ASP.NET Web PDF Document Viewer/Editor Control Library

To make the retrieval more efficient, you can use an IOT for the child table to put all of the records for a given employee near each other upon insertion, so when you retrieve them over and over again, you do less work An example will easily show the effects of using an IOT to physically co-locate the child table information Let s create and populate an EMP table: ops$tkyte%ORA11GR2> create table emp 2 as 3 select object_id empno, 4 object_name ename, 5 created hiredate, 6 owner job 7 from all_objects 8 / Table created ops$tkyte%ORA11GR2> alter table emp add constraint emp_pk primary key(empno) 2 / Table altered ops$tkyte%ORA11GR2> begin 2 dbms_statsgather_table_stats( user, 'EMP', cascade=>true ); 3 end; 4 / PL/SQL procedure successfully completed.

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Next, we ll implement the child table two times, once as a conventional heap table and again as an IOT: ops$tkyte%ORA11GR2> create table heap_addresses 2 ( empno references emp(empno) on delete cascade, 3 addr_type varchar2(10), 4 street varchar2(20), 5 city varchar2(20), 6 state varchar2(2), 7 zip number,.

Since the F# compiler targets the CLR, its output will be managed code, allowing compiled programs to interact directly with other programming languages targeting the .NET platform. We already showed how to exploit this form of interoperability in 10, when we showed how to develop a graphic control in F# and use it in a C# application.

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primary key (empno,addr_type) ) /

Interoperability of F# programs with unmanaged code requires an understanding of the structure of the most important elements of a programming language s runtime. In particular, you must consider how program memory is organized at run time. Memory used by a program is generally classified in three classes depending on the way it is handled: Static memory, allocated for the entire lifetime of the program Automatic memory, allocated and freed automatically when functions or methods are executed Dynamic memory, explicitly allocated by the program and freed explicitly or by an automatic program called the garbage collector As a rule of thumb, top-level variables and static fields belong to the first class, function arguments and local variables belong to the second class, and memory explicitly allocated using the new operator belongs to the last class. The code generated by the JIT compiler uses different data structures to manage memory and automatically interacts with the operating system to request and release memory during program execution. Each execution thread has a stack where local variables and arguments are allocated when a function or method is invoked (see Figure 17-2). A stack is used because it naturally follows the execution flow of method and function calls. The topmost record contains data about the currently executing function; below that is the record of the caller of the function, which sits on top of another record of its caller, and so on. These activation records are memory blocks used to hold the memory required during the execution of the function and are naturally freed at the

Table created. ops$tkyte%ORA11GR2> create table iot_addresses 2 ( empno references emp(empno) on delete cascade, 3 addr_type varchar2(10), 4 street varchar2(20), 5 city varchar2(20), 6 state varchar2(2), 7 zip number, 8 primary key (empno,addr_type) 9 ) 10 ORGANIZATION INDEX 11 / Table created. I populated these tables by inserting into them a work address for each employee, then a home address, then a previous address, and finally a school address. A heap table would tend to place the data at the end of the table; as the data arrives, the heap table would simply add it to the end, due to the fact that the data is just arriving and no data is being deleted. Over time, if addresses are deleted, the inserts would become more random throughout the table. Suffice it to say, the chance an employee s work address would be on the same block as his home address in the heap table is near zero. For the IOT, however, since the key is on EMPNO, ADDR_TYPE, we ll be pretty sure that all of the addresses for a given EMPNO are located on one or maybe two index blocks together. The inserts used to populate this data were: ops$tkyte%ORA11GR2> insert into heap_addresses 2 select empno, 'WORK', '123 main street', 'Washington', 'DC', 20123 3 from emp; 72075 rows created. ops$tkyte%ORA11GR2> insert into iot_addresses 2 select empno, 'WORK', '123 main street', 'Washington', 'DC', 20123 3 from emp; 72075 rows created. I did that three more times, changing WORK to HOME, PREV, and SCHOOL in turn. Then I gathered statistics: ops$tkyte%ORA11GR2> exec dbms_stats.gather_table_stats( user, 'HEAP_ADDRESSES' ); PL/SQL procedure successfully completed. ops$tkyte%ORA11GR2> exec dbms_stats.gather_table_stats( user, 'IOT_ADDRESSES' ); PL/SQL procedure successfully completed.