分區就是將一個非常大的表或者索引物理地分解爲多個較小的 可獨立管理的部分.
分區表或索引在邏輯上是一個表或一個索引,但物理上是由多個物理分區組成的.
分區功能通過改善可管理性 性能 可用性,爲各種應用系統帶來了極大的好處.
分區功能的好處:
1.增強數據可用性:如果表的一個分區因故障或者維護而不能使用時,表的其餘分區仍是可用的;
2.維護方便:獨立管理多個分區,比維護單個大表要輕鬆;
3.均衡I/O:可以把不同分區映射到磁盤以平衡I/O,顯著改善性能;
4.改善查詢性能:對已分區對象的某些查詢可以運行更快,因爲搜索僅限於關心的分區;
分區表有哪些??
Oracle 11g 提供6種表分區方法:範圍分區(range) 散列分區(hash) 列表分區(list)
符合分區 間隔分區 引用分區.
<範圍分區 partition by range>
按表中某個列值的範圍進行分區,根據該列的值決定將數據存儲在哪個分區上.
創建範圍分區需注意以下幾點:
1.指明分區方法,分區列,和分區描述
2.每一個分區都有values less than子句
3.在最高分區中定義maxvalue,這個maxvalue值高區其他分區中的任何鍵值.
例:創建範圍分區
create table range_orders
(order_id varchar2(10) constraint OR_PK primary key
,order_date date default sysdate
,qty integer
,payterms varchar2(10)
,book_id number(6)
)
partition by range (order_date)
(partition p1 values less than (to_date('20140331','yyyymmdd')) tablespace user01,
partition p2 values less than (to_date('20140430','yyyymmdd')) tablespace user02,
partition p3 values less than (to_date('20140531','yyyymmdd')) tablespace user03
)
;
SQL> insert into range_orders values ('10001',to_date('20140321','yyyymmdd'),1,'payterm_1',110345);
1 row inserted
SQL> insert into range_orders values ('10002',to_date('20140421','yyyymmdd'),1,'payterm_2',110745);
1 row inserted
SQL> insert into range_orders values ('10003',to_date('20140521','yyyymmdd'),1,'payterm_3',110945);
1 row inserted
SQL> commit;
Commit complete
SQL> select rowid,r.* from range_orders r;
ROWID ORDER_ID ORDER_DATE QTY PAYTERMS BOOK_ID
------------------ ---------- ----------- ---- ---------- -------
AAADwpAAGAAAACFAAA 10001 2014/3/21 1 payterm_1 110345
AAADwqAAHAAAACFAAA 10002 2014/4/21 1 payterm_2 110745
AAADwrAAIAAAACFAAA 10003 2014/5/21 1 payterm_3 110945
可以看到AAG,AAH,AAI 分別代表了三條數據的文件號是6,7,8備註:這個地方可以看下http://blog.itpub.net/28929558/viewspace-1150766/ 瞭解rowid
驗證下
SQL> select x.FILE#,x.NAME from v$datafile x;
FILE# NAME
---------- ----------------------------------------
1 D:\ORACLE\ORADATA\CRISS_DB\SYSTEM01.DBF
2 D:\ORACLE\ORADATA\CRISS_DB\SYSAUX01.DBF
3 D:\ORACLE\ORADATA\CRISS_DB\UNDOTBS01.DBF
4 D:\ORACLE\ORADATA\CRISS_DB\USERS01.DBF
5 D:\ORACLE\ORADATA\CRISS_DB\TEST01.DBF
6 D:\ORACLE\ORADATA\CRISS_DB\USER01.DBF
7 D:\ORACLE\ORADATA\CRISS_DB\USER02.DBF
8 D:\ORACLE\ORADATA\CRISS_DB\USER03.DBF
8 rows selected
<散列分區 partition by hash>散列分區指一個或多個列上應用一個散列函數,數根據該散列值存放在不同的分區中.
通過散列分區,可以將數據比較均勻地分佈到各個分區中.
例:創建散列分區表
SQL> create table hash_orders
(order_id varchar2(10) constraint HOR_PK primary key
,order_date date default sysdate
,qty integer
,payterms varchar2(10)
,book_id number(6)
)
partition by hash(order_id)
( partition hash_p1 tablespace user01
,partition hash_p2 tablespace user02
);
Table created
SQL> insert into hash_orders select * from range_orders;
3 rows inserted
SQL> select rowid,h.* from hash_orders h;
ROWID ORDER_ID ORDER_DATE QTY PAYTERMS BOOK_ID
------------------ ---------- ----------------- ---------- -------
AAADyIAAGAAAACNAAA 10002 2014/4/21 1 payterm_2 110745
AAADyIAAGAAAACNAAB 10003 2014/5/21 1 payterm_3 110945
AAADyJAAHAAAACNAAA 10001 2014/3/21 1 payterm_1 110345
order_id爲 10002,10003的被存在AAG 6號文件上,第141個塊上的 第1行和第2行10001 存放在AAH 7號文件上
<列表分區 partition by list>
當表中某列的值只有幾個的時候,可以採用列表分區,即指定在幾個(根據列值個數)表空間中.
SQL> create table list_orders
(order_id varchar2(10) constraint LOR_PK primary key
,order_date date default sysdate
,qty integer
,payterms varchar2(10)
,book_id number(6)
)
partition by list(payterms)
( partition list_p1 values('payterm_1') tablespace user01
,partition list_p2 values('payterm_2')tablespace user02
,partition list_p3 values('payterm_3') tablespace user03
);
Table created
SQL> select rowid,l.* from list_orders l;
ROWID ORDER_ID ORDER_DATE QTY PAYTERMS BOOK_ID
------------------ ---------- ------------------ ---------- -------
AAADyRAAGAAAACdAAA 10001 2014/3/21 1 payterm_1 110345
AAADySAAHAAAACdAAA 10002 2014/4/21 1 payterm_2 110745
AAADyTAAIAAAACVAAA 10003 2014/5/21 1 payterm_3 110945
<複合分區>基於範圍分區和列表分區的組合 或 範圍分區和散列分區的組合
SQL> create table comp_orders
(order_id varchar2(10) constraint COR_PK primary key
,order_date date default sysdate
,qty integer
,payterms varchar2(10)
,book_id number(6)
)
partition by range (order_date)
subpartition by list(payterms)
(partition p1 values less than (to_date('20140331','yyyymmdd'))
( subpartition p1_sub1 values('payterm_1') tablespace user01
,subpartition p1_sub2 values('payterm_2') tablespace user02
,subpartition p1_sub3 values('payterm_3') tablespace user03
)
,partition p2 values less than (to_date('20140430','yyyymmdd'))
( subpartition p2_sub1 values('payterm_1') tablespace user04
,subpartition p2_sub2 values('payterm_2') tablespace user05
,subpartition p2_sub3 values('payterm_3') tablespace user06
)
,partition p3 values less than (maxvalue) tablespace user07
)
;
Table created
SQL> select rowid,c.* from comp_orders c;
ROWID ORDER_ID ORDER_DATE QTY PAYTERMS BOOK_ID
------------------ ---------- ----------- ----- ---------- -------
AAADyZAAGAAAAClAAA 10004 2014/3/21 1 payterm_1 110345
AAADyZAAGAAAAClAAB 10001 2014/3/21 1 payterm_1 110345
AAADydAAKAAAACFAAA 10005 2014/4/21 1 payterm_2 110745
AAADydAAKAAAACFAAB 10002 2014/4/21 1 payterm_2 110745
AAADyfAAMAAAACFAAA 10006 2014/5/21 1 payterm_3 110945
AAADyfAAMAAAACFAAB 10003 2014/5/21 1 payterm_3 110945
6 rows selected
PAYTERMS字段值相同,且ORDER_DATE時間區間相同的數據被放到同一個表空間下面.下面對比下PAYTERMS字段值相同,ORDER_DATE時間區間不同的結果
SQL> insert into comp_orders values('10007',to_date('20140421','yyyymmdd'),1,'payterm_1','113888');
1 row inserted
SQL> select rowid,c.* from comp_orders c;
ROWID ORDER_ID ORDER_DATE QTY PAYTERMS BOOK_ID
------------------ ---------- ---------------- ---------- -------
AAADyZAAGAAAAClAAA 10004 2014/3/21 1 payterm_1 110345
AAADyZAAGAAAAClAAB 10001 2014/3/21 1 payterm_1 110345
AAADycAAJAAAACFAAA 10007 2014/4/21 1 payterm_1 113888
AAADydAAKAAAACFAAA 10005 2014/4/21 1 payterm_2 110745
AAADydAAKAAAACFAAB 10002 2014/4/21 1 payterm_2 110745
AAADyfAAMAAAACFAAA 10006 2014/5/21 1 payterm_3 110945
AAADyfAAMAAAACFAAB 10003 2014/5/21 1 payterm_3 110945
7 rows selected
ORDER_ID爲10007的數據存放在了另一個表空間內(AAJ AAADyc[AAJ]AAAACFAAA)
<間隔分區>
間隔分區是oracle 11g release 1 以後版本中新增的特性,它是對範圍分區的擴展,
可以自動進行等距離範圍的分區.
實驗對比一下,間隔分區與範圍分區有什麼區別即可.
首先創建一個間隔分區,間隔分區以一個範圍分區爲'起點',並定義一個間隔,
當有數據插入,依據該間隔爲附加的數據創建新的分區.
SQL> create table intvl_orders
(order_id varchar2(10) constraint INO_PK primary key
,order_date date default sysdate
,qty integer
,payterms varchar2(10)
,book_id number(6)
)
partition by range (order_date)
interval(numtoyminterval(1,'MONTH'))
store in (user01,user02,user03)
(
partition p1 values less than (to_date('20140101','yyyymmdd'))
)
;
Table created
注意:partition p1 values less than (to_date('20140101','yyyymmdd')) 起始是月初,不然會報錯 ORA-14767: 無法使用現有上限指定此間隔.至於爲什麼,大家自行去查找下答案吧.
重新創建一個範圍分區表並插入數據!
SQL> drop table range_orders purge;
Table dropped
SQL>
SQL> create table range_orders
(order_id varchar2(10) constraint OR_PK primary key
,order_date date default sysdate
,qty integer
,payterms varchar2(10)
,book_id number(6)
)
partition by range (order_date)
(partition p1 values less than (to_date('20140331','yyyymmdd')) tablespace user01,
partition p2 values less than (to_date('20140430','yyyymmdd')) tablespace user02,
partition p3 values less than (to_date('20140531','yyyymmdd')) tablespace user03
)
;
Table created
SQL> insert into range_orders values ('10003',to_date('20140621','yyyymmdd'),1,'payterm_3',110945);
insert into range_orders values ('10003',to_date('20140621','yyyymmdd'),1,'payterm_3',110945)
ORA-14400: 插入的分區關鍵字未映射到任何分區
SQL> insert into range_orders values ('10003',to_date('20140521','yyyymmdd'),1,'payterm_3',110945);
1 row inserted
可以看到,新創建的範圍分區表最大範圍是20140531,當出入的數據超出分區範圍就會報錯,需要手工去做分區擴展.下面再給間隔分區插入數據
SQL> insert into intvl_orders values ('10003',to_date('20140621','yyyymmdd'),1,'payterm_3',110945);
1 row inserted
我們插入同樣超出分區範圍的數據,數據插入成功了!我們看一下前後兩次的建表語句有什麼變化
剛剛建好間隔分區表時候oracle內的建表語句:
-- Create table
create table INTVL_ORDERS
(
ORDER_ID VARCHAR2(10) not null,
ORDER_DATE DATE default sysdate,
QTY INTEGER,
PAYTERMS VARCHAR2(10),
BOOK_ID NUMBER(6)
)
partition by range (ORDER_DATE)
(
partition P1 values less than (TO_DATE(' 2014-01-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIAN'))
tablespace USERS
pctfree 10
initrans 1
maxtrans 255
storage
(
initial 64K
next 1M
minextents 1
maxextents unlimited
)
);
-- Create/Recreate primary, unique and foreign key constraints
alter table INTVL_ORDERS
add constraint INO_PK primary key (ORDER_ID)
using index
tablespace USERS
pctfree 10
initrans 2
maxtrans 255
storage
(
initial 64K
next 1M
minextents 1
maxextents unlimited
);
插入數據後間隔分區表時候oracle內的建表語句:
-- Create table
create table INTVL_ORDERS
(
ORDER_ID VARCHAR2(10) not null,
ORDER_DATE DATE default sysdate,
QTY INTEGER,
PAYTERMS VARCHAR2(10),
BOOK_ID NUMBER(6)
)
partition by range (ORDER_DATE)
(
partition P1 values less than (TO_DATE(' 2014-01-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIAN'))
tablespace USERS
pctfree 10
initrans 1
maxtrans 255
storage
(
initial 64K
next 1M
minextents 1
maxextents unlimited
),
partition SYS_P22 values less than (TO_DATE(' 2014-07-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIAN'))
tablespace USER01
pctfree 10
initrans 1
maxtrans 255
storage
(
initial 64K
next 1M
minextents 1
maxextents unlimited
)
);
-- Create/Recreate primary, unique and foreign key constraints
alter table INTVL_ORDERS
add constraint INO_PK primary key (ORDER_ID)
using index
tablespace USERS
pctfree 10
initrans 2
maxtrans 255
storage
(
initial 64K
next 1M
minextents 1
maxextents unlimited
);
結果自動擴展了一個分區!這也就是間隔分區的特點.間隔分區會根據起始區間和一個間隔(之前我們設置的是一個月),插入數據時,
會創建相應的分區,而不會因數據超出分區範圍導致語句執行失敗.
<引用分區>
引用分區通過父表繼承分區鍵,可以在邏輯上均分具有分子關係的表.
分區鍵通過現有的父子關係解析,由現行的主鍵或外鍵約束實施.
SQL> create table range_books
(bookid number(6) primary key
,bookname varchar2(40) not null
,booktime date default sysdate
)
partition by range(booktime)
(
partition p1 values less than (to_date('20140331','yyyymmdd'))
,partition p2 values less than (to_date('20140430','yyyymmdd'))
);
Table created
SQL> create table ref_order
(order_id varchar2(20) constraint RFO_PK primary key
,order_date date default sysdate
,book_id number(6) not null--not null !!!
,constraint RFO_FK foreign key (book_id) references range_books(bookid)
)
partition by reference (RFO_FK)
;
Table created
上面的實驗,通過使用外鍵發現分區機制,外鍵[RFO_FK]指向父表'range_books',因此,子表'ref_order'就按照父表的分區方式進行相應的分區.
注意:創建引用分區表時,通過[partition by reference]子句指定分區方法,
其後括號中指定分區使用的約束.外鍵約束引用的列必須具有not null約束.
=========================================================================
分區表維護:
主要的就是 刪除分區 | 增加分區 | 合併分區 | 移動分區 | 重命名 | 截斷分區
刪除分區:
alter table range_orders drop partition p2;
增加分區:
alter table range_orders add partition p2 values
less than (to_date('20140430','yyyymmdd')) tablespace user02;
合併分區:
alter table range_orders merge partition p1,p2 into partition p2;
移動分區:
alter table range_orders move partition p2 tablespace user05;
重命名:
alter table range_orders rename partition p2 to p1;
截斷分區:
alter table range_orders truncate partition p1;