TimesTen 应用层数据库缓存学习：9. 一些独特的缓存组定义选项

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在缓存组定义中，有一些选项，它们平常很少会用到，但在一些特定的场合也许有用。
这些选项是：
* ON DELETE CASCADE
* UNIQUE HASH ON
* Where 条件中的SYNONYM
* 缓存LOB数据

ON DELETE CASCADE

on delete cascade由于涉及到delete操作，因此一般用于AWT缓存组。不过只读缓存组也可以用。

设定了ON DELETE CASCADE的只读缓存组

对于只读缓存组，在Oracle端可以不指定on delete cascade，而且可以没有主外键约束。在Oracle端删除root table的数据时，通过autorefresh反馈到timesten端，然后timesten执行on delete cascade。

CREATE TABLE customer
(cust_num NUMBER(6) NOT NULL PRIMARY KEY,
region VARCHAR2(10),
name VARCHAR2(50),
address VARCHAR2(100));
CREATE TABLE orders
(ord_num NUMBER(10) NOT NULL PRIMARY KEY,
cust_num NUMBER(6) NOT NULL,
when_placed DATE NOT NULL,
when_shipped DATE NOT NULL);insert into customer values ( 1, 'West', 'Frank Edwards', '100 Pine St. Portland OR' );
insert into customer values ( 2, 'East', 'Angela Wilkins', '356 Olive St. Boston MA' );
insert into customer values ( 3, 'Midwest', 'Stephen Johnson', '7638 Walker Dr. Chicago IL' );
INSERT INTO customer VALUES (4, 'East', 'Roberta Simon', '3667 Park Ave. New York NY');INSERT INTO orders VALUES(1,1, DATE '2012-01-25', DATE '2012-01-30');
commit;cacheadm> 
CREATE READONLY CACHE GROUP customer_orders
FROM tthr.customer
(cust_num NUMBER(6) NOT NULL,
region VARCHAR2(10),
name VARCHAR2(50),
address VARCHAR2(100),
PRIMARY KEY(cust_num)),
tthr.orders
(ord_num NUMBER(10) NOT NULL,
cust_num NUMBER(6) NOT NULL,
when_placed DATE NOT NULL,
when_shipped DATE NOT NULL,
PRIMARY KEY(ord_num),
FOREIGN KEY(cust_num) REFERENCES tthr.customer(cust_num) ON DELETE CASCADE);cacheadm>load cache group customer_orders commit every 256 rows;
4 cache instances affected.
tthr>select * from customer;
< 1, West, Frank Edwards, 100 Pine St. Portland OR >
< 2, East, Angela Wilkins, 356 Olive St. Boston MA >
< 3, Midwest, Stephen Johnson, 7638 Walker Dr. Chicago IL >
< 4, East, Roberta Simon, 3667 Park Ave. New York NY >
4 rows found.
tthr>select * from orders;
< 1, 1, 2012-01-25 00:00:00, 2012-01-30 00:00:00 >
1 row found.
SQL> delete from customer where cust_num = 1;1 row deleted.SQL> commit;Commit complete.SQL> select * from orders;ORD_NUM   CUST_NUM WHEN_PLAC WHEN_SHIP
---------- ---------- --------- ---------1          1 25-JAN-12 30-JAN-125分钟后，autorefresh生效，着急的话可以手工refresh一次。
tthr>select * from customer;
< 2, East, Angela Wilkins, 356 Olive St. Boston MA >
< 3, Midwest, Stephen Johnson, 7638 Walker Dr. Chicago IL >
< 4, East, Roberta Simon, 3667 Park Ave. New York NY >
3 rows found.
tthr>select * from orders; <- on delete cascade生效了
0 rows found.不过此时Oracle与TimesTen的数据已经不一致了。
SQL> select * from orders;ORD_NUM   CUST_NUM WHEN_PLAC WHEN_SHIP
---------- ---------- --------- ---------1          1 25-JAN-12 30-JAN-12

设定了ON DELETE CASCADE的AWT缓存组

对于AWT缓存组，oracle端必须有匹配的主外键关系，必须指定on delete cascade。

CREATE ASYNCHRONOUS WRITETHROUGH CACHE GROUP customer_orders
FROM tthr.customer
(cust_num NUMBER(6) NOT NULL,
region VARCHAR2(10),
name VARCHAR2(50),
address VARCHAR2(100),
PRIMARY KEY(cust_num)),
tthr.orders
(ord_num NUMBER(10) NOT NULL,
cust_num NUMBER(6) NOT NULL,
when_placed DATE NOT NULL,
when_shipped DATE NOT NULL,
PRIMARY KEY(ord_num),
FOREIGN KEY(cust_num) REFERENCES tthr.customer(cust_num) ON DELETE CASCADE);
cacheadm>CREATE ASYNCHRONOUS WRITETHROUGH CACHE GROUP customer_orders> FROM tthr.customer> (cust_num NUMBER(6) NOT NULL,> region VARCHAR2(10),> name VARCHAR2(50),> address VARCHAR2(100),> PRIMARY KEY(cust_num)),> tthr.orders> (ord_num NUMBER(10) NOT NULL,> cust_num NUMBER(6) NOT NULL,> when_placed DATE NOT NULL,> when_shipped DATE NOT NULL,> PRIMARY KEY(ord_num),> FOREIGN KEY(cust_num) REFERENCES tthr.customer(cust_num) ON DELETE CASCADE);5164: No matching foreign key with cascade action for table TTHR.ORDERS on Oracle
The command failed.
SQL>
CREATE TABLE customer
(cust_num NUMBER(6) NOT NULL PRIMARY KEY,
region VARCHAR2(10),
name VARCHAR2(50),
address VARCHAR2(100));
CREATE TABLE orders
(ord_num NUMBER(10) NOT NULL PRIMARY KEY,
cust_num NUMBER(6) NOT NULL,
when_placed DATE NOT NULL,
when_shipped DATE NOT NULL,
FOREIGN KEY(cust_num) REFERENCES customer(cust_num));
insert into customer values ( 1, 'West', 'Frank Edwards', '100 Pine St. Portland OR' );
insert into customer values ( 2, 'East', 'Angela Wilkins', '356 Olive St. Boston MA' );
insert into customer values ( 3, 'Midwest', 'Stephen Johnson', '7638 Walker Dr. Chicago IL' );
INSERT INTO customer VALUES (4, 'East', 'Roberta Simon', '3667 Park Ave. New York NY');INSERT INTO orders VALUES(1,1, DATE '2012-01-25', DATE '2012-01-30');
commit;
cacheadm>
CREATE ASYNCHRONOUS WRITETHROUGH CACHE GROUP "CUSTOMER_ORDERS" FROM"TTHR"."CUSTOMER" ("CUST_NUM" NUMBER(6)          NOT NULL,"REGION"   VARCHAR2(10 BYTE) ,"NAME"     VARCHAR2(50 BYTE) ,"ADDRESS"  VARCHAR2(100 BYTE),PRIMARY KEY("CUST_NUM")),"TTHR"."ORDERS" ("ORD_NUM"      NUMBER(10) NOT NULL,"CUST_NUM"     NUMBER(6)  NOT NULL,"WHEN_PLACED"  DATE       NOT NULL,"WHEN_SHIPPED" DATE       NOT NULL,PRIMARY KEY("ORD_NUM"),FOREIGN KEY("CUST_NUM")REFERENCES "TTHR"."CUSTOMER"("CUST_NUM")ON DELETE CASCADE);5164: No matching foreign key with cascade action for table TTHR.ORDERS on Oracle
The command failed.
CREATE TABLE customer
(cust_num NUMBER(6) NOT NULL PRIMARY KEY,
region VARCHAR2(10),
name VARCHAR2(50),
address VARCHAR2(100));
CREATE TABLE orders
(ord_num NUMBER(10) NOT NULL PRIMARY KEY,
cust_num NUMBER(6) NOT NULL,
when_placed DATE NOT NULL,
when_shipped DATE NOT NULL,
FOREIGN KEY(cust_num) REFERENCES customer(cust_num) ON DELETE CASCADE);
cacheadm>
CREATE ASYNCHRONOUS WRITETHROUGH CACHE GROUP "CUSTOMER_ORDERS" FROM"TTHR"."CUSTOMER" ("CUST_NUM" NUMBER(6)          NOT NULL,"REGION"   VARCHAR2(10 BYTE) ,"NAME"     VARCHAR2(50 BYTE) ,"ADDRESS"  VARCHAR2(100 BYTE),PRIMARY KEY("CUST_NUM")),"TTHR"."ORDERS" ("ORD_NUM"      NUMBER(10) NOT NULL,"CUST_NUM"     NUMBER(6)  NOT NULL,"WHEN_PLACED"  DATE       NOT NULL,"WHEN_SHIPPED" DATE       NOT NULL,PRIMARY KEY("ORD_NUM"),FOREIGN KEY("CUST_NUM")REFERENCES "TTHR"."CUSTOMER"("CUST_NUM")ON DELETE CASCADE);5188: An oracle index is required on foreign key TTHR.ORDERS(CUST_NUM).
The command failed.SQL> create index idx1 on orders(cust_num);Index created.
CREATE ASYNCHRONOUS WRITETHROUGH CACHE GROUP "CUSTOMER_ORDERS" FROM"TTHR"."CUSTOMER" ("CUST_NUM" NUMBER(6)          NOT NULL,"REGION"   VARCHAR2(10 BYTE) ,"NAME"     VARCHAR2(50 BYTE) ,"ADDRESS"  VARCHAR2(100 BYTE),PRIMARY KEY("CUST_NUM")),"TTHR"."ORDERS" ("ORD_NUM"      NUMBER(10) NOT NULL,"CUST_NUM"     NUMBER(6)  NOT NULL,"WHEN_PLACED"  DATE       NOT NULL,"WHEN_SHIPPED" DATE       NOT NULL,PRIMARY KEY("ORD_NUM"),FOREIGN KEY("CUST_NUM")REFERENCES "TTHR"."CUSTOMER"("CUST_NUM")ON DELETE CASCADE);
成功！cacheadm>load cache group customer_orders commit every 256 rows;
4 cache instances affected.tthr>select * from customer;
< 1, West, Frank Edwards, 100 Pine St. Portland OR >
< 2, East, Angela Wilkins, 356 Olive St. Boston MA >
< 3, Midwest, Stephen Johnson, 7638 Walker Dr. Chicago IL >
< 4, East, Roberta Simon, 3667 Park Ave. New York NY >
4 rows found.tthr>delete from customer where cust_num = 1;
1 row deleted.
tthr>select * from orders;
0 rows found.SQL> select * from orders;no rows selectedSQL> select count(*) from customer;COUNT(*)
----------3

UNIQUE HASH ON

unique hash on 和索引相关

UNIQUE HASH ON specifies that a hash index rather than a range index is created on the primary key columns of the cache table.

TimesTen缺省的索引为range index，比较适合范围查询，而hash index适合于完全匹配查询。
是否使用unique hasn on取决于你的业务行为，即使用哪种查询更频繁些。

Referencing Oracle Database PL/SQL functions in a WHERE clause

TimesTen的缓存组操作不能直接调用Oracle中的函数，但可以通过Synonym间接调用。

A user-defined PL/SQL function in the Oracle database can be invoked indirectly in a WHERE clause within a CREATE CACHE GROUP, LOAD CACHE GROUP, or REFRESH CACHE GROUP (for dynamic cache groups only) statement.

由于函数和Synonym都是定义在Oracle端，因此最常用于只读缓存组，以及AWT缓存组的带where条件的Load和Refresh操作。

SQL>
CREATE OR REPLACE FUNCTION get_customer_name
(c_num customer.cust_num%TYPE) RETURN VARCHAR2 IS
c_name customer.name%TYPE;
BEGIN
SELECT name INTO c_name FROM customer WHERE cust_num = c_num;
RETURN c_name;
END get_customer_name;
/
GRANT EXECUTE ON get_customer_name TO PUBLIC;cacheadm>
CREATE READONLY CACHE GROUP top_customer
FROM tthr.customer
(cust_num NUMBER(6) NOT NULL,
region VARCHAR2(10),
name VARCHAR2(50),
address VARCHAR2(100),
PRIMARY KEY(cust_num))
WHERE name = get_customer_name(100);5221: Oracle syntax error in OCIStmtExecute(): ORA-00904: "GET_CUSTOMER_NAME": invalid identifier rc = -15117: Illegal WHERE clause for cache table TTHR.CUSTOMER
The command failed. <- 不能直接调用Oracle函数SQL> CREATE PUBLIC SYNONYM retname FOR get_customer_name;Synonym created.
cacheadm>
CREATE READONLY CACHE GROUP top_customer
FROM tthr.customer
(cust_num NUMBER(6) NOT NULL,
region VARCHAR2(10),
name VARCHAR2(50),
address VARCHAR2(100),
PRIMARY KEY(cust_num))
WHERE name = retname(100); <- 通过Synonym调用函数成功cacheadm>cachegroups;Cache Group CACHEADM.TOP_CUSTOMER:Cache Group Type: Read OnlyAutorefresh: YesAutorefresh Mode: IncrementalAutorefresh State: PausedAutorefresh Interval: 5 MinutesAutorefresh Status: okAging: No aging definedRoot Table: TTHR.CUSTOMERWhere Clause: name = retname(100)Table Type: Read Only1 cache group found.CREATE ASYNCHRONOUS WRITETHROUGH CACHE GROUP top_customer
FROM tthr.customer
(cust_num NUMBER(6) NOT NULL,
region VARCHAR2(10),
name VARCHAR2(50),
address VARCHAR2(100),
PRIMARY KEY(cust_num))
WHERE name = retname(100);cacheadm>CREATE ASYNCHRONOUS WRITETHROUGH CACHE GROUP top_customer> FROM tthr.customer> (cust_num NUMBER(6) NOT NULL,> region VARCHAR2(10),> name VARCHAR2(50),> address VARCHAR2(100),> PRIMARY KEY(cust_num))> WHERE name = retname(100);8268: Asynchronous or Synchronous Writethrough cache group cannot have a WHERE clause
The command failed. <-读写缓存组不允许带where条件，但可以在load/refresh时带where条件。CREATE ASYNCHRONOUS WRITETHROUGH CACHE GROUP "CUSTOMER_ORDERS" FROM"TTHR"."CUSTOMER" ("CUST_NUM" NUMBER(6)          NOT NULL,"REGION"   VARCHAR2(10 BYTE) ,"NAME"     VARCHAR2(50 BYTE) ,"ADDRESS"  VARCHAR2(100 BYTE),PRIMARY KEY("CUST_NUM")),"TTHR"."ORDERS" ("ORD_NUM"      NUMBER(10) NOT NULL,"CUST_NUM"     NUMBER(6)  NOT NULL,"WHEN_PLACED"  DATE       NOT NULL,"WHEN_SHIPPED" DATE       NOT NULL,PRIMARY KEY("ORD_NUM"),FOREIGN KEY("CUST_NUM")REFERENCES "TTHR"."CUSTOMER"("CUST_NUM"));cacheadm>load cache group customer_orders where customer.name = retname(100) commit every 256 rows;
0 cache instances affected. <-load时调用Synonym成功

缓存LOB数据

SQL>
CREATE TABLE t (
i INT NOT NULL PRIMARY KEY
, c CLOB
, b BLOB
, nc NCLOB);INSERT INTO t VALUES (1
, RPAD('abcdefg8', 2048, 'abcdefg8')
, HEXTORAW(RPAD('123456789ABCDEF8', 4000, '123456789ABCDEF8'))
, RPAD('abcdefg8', 2048, 'abcdefg8')
);
commit;grant select on t to cacheadm;
grant delete, update, insert on t to cacheadm;cacheadm>
CREATE DYNAMIC ASYNCHRONOUS WRITETHROUGH CACHE GROUP cg1
FROM tthr.t
(i INT NOT NULL PRIMARY KEY
, c CLOB
, b BLOB
, nc NCLOB);5115: Unsupported type mapping for column
<-按照user guide中的做法是错的，是文档bug，改为以下通过CREATE DYNAMIC ASYNCHRONOUS WRITETHROUGH CACHE GROUP cg1
FROM tthr.t
(i INT NOT NULL PRIMARY KEY
, c VARCHAR2(128)
, b VARBINARY(128)
, nc NVARCHAR2(128)); 

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