Distributed Database
Applications
COSC 5050
Week Five
Outline
Managing PL/SQL Code
Exceptions and Error Handling
Transaction Management
Packages
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Data Dictionary
USER_
USER_DEPENDENCIES
USER_ERRORS
USER_OBJECTS
USER_SOURCE
USER_TRIGGERS
USER_ARGUMENTS
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Data Dictionary
SELECT object_type, object_name, status
FROM user_objects
WHERE object_type IN ('PACKAGE',
'PACKAGE BODY',
'FUNCTION',
'PROCEDURE',
'TRIGGER'
)
ORDER BY object_type, status, object_name;
DESC ADD_EMPLOYEE
SELECT TEXT
FROM USER_SOURCE
WHERE NAME = 'ADD_EMPLOYEE';
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Debug PL/SQL Programs
Recompile invalid code
Source code debugger
Analyzing
Unit test
show err
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Exception Handler
System exception
An exception that is defined by Oracle and
is usually raised by the PL/SQL runtime
engine
With name or number
NO_DATA_FOUND
User defined exceptions
An exception that is defined by the
programmer and is therefore specific to the
application
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Exception
DECLARE
l_department department%ROWTYPE;
BEGIN
SELECT * INTO l_department
FROM department
WHERE dept_num = 3;
DBMS_OUTPUT.PUT_LINE(l_department.dept_name);
EXCEPTION
WHEN NO_DATA_FOUND
THEN
DBMS_OUTPUT.PUT_LINE('No data!');
WHEN TOO_MANY_ROWS
THEN
DBMS_OUTPUT.PUT_LINE('Too many rows');
END;
/
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Exception
create or replace function get_department(
ssn_in in employee.ssn%type)
return department.dept_name%type
is
l_dept_name department.dept_name%type;
begin
select dept_name into l_dept_name
from department inner join employee
on employee.dept_num = department.dept_num
where ssn = ssn_in;
dbms_output.put_line('department name: ' || l_dept_name);
return l_dept_name;
exception
when no_data_found then
dbms_output.put_line(
'no such employee or not in any department!');
return null;
end;
/
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Exception
procedure delete_department (department_id_in in number)
is
begin
delete from department where dept_num = department_id_in;
end;
procedure delete_department (department_id_in in number)
is
begin
delete from department where dept_num = department_id_in;
exception
when others then
if sqlcode = -2292 then
dbms_output.put_line
('Please delete employees for the department first.');
end if;
end;
SQLCODE is a built-in function that returns the number of
the last error raised.
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Declare Exception
Declare an exception by listing the
name of the exception followed by the
keyword EXCEPTION
invalid_company_id EXCEPTION;
Be referenced in two ways
Raise the exception:
RAISE invalid_company_id;
Handle the raised exception:
WHEN invalid_company_id THEN
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Declare Exception
procedure calc_annual_sales
(company_id_in in company.company_id%type)
is
invalid_company_id exception;
negative_balance exception;
duplicate_company boolean;
begin
… body of executable statements …
raise invalid_company_id;
exception
…
when no_data_found –- system exception
then
…
when invalid_company_id
then
…
when negative_balance
then
…
end;
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Declare Exception
procedure delete_department(department_id_in in number)
is
l_count number;
still_have_employees exception;
begin
select count(*) into l_count from employee
where dept_num = department_id_in;
if l_count > 0 then
raise still_have_employees;
end if;
delete from department where dept_num = department_id_in;
exception
when still_have_employees
then
dbms_output.put_line
('Please delete employees for the department first.');
end;
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Associate Exception Name
procedure delete_department(department_id_in in number)
is
still_have_employees exception;
pragma exception_init (still_have_employees, -2292);
begin
delete from department where dept_num = department_id_in;
exception
when still_have_employees
then
dbms_output.put_line
('Please delete employees for the department first.');
end;
ORA-2292 violated integrity constraining (OWNER.CONSTRAINT) –
child record found.
The PRAGMA keyword is used to signify that the remainder of the PL/SQL
statement is a pragma, or directive, or pseudoinstruction to the compiler.
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Associate Exception Name
EXCEPTION_INIT
Compile-time command or pragma
Shot for pragmatic information
Instructs the compiler to associate an identifier,
declared as an EXCEPTION, with a specific error
number
The error number cannot be:
-1403 (error code for NO_DATA_FOUND), use 100
instead
0 or any positive number besides 100
A negative number less than -1000000
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Associate Exception Name
Centralize EXCEPTION_INIT into packages
CREATE OR REPLACE PACKAGE dynsql
IS
invalid_table_name EXCEPTION;
PRAGMA EXCEPTION_INIT (invalid_table_name, -903);
invalid_column_name EXCEPTION;
PRAGMA EXCEPTION_INIT (invalid_column_name, -904);
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Raise Exception
Oracle might raise the exception when
it detects an error
Programmer might raise an exception
with the RAISE statement
RAISE exception_name;
RAISE package_name.exception_name;
RAISE; -- propagate out
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Raise Exception
DECLARE invalid_id EXCEPTION;
id_value VARCHAR2(30);
BEGIN id_value := id_for ('SMITH');
IF SUBSTR (id_value, 1, 1) != 'X' THEN
RAISE invalid_id;
END IF; ...
END;
IF days_overdue (isbn_in, borrower_in) > 365 THEN
RAISE overdue_pkg.book_is_lost;
END IF;
EXCEPTION
WHEN NO_DATA_FOUND THEN
-- record all the "context" information
errlog.putline (company_id_in);
-- pass NO_DATA_FOUND unhandled
RAISE;
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Handling Exception
Exception handlers are structured much like a
conditional CASE statement
Property
Description
EXCEPTION
WHEN NO_DATA_FOUND
THEN
executable_statements1;
If the NO_DATA_FOUND
exception is raised, then
execute the first set of
statements.
WHEN payment_overdue
THEN
executable_statements2;
WHEN OTHERS
THEN
executable_statements3;
END;
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If the payment is overdue, then
execute the second set of
statements
If any other exception is
encountered, then execute the
third set of statements.
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Handling Exception
PROCEDURE add_employee (
ssn in varchar2, fname in varchar2, lname in varchar2,
dept_num in number, code in number, sup_ssn in varchar2)
IS
BEGIN
insert into employee values
(ssn, fname, lname, dept_num, code, sup_ssn);
EXCEPTION
WHEN OTHERS THEN
DECLARE
l_errcode PLS_INTEGER := SQLCODE;
BEGIN
IF l_errcode = -1 THEN
DBMS_OUTPUT.put_line ('Employee ID already in use.');
RAISE;
ELSIF l_errcode = -2291 THEN
DBMS_OUTPUT.put_line ('Invalid department ID: ');
RAISE;
ELSE
null;
RAISE;
END IF;
END;
END add_employee;
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Combing Multiple Exceptions
DECLARE
l_department department%ROWTYPE;
BEGIN
SELECT * INTO l_department
FROM department
WHERE dept_num = 3;
DBMS_OUTPUT.PUT_LINE(l_department.dept_name);
EXCEPTION
WHEN NO_DATA_FOUND OR TOO_MANY_ROWS
THEN
DBMS_OUTPUT.PUT_LINE('Wrong department number!');
END;
/
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Named System Exception
P. 133
CURSOR_ALREADY_OPEN
DUP_VAL_ON_INDEX
INVALID_CURSOR
INVALID_NUMBER
NO_DATA_FOUND
TOO_MANY_ROWS
VALUE_ERROR
ZERO_DIVIDE
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(ORA-06511)
(ORA-00001)
(ORA-01001)
(ORA-01722)
(ORA-01403)
(ORA-01422)
(ORA-06502)
(ORA-01476)
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SQLCODE and SQLERRM
Built-in Error Functions
SQLCODE
Return the oracle error number
SQLERRM
Return the oracle message text associated with the error
begin
insert into employee values
('666666666', 'Dave', 'Letterman', NULL, 4581.12, NULL);
exception
when others then
dbms_output.put_line('code : ' || sqlcode);
dbms_output.put_line('message : ' || sqlerrm);
if sqlcode = -1 then
dbms_output.put_line
('Employee number exists!');
end if;
end;
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SQLCODE and SQLERRM
PROCEDURE DELETE_COMPANY (COMPANY_ID IN NUMBER)
IS
BEGIN
DELETE FROM COMPANY WHERE COMPANY_ID = COMPANY_ID_IN;
EXCEPTION
WHEN OTHERS
THEN
DECLARE
ERROR_CODE NUMBER := SQLCODE;
ERROR_MSG VARCHAR2(512) := SQLERRM;
BEGIN
IF ERROR_CODE = -2292
/*CHILD RECORDS FOUND*/
THEN
DELETE FROM EMPLOYEE WHERE COMPANY_ID = COMPANY_ID_IN;
DELETE FROM COMPANY WHERE COMPANY_ID = COMPANY_ID_IN;
ELSIF ERROR_CODE = -2291
/*PARENT KEY NOT FOUND*/
THEN
DBMS_OUTPUT.PUT_LINE(‘INVALID COMPANY ID: ’||TO_CHAR(COMPANY_ID_IN));
ELSE
DBMS_OUTPUT.PUT_LINE(‘ERROR DELETING COMPANY, ERROR: ’||ERROR_MSG);
END IF;
END;
END DELETE_COMPANY;
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DML in PL/SQL
INSERT
INSERT INTO table VALUES (val1, …);
INSERT INTO table AS SELECT …;
UPDATE
UPDATE table SET col1 = val1 WHERE …
DELETE
DELETE FROM table WHERE …
Cursor attributes for DML operations
SQL%FOUND, SQL%NOTFOUND,
SQL%ROWCOUNT, SQL%ISOPEN
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DML in PL/SQL
Use SQL%FOUND to determine if your DML
statement affected any rows
CREATE OR REPLACE PROCEDURE change_author_name (
old_name_in IN books.author%TYPE,
new_name_in IN books.author%TYPE,
changes_made_out OUT BOOLEAN)
IS
BEGIN
UPDATE books
SET author = new_name_in
WHERE author = old_name_in;
changes_made_out := SQL%FOUND;
END;
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DML in PL/SQL
Use SQL%ROWCOUNT when you need to
know exactly how many rows were affected
by your DML statement
CREATE OR REPLACE PROCEDURE change_author_name (
old_name_in IN books.author%TYPE,
new_name_in IN books.author%TYPE,
rename_count_out OUT PLS_INTEGER)
IS
BEGIN
UPDATE books
SET author = new_name_in
WHERE author = old_name_in;
rename_count_out := SQL%ROWCOUNT;
END;
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RETURNING Clause
Use returning clause with DML and retrieve
information directly into variables
Declare
l_name employee.lname%type;
l_code employee.code%type;
Begin
for rec in (select * from employee)
loop
update employee
set code = rec.code*1.10
where ssn = rec.ssn
returning code, lname
into l_code, l_name;
dbms_output.put_line
('New code for ' || l_name || ' = ' || l_code);
end loop;
End;
/
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Use Records in Insert and Update
procedure add_employee(emp_in in employee%rowtype)
is
begin
insert into employee values emp_in;
end;
declare
new_employee employee%rowtype;
begin
new_employee.ssn := '123123124';
new_employee.fname := 'Steve';
new_employee.lname := 'Hack';
new_employee.dept_num := '1';
new_employee.code := 123.45;
new_employee.sup_ssn := '600000001';
add_employee(new_employee);
new_employee.code := 333.09;
update employee set row = new_employee
where ssn = new_employee.ssn;
end;
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Use Records in Insert and Update
Using records with the RETURNING clause
DECLARE
my_book_new_info books%ROWTYPE;
my_book_return_info books%ROWTYPE;
BEGIN
my_book_new_info.isbn := '1-56592-335-9';
my_book_new_info.title := 'ORACLE PL/SQL PROGRAMMING';
my_book_new_info.summary := 'General user guide and reference';
my_book_new_info.author := 'FEUERSTEIN, STEVEN AND BILL PRIBYL';
my_book_new_info.page_count := 980;
UPDATE books
SET ROW = my_book_new_info
WHERE isbn = my_book_new_info.isbn
RETURNING isbn, title, summary, author, page_count
INTO my_book_return_info;
END;
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Transaction Management
Commit – save all outstanding changes
Rollback – erase all outstanding changes
Savepoint
SAVEPOINT savepoint_name;
Rollback to savepoint
ROLLBACK TO savepoint_name;
Lock table
LOCK TABLE emp, dept IN SHARE MODE
LOCK TABLE emp IN ROW EXCLUSIVE MODE
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Autonomous Transaction
procedure add_emp(…)
is
MT begins
begin
update …;
update …;
savepoint start_add;
insert …;
MT suspends
commit;
exception
when others
then
rollback to start_add;
write_log
(sqlcode, sqlerrm);
end;
procedure write_log(…)
is
pragma
AT begins
autonomous_transaction;
begin
insert into log values (
code, text,
user, sysdate);
commit;
AT ends
end;
MT resumes
MT ends
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Autonomous Transaction
Define a PL/SQL block as autonomous
transaction
anonymous block, procedure, function,
packaged procedure, packaged function,
database trigger
Isolate the DML in that block from the
caller's transaction context
The block becomes an independent
transaction
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Package
A package is a grouping or packaging of
PL/SQL code elements
Package specification
Definition or specification of all the publicly
available elements in the package
Package body
Code required to implement elements
defined in the package specification
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Favorites_pkg Specification
Favorites_pkg (p. 625)
CREATE OR REPLACE PACKAGE favorites_pkg
AUTHID CURRENT_USER
IS
c_chocolate CONSTANT PLS_INTEGER := 16;
c_strawberry CONSTANT PLS_INTEGER := 29;
TYPE codes_nt IS TABLE OF INTEGER;
my_favorites codes_nt;
TYPE fav_info_rct IS REF CURSOR RETURN favorites%ROWTYPE;
PROCEDURE show_favorites (list_in IN codes_nt);
FUNCTION most_popular RETURN fav_info_rct;
END favorites_pkg;
/
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Favorites_pkg Body
Body (p.627)
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CREATE OR REPLACE PACKAGE BODY favorites_pkg
IS
g_most_popular PLS_INTEGER := c_strawberry;
PROCEDURE show_favorites (list_in IN codes_nt)
IS
BEGIN
FOR indx IN list_in.FIRST .. list_in.LAST
LOOP
DBMS_OUTPUT.put_line (list_in (indx));
END LOOP;
END show_favorites;
FUNCTION most_popular
RETURN fav_info_rct
IS
retval fav_info_rct;
null_cv fav_info_rct;
BEGIN
OPEN retval FOR
SELECT * FROM favorites
WHERE code = g_most_popular;
RETURN retval;
EXCEPTION
WHEN NO_DATA_FOUND THEN
RETURN null_cv;
END most_popular;
END favorites_pkg;
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Package Specification
CREATE OR REPLACE PACKAGE EMPLOYEE_PKG
AS
SUBTYPE FULLNAME_T IS VARCHAR2 (200);
FUNCTION FULLNAME (
LAST_IN EMPLOYEE.LNAME%TYPE,
FIRST_IN EMPLOYEE.FNAME%TYPE)
RETURN FULLNAME_T;
FUNCTION FULLNAME (
EMPLOYEE_SSN_IN IN EMPLOYEE.SSN%TYPE)
RETURN FULLNAME_T;
END EMPLOYEE_PKG;
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Package Body
CREATE OR REPLACE PACKAGE BODY EMPLOYEE_PKG
AS
FUNCTION FULLNAME (
LAST_IN EMPLOYEE.LNAME%TYPE,
FIRST_IN EMPLOYEE.FNAME%TYPE)
RETURN FULLNAME_T
IS
BEGIN
RETURN LAST_IN || ', ' || FIRST_IN;
END;
FUNCTION FULLNAME (EMPLOYEE_SSN_IN IN EMPLOYEE.SSN%TYPE)
RETURN FULLNAME_T
IS
RETVAL FULLNAME_T;
BEGIN
SELECT FULLNAME (LNAME, FNAME) INTO RETVAL
FROM EMPLOYEE
WHERE SSN = EMPLOYEE_SSN_IN;
RETURN RETVAL;
EXCEPTION
WHEN NO_DATA_FOUND THEN RETURN NULL;
WHEN TOO_MANY_ROWS THEN RETURN NULL;
END;
END EMPLOYEE_PKG;
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Calling Packaged Elements
Package is a container for code
elements
Run or reference elements in a package
From outside of that package, use dot
notation
package_name.element_name
Within the package (specification or body),
no need to include the name of the
package
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Pets_inc Package
CREATE OR REPLACE PACKAGE pets_inc
IS
max_pets_in_facility CONSTANT INTEGER := 120;
pet_is_sick EXCEPTION;
CURSOR pet_cur (pet_id_in in pet.id%TYPE)
RETURN pet%ROWTYPE;
FUNCTION next_pet_shots (pet_id_in IN
pet.id%TYPE) RETURN DATE;
PROCEDURE set_schedule (pet_id_in IN
pet.id%TYPE);
END pets_inc;
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Pets_inc Package
CREATE OR REPLACE PACKAGE BODY pets_inc
IS
CURSOR pet_cur (pet_id_in IN pet.id%TYPE) RETURN pet%ROWTYPE
IS
SELECT *
FROM pet p
WHERE p.id = pet_id_in;
FUNCTION next_pet_shots (pet_id_in IN pet.id%TYPE)
RETURN DATE
/* This Implementation is Just a Stub, Presumably to be Replaced by
Something that Does Something Meaningful Later On */
IS
BEGIN
RETURN SYSDATE;
END next_pet_shots;
PROCEDURE set_schedule
/* This Implementation
/* Something that Does
IS
BEGIN
/* Null is a No-Op.
/* The Statement is
NULL;
END;
END pets_inc;
/
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(pet_id_in IN pet.id%TYPE)
is Just a Stub, Presumably to be Replaced by */
Something Meaningful Later On */
*/
Included to Satisfy the Compile-Time Syntax-Checker */
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Pets_inc Package
declare
c_pet constant pet.id%type:=1099;
v_net_appointment date;
begin
if pets_inc.max_pets_in_facility > 100
then
open pets_inc.pet_cur(c_pet);
else
v_next_appointment:=pets_inc.next_pet_shots(c_pet);
end if;
exception
when pets_inc.pet_is_sick
then
pets_inc.set_scheducle(c_pet);
end;
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Package Data
Package level data
Persist for the session
Public and private data
State of the packaged cursors persists
for the session
Open/fetch/close it in different program
Close packaged cursor promptly
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Packaged Cursors
CREATE OR REPLACE PACKAGE book_info
IS
CURSOR byauthor_cur (
author_in IN books.author%TYPE
)
IS
SELECT * FROM books WHERE author = author_in;
CURSOR bytitle_cur (
title_filter_in IN books.title%TYPE
) RETURN books%ROWTYPE;
TYPE author_summary_rt IS RECORD (
author books.author%TYPE,
total_page_count PLS_INTEGER,
total_book_count PLS_INTEGER);
CURSOR summary_cur (
author_in IN books.author%TYPE
) RETURN author_summary_rt;
END book_info;
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Packaged Cursors
CREATE OR REPLACE PACKAGE BODY book_info
IS
CURSOR bytitle_cur (
title_filter_in IN books.title%TYPE
) RETURN books%ROWTYPE
IS
SELECT * FROM books
WHERE title LIKE UPPER (title_filter_in);
CURSOR summary_cur (
author_in IN books.author%TYPE
) RETURN author_summary_rt
IS
SELECT author, SUM (page_count), COUNT (*)
FROM books
WHERE author = author_in;
END book_info;
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Packaged Cursors
DECLARE
onebook book_info.bytitle_cur%ROWTYPE;
BEGIN
OPEN book_info.bytitle_cur ('%PL/SQL%');
LOOP
EXIT WHEN book_info.bytitle_cur%NOTFOUND;
FETCH book_info.bytitle_cur INTO onebook;
book_info.display (onebook);
END LOOP;
CLOSE book_info.bytitle_cur;
END;
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Use of Packages
Encapsulating data manipulation
Avoiding the hardcoding of literals
Grouping together logically related
functionality
Caching session-static data to improve
application performance
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Homework
Given the package code and the database
table.
List the sequence of procedure and function
calls initiated for the PL/SQL command.
What is the output for the PL/SQL
command?
Add exception handling in function.
Lab activities
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