ITPub博客

首页 > 数据库 > Oracle > Oracle Index Organized Tables (IOT)

Oracle Index Organized Tables (IOT)

原创 Oracle 作者:mfm088 时间:2006-12-20 21:09:58 0 删除 编辑
General
Note: Index Organized Tables are tables that, unlike heap tables, are organized like B*Tree indexes.
[@more@]
Oracle Index Organized Tables (IOT)
Version 10.2
General
Note: Index Organized Tables are tables that, unlike heap tables, are organized like B*Tree indexes.
Note: From Jonathan Lewis on secondary indexes

I think secondary indexes on IOTs need some careful testing. It's probably not an area that many people have used in a high-stress environment. There are two main issues:
  • The primary key is used in the secondary index instead of a rowid so for large primary keys, the index would be bigger than the equivalent index on a simple table.
  • The secondary index holds a 'guess' block address for the row it points to so that a query can go to the right block more cheaply. But if the row has moved (e.g. leaf block split) then the guess is wrong and is a cost, not a benefit. But this won't be a problem if your application is always adding data at the 'right-hand' edge of the index.

Depending of version, there are various features and limitations on what you can do with secondary indexes that you will have to trade, balance and test, if you go down that path.

(And yes, the key compression could well have a very similar benefit to the varray idea, whilst avoiding the overhead of 'object unpickling')

Data Dictionary Objects
dba_tablesall_tablesuser_tables
dba_tab_columnsall_tab_columnsuser_tab_columns
Create
Simple Create IOT CREATE TABLE (
,
,
CONSTRAINT
PRIMARY KEY ())
ORGANIZATION INDEX;
CREATE TABLE LABOR_HOUR (
WORK_DATE DATE,
EMPLOYEE_NO VARCHAR2(8),
CONSTRAINT pk_labor_hour
PRIMARY KEY (work_date, employee_no))
ORGANIZATION INDEX;

SELECT table_name, iot_name, iot_type
FROM user_all_tables;
Index Compressed IOTCREATE TABLE (
,
,
CONSTRAINT
PRIMARY KEY ())
ORGANIZATION INDEX
COMPRESS ;
CREATE TABLE compressed_iot
(owner, object_type, object_name,
CONSTRAINT pk_compressed_iot
PRIMARY KEY(owner, object_type, object_name))
ORGANIZATION INDEX
COMPRESS 2 AS
SELECT owner, object_type, object_name
FROM all_objects;
Complex IOT with Including ClauseCREATE TABLE (
,
,
CONSTRAINT
PRIMARY KEY ())
ORGANIZATION INDEX
INCLUDING
OVERFLOW TABLESPACE ;
CREATE TABLE labor_hour (
WORK_DATE DATE,
EMPLOYEE_NO VARCHAR2(8),
SUMMIT_WORK_ORDER_NO VARCHAR2(7),
DASH VARCHAR2(2),
CLASS_CODE VARCHAR2(6),
PAYCODE VARCHAR2(2),
ASSIGNED_CREW_NUMBER VARCHAR2(5),
TRANSFER_CREW_NUMBER VARCHAR2(5),
REFERENCE_TYPE VARCHAR2(1),
REFERENCE_NUMBER VARCHAR2(10),
OVERTIME_CODE VARCHAR2(1),
SHIFT_DIFFERENTIAL VARCHAR2(1) NOT NULL,
HOURS NUMBER(4,2) NOT NULL,
MOD_USER_ID VARCHAR2(30) DEFAULT USER,
MOD_USER_DATE DATE DEFAULT SYSDATE,
CONSTRAINT pk_labor_hour
PRIMARY KEY (work_date, employee_no, summit_work_order_no, dash, class_code, paycode, assigned_crew_number, transfer_crew_number, reference_type, reference_number, overtime_code, shift_differential))
ORGANIZATION INDEX

INCLUDING hours
OVERFLOW TABLESPACE uw_data
;
Complex IOT with Including Clause And PartitioningCREATE TABLE (
,
,
CONSTRAINT
PRIMARY KEY ())
ORGANIZATION INDEX
INCLUDING
OVERFLOW TABLESPACE
PARTITION BY RANGE ()
();
CREATE TABLE labor_hour (
WORK_DATE DATE,
EMPLOYEE_NO VARCHAR2(8),
SUMMIT_WORK_ORDER_NO VARCHAR2(7),
DASH VARCHAR2(2),
CLASS_CODE VARCHAR2(6),
PAYCODE VARCHAR2(2),
ASSIGNED_CREW_NUMBER VARCHAR2(5),
TRANSFER_CREW_NUMBER VARCHAR2(5),
REFERENCE_TYPE VARCHAR2(1),
REFERENCE_NUMBER VARCHAR2(10),
OVERTIME_CODE VARCHAR2(1),
SHIFT_DIFFERENTIAL VARCHAR2(1) NOT NULL,
HOURS NUMBER(4,2) NOT NULL,
MOD_USER_ID VARCHAR2(30) DEFAULT USER,
MOD_USER_DATE DATE DEFAULT SYSDATE,
CONSTRAINT pk_labor_hour
PRIMARY KEY (work_date, employee_no, summit_work_order_no, dash, class_code, paycode, assigned_crew_number, transfer_crew_number, reference_type, reference_number, overtime_code, shift_differential))
ORGANIZATION INDEX
INCLUDING hours, mod_user_id, mod_user_date;
OVERFLOW TABLESPACE uwdata

PARTITION BY RANGE (work_date)
(PARTITION yr80 VALUES LESS THAN (TO_DATE('01-JAN-1990', 'DD-MON-YYYY')) TABLESPACE data1,
PARTITION yr90 VALUES LESS THAN (TO_DATE('01-JAN-2000', 'DD-MON-YYYY')) TABLESPACE data2,
PARTITION yr00 VALUES LESS THAN (TO_DATE('01-JAN-2001', 'DD-MON-YYYY')) TABLESPACE data3,
PARTITION yr01 VALUES LESS THAN (TO_DATE('01-JAN-2002', 'DD-MON-YYYY')) TABLESPACE data4,
PARTITION yr02 VALUES LESS THAN (TO_DATE('01-JAN-2003', 'DD-MON-YYYY')) TABLESPACE data5,
PARTITION yr03 VALUES LESS THAN (TO_DATE('01-JAN-2004', 'DD-MON-YYYY')) TABLESPACE data6,
PARTITION yr99 VALUES LESS THAN (
MAXVALUE) TABLESPACE data0);
Mapping Table Clause
Specify MAPPING TABLE to instruct Oracle to create a mapping of local to physical ROWIDs and store them in a heap-organized table. This mapping is needed in order to create a bitmap index on the index-organized table.

Oracle creates the mapping table in the same tablespace as its parent index-organized table. You cannot query, perform DML operations on, or modify the storage characteristics of the mapping table.

You cannot specify the mapping_table_clause for a partitioned index-organized table.

Create IOT with mapping table
CREATE TABLE (
,
,
CONSTRAINT (ORGANIZATION INDEX
MAPPING TABLE;
CREATE TABLE t (
x INT,
y INT,
CONSTRAINT pk_t_iot PRIMARY KEY(x))
ORGANIZATION INDEX
MAPPING TABLE;

col iot_map_table new_val iot_map

SELECT 'SYS_IOT_MAP_' || object_id iot_map_table
FROM user_objects
WHERE object_name = 'T';

desc &iot_map

-- as rows are inserted they are mapped to mapping table

column SYS_NC_01 format a20

INSERT INTO t VALUES (1, 2);
INSERT INTO t VALUES (2, 2);

SELECT rowid, a.* FROM &iot_map a;

-- on update logical row changes but mapping table row doesn't
update t set x = 3 where x = 1;

SELECT rowid, a.* FROM &iot_map a;

-- create a bitmapped index
CREATE BITMAP INDEX bix_t
ON t(y);

来自 “ ITPUB博客 ” ,链接:http://blog.itpub.net/330796/viewspace-885113/,如需转载,请注明出处,否则将追究法律责任。

请登录后发表评论 登录
全部评论

注册时间:2012-01-14

  • 博文量
    98
  • 访问量
    1025074