which enable the CBO-usage
of function-based indexes in connection with OR.
This problem seems to be artificial because it contains this dummy logic:
     or (3=5).
This steams from an prepared statement, where this kind of boolean
flag reduce the amount of different select-statements needed for
covering the hole business-logic, while using bind-variables for the
concrete query-parameters.
A more realistic (still boild down) version of our select-statement is:
select * FROM TPERSON
where (upper(NAME) like 'MIL%' or (NAME is null))
and (upper(FIRSTNAME) like 'MICH% or (FIRSTNAME is null))
and ...;
thank you for time..
email: [email protected]

In the realistic statement you write :
select * FROM TPERSON
where (upper(NAME) like 'MIL%' or (NAME is null))
and (upper(FIRSTNAME) like 'MICH% or (FIRSTNAME is null))
and ...;
as far as i know, NULL values are not indexed, "or (NAME is NULL)" have to generate a full table scan.
HTH
We have some problems with functin-based indexes and
the or-condition in a where-clause.
--We use Oracle 8i (8.1.7)
create table TPERSON(ID number(10),NAME varchar2(20),...);
create index I_NORMAL_TPERSON_NAME on TPERSON(NAME);
create index I_FUNCTION_TPERSON_NAME on TPERSON(UPPER(NAME));
The following two statements run very fast on a large table
and the execution-plan asure the usage of the indexes
(-while the session is appropriate configured and the table is analyzed):
1)     select count(ID) FROM TPERSON where upper(NAME) like 'MIL%';
2)     select count(ID) from TPERSON where NAME like 'Mil%' or (3=5);
In particular we see that a normal index is used while the where-clause contains
an OR-CONDITION.
But if we try the similarly select-statement
3)     select count(ID) FROM TPERSON where upper(NAME) like 'MIL%' or (3=5);
the CBO will not use the function-index I_FUNCTION_TPERSON_NAME and we have a full table scan in the execution-plan.
(This behavior we only expect with views but not with indexes.)
We ask for an advice like a hint, which enable the CBO-usage
of function-based indexes in connection with OR.
This problem seems to be artificial because it contains this dummy logic:
     or (3=5).
This steams from an prepared statement, where this kind of boolean
flag reduce the amount of different select-statements needed for
covering the hole business-logic, while using bind-variables for the
concrete query-parameters.
A more realistic (still boild down) version of our select-statement is:
select * FROM TPERSON
where (upper(NAME) like 'MIL%' or (NAME is null))
and (upper(FIRSTNAME) like 'MICH% or (FIRSTNAME is null))
and ...;
thank you for time..
email: [email protected]

Function-based Index and an OR-condition in the WHERE-clause

We have some problems with functin-based indexes and
the or-condition in a where-clause.
(We use oracle 8i (8.1.7))
create table TPERSON(ID number(10),NAME varchar2(20),...);
create index I_NORMAL_TPERSON_NAME on TPERSON(NAME);
create index I_FUNCTION_TPERSON_NAME on TPERSON(UPPER(NAME));
The following two statements run very fast on a large table
and the execution-plan asure the usage of the indexes
(-while the session is appropriate configured and the table is analyzed):
1)     select count(ID) FROM TPERSON where upper(NAME) like 'MIL%';
2)     select count(ID) from TPERSON where NAME like 'Mil%' or (3=5);
In particular we see that a normal index is used while the where-clause contains
an OR-CONDITION.
But if we try the similarly select-statement
3)     select count(ID) FROM TPERSON where upper(NAME) like 'MIL%' or (3=5);
the CBO will not use the function-index.
(This behavior we only expect with views but not with indexes.)
We ask for an advice like an hint, which enable the CBO-usage
of function-based indexes in connection with OR.
This problem seems to be artificial because it contains this dummy logic:
     or (3=5).
This steams from an prepared statement, where this kind of boolean
flag reduce the amount of different select-statements needed for
covering the hole business-logic, while using bind-variables for the
concrete query-parameters.
A more realistic (still boild down) version of our prepared select-statement run in
SQL Plus:
define x_name = 'MIL%';
define x_firstname = '';
select * FROM TPERSON
where (upper(NAME) like '&x_name' or ( '&x_name' = ''))
and (upper(FIRSTNAME) like '&x_firstname' or ('&x_firstname' = ''))
and ...;
In particular we dont refernce the tablecolumn , but the QUERY-Parameter
yield the second boolean value in the or-condition.
The problem is that this condition ('&x_name' = '') dont use any index.
thanks a lot for spending your time with this problem

Try
SELECT /*+ RULE */
as your hint. I don't have the book with me, but this last weekend I read a section about your very problem. The book was a Oracle Press gold cover about Oracle 8i Performance tuning. If you e-mail me I can quote you the chapter when I get home Friday.

Function Based Indexes - negative performance

Has anyone run across any cases where they have had issues with Function Based Indexes negatively impacting performance??
We are trying to use function based indexes in 9i (NLS_SORT=GENERIC_BASELETTER) and 10g (NLS_SORT=BINARY_CI) for case insensitivity.
We thought this was a decent solution until recently when testing with larger datasets. Any info is appreciated.
Thanks,

Just to clarify rreynoldson's first point:
All indexes will negatively impact inserts. Indexes, including function-based indexes, may or may not improve update and delete performance depending on whether the overhead of maintaining the index outweighs the benefit of being able to use the index to find the row(s) to update relatively quickly.
For user564260:
Assuming those parameters are set, make sure that you've gathered statistics on the function based index. If that doesn't resolve the problem, can you post a small test case that demonstrates the problem where you
- Create the table
- Create the indexes
- Populate it with data
- Run the query that you'd expect to use the FBI
- Post the explain plan
that would help us immensely.
Justin

Function based indexes on CLOB storage

On a 10gR2 database, with schema-less CLOB storage for an XMLType column:
(1) Can a function based index include a wildcard in the namespace ? Or do I need a new function based index for each specific namespace ?
(2) I must create a new function based index for each different element that I want an indexed search on ?
(3) What limit is there on the number of function based indexes per table ?
(4) I believe XQuery can include a wildcard for namespaces, but XPath 1.x can't. Can I create a function based index using XQuery, rather than XPath ?
Documents conforming to different versions of an XML schema will be present (schema versioning), but I want to search across all documents irrespective of a specific namespace - e.g. "Find any document with reference = 'some Value' , and amount = 1000".
CLOB storage is proposed, due to the need to handle documents from multiple versions of an XML schema. The knowledge of the XSD is not known at development time, but is user definable, and it must be possible to change the structure without system down time. Structured storage is not suitable, due to Oracle's requirement for downtime if the schema changes (CopyEvolve drops/recreates tables), and Oracle doesn't support schema collections, so you can't bind an XML column to multiple schemas.
Here is some sample code of what I'm trying to do:
create table BulkTest
ID NUMBER(10) not null primary key,
USERFIELDS XMLTYPE
create sequence S_BulkTest;
--Document conforming to version 1 of schema
INSERT INTO BulkTest(id, Userfields) VALUES
(S_BulkTest.Nextval,
'<?xml version="1.0" encoding="utf-8" ?>
<mt395 xmlns="urn:incident:mt395-1">
     <reference>FH12345678</reference>
     <relatedReference>FH23456789</relatedReference>
     <queries>Here is some query text.</queries>
     <narrative>Here is some narrative text.</narrative>
     <relatedMessageType>300</relatedMessageType>
     <relatedMessageDate>2005-03-29</relatedMessageDate>
     <direction>R</direction>
     <sessionNumber>1234</sessionNumber>
     <isn>123456</isn>
     <relatedMessageDescription>This is the deal where I bought USD 1 million for GBP at 1.76.</relatedMessageDescription>
     <otherParty>232332</otherParty>
</mt395>'
--Document conforming to version 2 of schema
INSERT INTO BulkTest(id, Userfields) VALUES
(S_BulkTest.Nextval,
'<?xml version="1.0" encoding="utf-8" ?>
<mt395 xmlns="urn:incident:mt395-2">
     <guid>0f9a08f6-b052-4693-baba-8f7dc881e7e8</guid>
     <reference>333333</reference>
     <queries>Another query</queries>
     <narrative>Some narrative</narrative>
     <direction>R</direction>
     <sessionNumber>1234</sessionNumber>
     <isn>223456</isn>
</mt395>'
--It seems I need to create a new index for each field I want to search on
create index iBulkTest_REFERENCE
on BulkTest
(extractValue(UserFields,'/mt395/reference', 'xmlns="urn:incident:mt395-1"'));
--And that a new index is required for each specifc namespace that is present
--Can't we include a wildcard in the namespace ?
create index iBulkTest_REFERENCE_2
on BulkTest
(extractValue(UserFields,'/mt395/reference', 'xmlns="urn:incident:mt395-2"'));
--If I want to query, I have to explicitly specify each namespace.
--Can't I specify a wildcard ?
--This will make it "fun" querying across namespaces!
select
id,
extractValue(UserFields,'/mt395/reference', 'xmlns="urn:incident:mt395-2"') As Reference,
t.userfields.getclobval() userfields
from bulktest t
WHERE extractValue(UserFields,'/mt395/reference', 'xmlns="urn:incident:mt395-2"') = '333333'

Andy
#1. You do not have scehma versioning here. Your model is totally incorrect. You shoud not change the namespace when versioning the XML Schema. You have 2 different and totally disjoint XML Schemas. The correct was to version, as distinct from evolve an XML Schema is to change the Schema Location Hint associated with your XML...
Eg
INSERT INTO BulkTest(id, Userfields) VALUES
(S_BulkTest.Nextval,
'<?xml version="1.0" encoding="utf-8" ?>
<mt395 xmlns="urn:incident:mt395" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="urn:incident:mt395 mt395-1.xsd">
<reference>FH12345678</reference>
<relatedReference>FH23456789</relatedReference>
<queries>Here is some query text.</queries>
<narrative>Here is some narrative text.</narrative>
<relatedMessageType>300</relatedMessageType>
<relatedMessageDate>2005-03-29</relatedMessageDate>
<direction>R</direction>
<sessionNumber>1234</sessionNumber>
<isn>123456</isn>
<relatedMessageDescription>This is the deal where I bought USD 1 million for GBP at 1.76.</relatedMessageDescription>
<otherParty>232332</otherParty>
</mt395>'
--Document conforming to version 2 of schema
INSERT INTO BulkTest(id, Userfields) VALUES
(S_BulkTest.Nextval,
'<?xml version="1.0" encoding="utf-8" ?>
<mt395 xmlns="urn:incident:mt395 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="urn:incident:mt395 mt395-2.xsd">
<guid>0f9a08f6-b052-4693-baba-8f7dc881e7e8</guid>
<reference>333333</reference>
<queries>Another query</queries>
<narrative>Some narrative</narrative>
<direction>R</direction>
<sessionNumber>1234</sessionNumber>
<isn>223456</isn>
</mt395>'
This is the correct way of versioning an XML Schema. THe namespace stays the same, the SchemaLocationHint in the SchemaLocation tag changes.
Bear in mind that if you use the technique you are currently using you will make any path expressions you need to write absolutely unmaintaining and the processing of them very inefficient.
Some questions to consider
Node 'X' in namespace 'X' is never the same as Node 'X' in namespace 'Y'.
How would you write an Xpath or XQuery that targetted multiple versions, but not all versions ?
What happens if you have other documents that are really in a different namespace ? Using wildcards can you differentiate them..
From the problem you are describing and the terminolgy you are using it looks like you've been an early customer of Yukon. MSFT clearly didn't understand schema versioning in the early beta releases and used the 'change the namespace' schema for modelling schema versioning.
We do have some technology coming down the pipe which can address the issue, regardless of whether or not it is too late for you to correct the versioning scheme you have selected. However I cannot discuss that in a public forum. If you want to learn about these features and are prepared to enter an NDA with Oracle in order to do so please contact me directly. You can do this a number of ways...
Guess my email address @oracle.com
Post your email address here and I'll delete the post as soon as I have it..
Update your OTN Forum profile to include your email address
Open a TAR and post the tar number here. You can then softclose the tar as this is simply a method for me to get your contact info.

Function-based indexes don't seem to work in Oracle 8.1.5?

Hi,
What gives? What am I doing wrong? I have a table AIRPORT with a column (varchar2(64)) which I have specified a function based index for, but I can't get SQL wueries to use it!!!! the following SQL executes a FULL TABLE SCAN:
select /*+ index (a idx_upper_cityname) */ *
from airport a
where nls_upper(cityName) = 'dfdf'
...as does...
select *
from airport a
where nls_upper(cityName) = 'dfdf'
Table and index code is as follows:
CREATE TABLE airport
id NUMBER NOT NULL,
citycode VARCHAR2(3) NOT NULL,
cityname VARCHAR2(64) NOT NULL,
state VARCHAR2(2),
country VARCHAR2(2) NOT NULL,
region CHAR(1),
airportcode VARCHAR2(3) NOT NULL,
airportname VARCHAR2(64),
code VARCHAR2(4)
drop index idx_upper_cityname
CREATE INDEX idx_upper_cityname ON airport nls_upper(substr(cityName, 0, 64) )
Environment is as follows:
Oracle8i v8.1.5 running on WinNT v4.0 (SP 5)
Client is running on the same machine
thanks in advance,
Alexander

New data point: when I set the handler in my logging.properties file thusly,
org.apache.catalina.core.ContainerBase.[Catalina].[info-dev].[/infoisland].level = ALL
org.apache.catalina.core.ContainerBase.[Catalina].[info-dev].[/infoisland].handlers = java.util.logging.ConsoleHandlerI get 0 bytes in the info-dev log (which used to have the aforementioned expception in it). Where is my console going?

Segment Shrinking script erroring out due to Function based indexes, lobs,.

DB version:10gR2
Following is a script i made for freeing up(SHRINK ing and resetting HWM) the space in Tables and its indexes. Due to the existence of LOB Segments and Tables with Function based indexes, this script was erroring out. So i was wondering if there is a way to find out the segments which are eligible/not eligible for Shrinking so that i could make necessary changes to the below script.
create or replace procedure freeup_space
is
type v_segment_type is table of varchar2(30) index by binary_integer;
v_segment v_segment_type;
begin
select segment_name bulk collect into v_segment
               from user_segments
               where segment_type in ('TABLE')
                 and segment_name not like 'BIN%';
for i in v_segment.first..v_segment.last loop
execute immediate 'alter table ' || v_segment(i) ||' enable row movement';
dbms_output.put_line('Table '||v_segment(i)||'''s row movement enabled');
execute immediate 'alter table ' || v_segment(i) ||' shrink space cascade';
execute immediate 'alter table ' || v_segment(i) ||' deallocate unused';
end loop;
end;
/

You can use USER_LOBS views to look for LOB columns in the segments and ALL_INDEXES.INDEX_TYPE tells if the index is function based index or not.
Message was edited by:
Pierre Forstmann

Limit on number of function based indexes ?

What is the limit on the number of function based indexes that can exist on a table ?
I haven't been able to find this info in the Oracle docs yet . I'd RTFM, but which one ? There's so many ! :-)

http://download-east.oracle.com/docs/cd/B19306_01/server.102/b14237/limits003.htm#sthref4186

Why do we need query rewrite enabled for a function-based index?

Oracle 9i
========
I have searched a few sites but could not find any content on it. The question is why do we need to implement query rewrite enabled when we are trying out a function-based index?
Thanks in advance.

You don't, that's a legacy requirement from the early days of function based indexes in Oracle 8i. Here's a quick example running under 9.2.0.6
drop table t1;
create table t1 as
select
from
     all_objects
where
     rownum <= 30000
create or replace function pl_func(i_vc     varchar2)
return varchar2
deterministic
as
begin
     return soundex(i_vc);
end;
-- set the worst case scenario
alter session set query_rewrite_enabled = false;
alter session set query_rewrite_integrity = enforced;
create index t1_i1 on t1(pl_func(object_name));
execute dbms_stats.gather_table_stats(user, 't1')
set autotrace traceonly explain
select
     object_name
from t1
where pl_func(object_name) = 'T513'
set autotrace offResults (after set feedback off)
SQL> @temp
Execution Plan
Plan hash value: 1429545322
| Id | Operation                   | Name | Rows | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT            |       |    27 |   675 |    10   (0)| 00:00:01 |
|   1 | TABLE ACCESS BY INDEX ROWID| T1    |    27 |   675 |    10   (0)| 00:00:01 |
|* 2 |   INDEX RANGE SCAN          | T1_I1 |    27 |       |     1   (0)| 00:00:01 |
Predicate Information (identified by operation id):
   2 - access("TEST_USER"."PL_FUNC"("OBJECT_NAME")='T513')
SQL> spool offRegards
Jonathan Lewis
http://jonathanlewis.wordpress.com
http://www.jlcomp.demon.co.uk

Creation of function based index using escape

Hello,
I have the following SQL, sometimes performing bad:
SELECT DISTINCT UPPER(A.PROCESSIDCODE), UPPER(A.RULENAME), CHARSET
FROM XIB_DETECT A, XIB_PROCESSIDPROPERTIES B, XIB_RULES C
WHERE ( A.KEY1 = :P1 OR ( :P1 like REPLACE(REPLACE(REPLACE(REPLACE(KEY1,'%', '\%'),'_', '\_'),'?', '_'),'*','%') escape '\' AND A.REGFLAGS1 = 'Y') OR A.KEY1 = '*' AND A.REGFLAGS1 = 'Y')
AND (A.KEY2 = :P2 OR ( :P2 like REPLACE(REPLACE(REPLACE(REPLACE(KEY2,'%', '\%'),'_', '\_'),'?', '_'),'*','%') escape '\' AND A.REGFLAGS2 = 'Y') OR (A.KEY2 IS NULL AND A.REGFLAGS2 IS NULL ) )
AND (A.KEY3 = :P3 OR ( :P3 like REPLACE(REPLACE(REPLACE(REPLACE(KEY3,'%', '\%'),'_', '\_'),'?', '_'),'*','%') escape '\' AND A.REGFLAGS3 = 'Y') OR (A.KEY3 IS NULL AND A.REGFLAGS3 IS NULL ) )
AND (A.KEY4 = :P4 OR ( :P4 like REPLACE(REPLACE(REPLACE(REPLACE(KEY4,'%', '\%'),'_', '\_'),'?', '_'),'*','%') escape '\' AND A.REGFLAGS4 = 'Y') OR (A.KEY4 IS NULL AND A.REGFLAGS4 IS NULL ) )
AND (A.KEY5 = :P5 OR ( :P5 like REPLACE(REPLACE(REPLACE(REPLACE(KEY5,'%', '\%'),'_', '\_'),'?', '_'),'*','%') escape '\' AND A.REGFLAGS5 = 'Y') OR (A.KEY5 IS NULL AND A.REGFLAGS5 IS NULL ) )
AND (A.KEY6 IS NULL OR A.KEY6 = '*' AND REGFLAGS6 = 'Y')
AND (A.KEY7 IS NULL OR A.KEY7 = '*' AND REGFLAGS7 = 'Y')
AND (A.KEY8 IS NULL OR A.KEY8 = '*' AND REGFLAGS8 = 'Y')
AND (A.KEY9 IS NULL OR A.KEY9 = '*' AND REGFLAGS9 = 'Y')
AND (A.KEY10 IS NULL OR A.KEY10 = '*' AND REGFLAGS10 = 'Y')
AND ( ( A.PROCESSIDCODE IS NOT NULL AND UPPER(A.PROCESSIDCODE) = UPPER(B.PROCESSIDCODE) AND A.XLEVEL = B.XLEVEL AND B.ACTIVEFLAG = 'Y' )
OR ( A.RULENAME IS NOT NULL AND UPPER(A.RULENAME) = UPPER(C.RULENAME) AND A.XLEVEL = C.XLEVEL AND C.ACTIVEFLAG = 'Y' ) );
Now I want to create a function based index on the key1 column:
CREATE INDEX xib_detect_ix ON xib_detect (REPLACE(REPLACE(REPLACE(REPLACE(KEY1,'%', '\%'),'_', '\_'),'?', '_'),'*','%') escape '\') TABLESPACE ... ONLINE;
However, this is not working with "escape" '\', throwing: ORA-00907: missing right parenthesis
Any idea how to create an index on this construct with "escape"?
Database version is 10.2.0.3.
Thanks a lot.
Regards
Oliver

Hi,
You can get the "missing right parenthesis" error for many different syntax errors.
In this case, you really are missing a right parenthesis. Your statement has 5 left '('s, but only 4 right ')'s. It's easy to see this if you format your code:
CREATE INDEX xib_detect_ix
ON xib_detect ( REPLACE ( REPLACE ( REPLACE ( REPLACE ( KEY1
escape '\'
ESCAPE is an option that you can use with the LIKE operator. It gives you a mechanism for cancelling the special meaning of symbols like '%'. You're not using the LIKE operator to create the index. You're only using REPLACE, and no characters have any special meaning in REPLACE, so there's no way (or reason) to escape them. Use ESCAPE in queries that use LIKE, when appropriate.

FUNCTION-BASED INDEX ( ORACLE 8I NEW FEATURE )

제품 : ORACLE SERVER
작성날짜 : 2004-08-16
FUNCTION-BASED INDEX ( ORACLE 8I NEW FEATURE )
==============================================
SCOPE
10g Standard Edition(10.1.0) 이상 부터 Function-based Index 기능이 지원된다.
Explanation
1. 개요
     Function-based index는, 함수(function)이나 수식(expression)으로 계산
된 결과에 대해 인덱스를 생성하여 사용할 수 있는 기능을 제공한다.
     질의 수행 시 해당 함수나     수식을 처리하여     결과를 가져 오는 것이 아니라,
     인덱스 형태로 존재하는 미리 계산되어 있는 결과를 가지고 처리하므로
     성능 향상을 기할 수 있다.
2. 제약사항
1) aggregate function 에 대한 function-based index 생성 불가.
(예 : sum(...) )
2) LOB, REF, nested table 컬럼에 대한 function-based index 생성 불가.
3. 주요 특징
     1) cost-based optimizer에 의해 사용됨.
     2) B*Tree / bitmap index로 생성 가능.
     3) 산술식 (arithmetic expression), PLSQL function, SQL built-in
function 등에 적용 가능.
     4) 함수나 수식으로 처리된 결과에 대한 range scan 가능
     5) NLS SORT 지원
     6) SELECT/DELETE를 할 때마다 함수나 수식의 결과를 계산하는 것이 아니라
     INSERT/UPDATE 시 계산된 값을 인덱스에 저장.
     7) 질의 속도 향상
     8) object column이나 REF column에 대해서는 해당 object에 정의된
     method에 대해 function-based index 생성 가능.
4. 생성 방법
     CREATE [UNIQUE | BITMAP ] INDEX <index_name>
     ON <tablename> (<index-expression-list>)
     <index-expression-list> -> { <column_name> | <column_expression> }
     예) CREATE INDEX EMP_NAME_INDEX ON EMP (UPPER(ENAME));
     CREATE INDEX EMP_SAL_INDEX ON EMP( SAL + COMM, empno);
     * Function-based index를 생성하기 위해서는 QUERY REWRITE 권한이
     부여 되어 있어야만 한다.
     예) GRANT QUERY REWRITE TO SCOTT;
5. Function-Based Index 사용을 위한 사전 작업
     1) Function-based index는 cost based optimizer에서만 사용 가능하므로,
     테이블에 대해 미리 analyze 해 주는 것이 바람직하다.
     그리고 init 파일에서 OPTIMIZER_MODE 를 FIRST_ROWS 나 ALL_ROWS 등으
로 지정하거나 HINT 등을 사용하여 cost based optimizer가 사용되도록
한다.
     2) init 파일에서 COMPATIBLE 파라미터 값을 8.1 이상으로 설정되어 있어야
한다.
     ( 예 : COMPATIBLE = 8.1.6 )
     3) session/instance level 에서 QUERY_REWRITE_ENABLED 값이 TRUE 지정
되어 있어야 한다.
     ( 예 : ALTER SESSION SET QUERY_REWRITE_ENABLED = TRUE; )
6. 예제
     1) init 파라미터에서 다음과 같이 지정
     compatible = 8.1.6 (반드시 8.1이상이어야 한다)
     query_rewrite_enabled = true
     query_rewrite_integrity = trusted
     2) SCOTT 유저에서 function_based_index 생성
     create index idx_emp_lower_ename
     on emp
     ( lower(ename) ) ;
     3) EMP table analyze
     analyze table emp compute statistics ;
     4) PLAN_TABLE 생성
     @ ?/rdbms/admin/utlxplan.sql
     5) Cost based optimizer 선택
     alter session set optimizer_mode = FIRST_ROWS ;
     6) Query 실행
     explain plan set statement_id='qry1' FOR
     select empno, ename
     from emp
     where lower(ename) = 'ford' ;
     7) PLAN 분석
     SELECT LPAD(' ',2*level-2)||operation||' '||options||' '||object_name query_plan
     FROM plan_table
     WHERE statement_id='qry1'
     CONNECT BY prior id = parent_id
     START WITH id = 0 order by id ;
     -> 결과
     QUERY_PLAN
     SELECT STATEMENT
     TABLE ACCESS BY INDEX ROWID EMP
     INDEX RANGE SCAN IDX_EMP_LOWER_ENAME
7. 결론
Function-based index는 적절하게 사용될 경우 성능상의 많은 이점을 가져
온다. Oracle8i Designing and Tuning for Performance에서도 가능한 한
Function-based index를 사용하는 것을 권장하고 있으며, LOWER(), UPPER()
등의 함수를 사용하여 불가피하게 FULL TABLE SCAN을 하는 경우에 대해서도
효과적으로 처리해 줄 수 있는 방안이라 할 수 있다.
Reference Documents
-------------------

Partha:
From the Oracle8i Administrators Guide:
"Table owners should have EXECUTE privileges on the functions used in function-based indexes.
For the creation of a function-based index in your own schema, you must be
granted the CREATE INDEX and QUERY REWRITE system privileges. To create
the index in another schema or on another schemas tables, you must have the
CREATE ANY INDEX and GLOBAL QUERY REWRITE privileges."
Hope this helps.
Peter

Query not considering function based index in oracle 11g

I have a query which used Function Based Index when run in oracle 9i but when I run the same query
without any changes, it does not consider index. Below is the query:
SELECT distinct patient_role.domain_key, patient_role.patient_role_key,
patient_role.emergency_contact_name,
patient_role.emergency_contact_phone, patient_role.emergency_contact_note,
patient_role.emergency_contact_relation_id,
patient_role.financial_class_desc_id, no_known_allergies, patient_role.CREATED_BY,
patient_role.CREATED_TIMESTAMP,
patient_role.CREATED_TIMESTAMP_TZ, patient_role.UPDATED_BY, patient_role.UPDATED_TIMESTAMP,
patient_role.UPDATED_TIMESTAMP_TZ,
patient_role.discontinued_date
FROM encounter, patient_role
WHERE patient_role.patient_role_key = encounter.patient_role_key
AND UPPER(TRIM(leading :SYS_B_0 from encounter.account_number)) = UPPER(TRIM(leading :SYS_B_1 from
:SYS_B_2))
AND patient_role.discontinued_date IS null
AND encounter.discontinued_date IS null ;
Index definition:
CREATE INDEX "user1"."IX_TRIM_ACCOUNT_NUMBER" ON "user1."ENCOUNTER" (UPPER(TRIM(LEADING
'0' FROM "ACCOUNT_NUMBER")), "PATIENT_ROLE_KEY", "DOMAIN_KEY", "DISCONTINUED_DATE")
PCTFREE 10 INITRANS 2 MAXTRANS 255 COMPUTE STATISTICS
STORAGE(INITIAL 65536 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645
PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1
BUFFER_POOL DEFAULT)
TABLESPACE "user1"
Database : Oracle 11g (11.2.0.3)
O/S : Linux 64 bit (the query does not consider index even on windows os)
Any suggestions?
-Onkar
Edited by: onkar.nath on Jul 2, 2012 3:32 PM

Onkar,
I don't appreciate you posting this question in several forums at the same time.
If I would know you also posted this on Asktom, I wouldn't even have bothered.
As to your 'issue':
First of all: somehow cursor_sharing MUST have been set to FORCE. Oracle is a predictable system, not a fruitmachine.
Your statement the '0' is replaced by a bind variable anyway is simply false. If you really believe it is not false, SUBMIT a SR.
But your real issue is not Oracle: it is your 'application', which is a mess anyway. Allowing for alphanumeric numbers is a really bad idea.
Right now you are already putting workaround on workaround on workaround on workaround.
Issue is the application: it is terminal., and you either need to kill it, or to replace it.
Sybrand Bakker
Senior Oracle DBA

Function Based Index on Date Column

Hi All,
I need to execute a query like this :
SELECT * FROM ORDERS WHERE APPROVE_DATE IS NULL
I read anywhere that this will cause unnecessary FTS so that I should create function based index.
I have tried one below , but not sure that this is correct approach :
CREATE INDEX idx_1
ON ORDERS (NVL(APPROVE_DATE, '01-JAN-1900'));
SELECT * FROM ORDERS WHERE NVL(APPROVE_DATE, '01-JAN-1900') = '01-JAN-1900'
Is this a correct approach ?
Thank you,
xtanto

A SQL_TRACE output will explain clearly what Justin has stated.
I have created a table T based on all_objects.
SQL> desc t
Name                                      Null?    Type
OWNER                                     NOT NULL VARCHAR2(30)
OBJECT_NAME                               NOT NULL VARCHAR2(30)
SUBOBJECT_NAME                                     VARCHAR2(30)
OBJECT_ID                                 NOT NULL NUMBER
DATA_OBJECT_ID                                     NUMBER
OBJECT_TYPE                                        VARCHAR2(19)
CREATED                                            DATE
LAST_DDL_TIME                             NOT NULL DATE
TIMESTAMP                                          VARCHAR2(19)
STATUS                                             VARCHAR2(7)
TEMPORARY                                          VARCHAR2(1)
GENERATED                                          VARCHAR2(1)
SECONDARY                                          VARCHAR2(1)
CASE I_
SQL> select count(1) from t
2 /
COUNT(1)
    934320
SQL> select count(1) from t where created is null
2 /
COUNT(1)
      2376The number of null values in CREATED column is proportionately very small.
Now i execute the query without function based index.
select *
from t
where created is null
call     count       cpu    elapsed       disk      query    current        rows
Parse        1      0.00       0.09          0          0          0           0
Execute      1      0.00       0.00          0          0          0           0
Fetch      160      0.04       0.10          0      12662          0        2376
total      162      0.04       0.19          0      12662          0        2376
Rows     Execution Plan
      0 SELECT STATEMENT   GOAL: ALL_ROWS
   2376   TABLE ACCESS   GOAL: ANALYZED (FULL) OF 'T' (TABLE)And here is the query that uses the function based index
select *
from t
where nvl(created,to_date('01-01-1900','DD-MM-YYYY')) = to_date('01-01-1900','DD-MM-YYYY')
call     count       cpu    elapsed       disk      query    current        rows
Parse        1      0.01       0.00          0          0          0           0
Execute      1      0.00       0.00          0          0          0           0
Fetch      160      0.01       0.01          0        698          0        2376
total      162      0.03       0.01          0        698          0        2376
Rows     Execution Plan
      0 SELECT STATEMENT   GOAL: ALL_ROWS
   2376   TABLE ACCESS   GOAL: ANALYZED (BY INDEX ROWID) OF 'T' (TABLE)
   2376    INDEX   GOAL: ANALYZED (RANGE SCAN) OF 'T_FN_IDX' (INDEX)Its very obvious from the above output that the Function Based Index as increased the performance.
CASE II_
SQL> select count(1) from t
2 /
COUNT(1)
    934320
SQL> select count(1) from t where created is null
2 /
COUNT(1)
    202168Now the null values in the CREATED column is proportionately large than the first test case.
Now lets see without using the function based index
select *
from t
where created is null
call     count       cpu    elapsed       disk      query    current        rows
Parse        1      0.00       0.00          0          0          0           0
Execute      1      0.00       0.00          0          0          0           0
Fetch    13479      0.46       0.71          2      25832          0      202168
total    13481      0.46       0.71          2      25832          0      202168
Rows     Execution Plan
      0 SELECT STATEMENT   GOAL: ALL_ROWS
202168   TABLE ACCESS   GOAL: ANALYZED (FULL) OF 'T' (TABLE)Now iam trying to use the function based index
select *
from t
where nvl(created,to_date('01-01-1900','DD-MM-YYYY')) = to_date('01-01-1900','DD-MM-YYYY')
call     count       cpu    elapsed       disk      query    current        rows
Parse        1      0.00       0.00          0          0          0           0
Execute      1      0.00       0.00          0          0          0           0
Fetch    13479      0.54       0.84          0      33826          0      202168
total    13481      0.54       0.84          0      33826          0      202168
Rows     Execution Plan
      0 SELECT STATEMENT   GOAL: ALL_ROWS
202168   TABLE ACCESS   GOAL: ANALYZED (FULL) OF 'T' (TABLE)Its obvious from the result that oracle has decided to go for a FULL TABLE SCAN even when an index was available.
So just having a function based index is not going to increase the query performance. There are lot of other factors to be considered as stated above.
Thanks,
Karthick.

Function Based Index

Hi All,
select * from v$version;
BANNER
Oracle Database 11g Enterprise Edition Release 11.1.0.7.0 - 64bit Production
PL/SQL Release 11.1.0.7.0 - Production
CORE 11.1.0.7.0 Production
TNS for Linux: Version 11.1.0.7.0 - Production
NLSRTL Version 11.1.0.7.0 - ProductionI have a 10GB partitioned table which has INVOICE_DUE_DATE column. Table is partitioned on CREATION_DATE. All records which has CREATION_DATE less than 01-jan-2010 have INVOICE_DUE_DATE set to NULL and new records (for year 2011)are updated with recent date(i.e. sysdate) by 'due_date_update' process. Some developers want indexing on INVOICE_DUE_DATE column as they have SLA critical reports running against INVOICE_DUE_DATE column. (where INVOICE_DUE_DATE > :B1) B1 could be any date in 2011.
As of now, ~85% records are having INVOICE_DUE_DATE set to NULL.
Given above scenarios,Can i use function based index to index all rows where INVOICE_DUE_DATE is any date in 2011 ?
Edited by: OraDBA02 on Jan 11, 2011 4:00 AM

OraDBA02 wrote:
Given above scenarios,Can i use function based index to index all rows where INVOICE_DUE_DATE is any date in 2011 ?I suppose you could, but you might not need to. If you had an index that just contained the INVOICE_DUE_DATE column it wouldn't index the NULL values anyways.

Where to find info on function based indexes

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