问题
This package uses two unique features of Oracle, REF_CURSOR and a package global variable. I would like to port the functionality from Oracle to Postgresql or MySQL.
PACKAGE tox IS
/*=======================*/
g_spool_key spool.key%TYPE := NULL;
TYPE t_spool IS REF CURSOR RETURN spool%ROWTYPE;
/*=======================*/
PROCEDURE begin_spool;
/*=======================*/
PROCEDURE into_spool
(
in_txt IN spool.txt%TYPE
);
/*=======================*/
PROCEDURE reset_spool;
/*=======================*/
FUNCTION end_spool
RETURN t_spool;
/*=======================*/
FUNCTION timestamp
RETURN VARCHAR2;
/*=======================*/
END tox;
PACKAGE BODY tox
IS
/*========================================================================*/
PROCEDURE begin_spool
AS
/*=======================*/
BEGIN
/*=======================*/
SELECT
key.NEXTVAL
INTO
g_spool_key
FROM
DUAL;
/*=======================*/
END begin_spool;
/*========================================================================*/
PROCEDURE into_spool
(
in_txt IN spool.txt%TYPE
)
AS
/*=======================*/
BEGIN
/*=======================*/
INSERT INTO
spool
VALUES
(
g_spool_key,
in_txt,
seq.NEXTVAL
);
/*=======================*/
END into_spool;
/*========================================================================*/
PROCEDURE reset_spool
AS
/*=======================*/
BEGIN
/*=======================*/
DELETE
spool
WHERE
key = g_spool_key;
COMMIT;
begin_spool;
/*=======================*/
END reset_spool;
/*========================================================================*/
FUNCTION end_spool
RETURN t_spool
AS
v_spool t_spool;
/*=======================*/
BEGIN
/*=======================*/
COMMIT;
OPEN v_spool FOR
SELECT
*
FROM
spool
WHERE
key = g_spool_key
ORDER BY
seq;
RETURN v_spool;
/*=======================*/
END end_spool;
/*========================================================================*/
FUNCTION timestamp
RETURN VARCHAR2
AS
/*-----------------------*/
v_result VARCHAR2(14);
/*=======================*/
BEGIN
/*=======================*/
SELECT
TO_CHAR(SYSDATE,'YYYYMMDDHH24MISS')
INTO
v_result
FROM
DUAL;
RETURN v_result;
/*=======================*/
END timestamp;
/*========================================================================*/
END tox;
Can you produce the equivalent code? for Postgresql? for MySQL?
Note: The Oracle code is thread safe. This is a key feature.
回答1:
PostgreSQL 8.3
The problem in PostgreSQL is the lack of global (or package) variables, so that part has to be solved with a temp-table that is created first. The rest of it was quite easy.
If you are serious about porting the application over to PostgreSQL or MySQL, I would recommend you to not use global variables at all since they are bad practice when coding (according to me at least :))
But anyway, here is the code:
This has to exist before running the functions:
create table spool (key integer, txt varchar(2048), seq integer);
create sequence s_key;
create sequence s_seq;
create schema tox;
create temp table globals (name varchar(10), value varchar(100), primary key(name));
The functions are being put in the schema tox to simulate a package.
create or replace function tox.get_variable(var_name varchar) returns varchar as $$
declare
ret_val varchar(100);
begin
select value into ret_val from globals where name = var_name;
return ret_val;
end
$$ language plpgsql;
create or replace function tox.set_variable(var_name varchar, value anyelement) returns void as $$
begin
delete from globals where name = var_name;
insert into globals values(var_name, value);
end;
$$ language plpgsql;
create or replace function tox.begin_spool() returns integer as $$
begin
perform tox.set_variable('key', nextval('s_key')::varchar);
return tox.get_variable('key');
end;
$$ language plpgsql;
create or replace function tox.reset_spool() returns integer as $$
begin
delete from spool where key = tox.get_variable('key')::integer;
return tox.begin_spool();
end;
$$ language plpgsql;
create or replace function tox.into_spool(in_txt spool.txt%TYPE) returns void as $$
begin
insert into spool values(tox.get_variable('key')::integer, in_txt, nextval('s_seq'));
end;
$$ language plpgsql;
create or replace function tox.end_spool(refcursor) returns refcursor as $$
declare
begin
open $1 for select * from spool where key = tox.get_variable('key')::integer order by seq;
return $1;
end;
$$ language plpgsql;
create or replace function tox.test(txt varchar(100)) returns setof spool as $$
declare
v_spool_key integer;
cnt integer;
begin
v_spool_key = tox.begin_spool();
for cnt in 1..10 loop
perform tox.into_spool(txt || cnt);
end loop;
perform tox.end_spool('spool_cursor');
return query fetch all from spool_cursor;
end;
$$ language plpgsql;
To test, just run this after everything have been created.
select * from tox.test('Test');
回答2:
For mysql:
- For ref_cursor you can just use a regular select in a procedure. Mysql has an implicit result set that is returned from stored procedure if you issue a select statement. See my answer here.
- For the package global variable, you can put it in a table, but it appears from your code that it is a sequence, so it can be replaced with an auto_increment field. That should be pretty simple.
It would help if you can post the definition of your spool table in the question. Then I could probably provide you with exact code for mysql.
回答3:
I have a hard time understanding several things in your code. It looks like you have a table with two sequences, but only one of them is truly an auto_increment column.
In mysql auto_increment is allowed only on one column in a table. have you considered making the other column a foreign key to an auto incremented column of another table?
The global variable is tricky, because mysql doesn't have them. I think the only resolution is to store it as a scalar in a table, and then tie your data to it with a foreign key.
Finally, returning a ref cursor is easy, as I pointed out in my previous answer. In the link provide (to a different answer) you can see a code sample.
回答4:
Here's a solution tested with MySQL 5.1.30.
Regarding your requirement for thread-safety, the MySQL User Variable mechanism should help. This allows you to SET a variable whose state is limited to the current session. Other sessions can also create a variable by the same name, and keep a different value in it.
I assume by thread-safety you mean something like this -- session-scoped state. Because you can't really have more fine-grained thread-safe state in a database. Each thread of your application must have its own session to the database.
There are no packages in MySQL, so the user variable is global to the session. Another stored procedure that happens to use a variable of the same name will conflict.
CREATE TABLE spool (
`key` INT,
txt VARCHAR(2048),
seq INT AUTO_INCREMENT PRIMARY KEY
);
CREATE TABLE spool_key (
`key` INT AUTO_INCREMENT PRIMARY KEY
);
DELIMITER $$
CREATE PROCEDURE begin_spool ()
BEGIN
DELETE FROM spool_key;
INSERT INTO spool_key (`key`) VALUES (DEFAULT);
SET @sp_key = LAST_INSERT_ID();
END $$
CREATE PROCEDURE into_spool(IN in_txt VARCHAR(2048))
BEGIN
INSERT INTO spool (`key`, txt, seq) VALUES
(@sp_key, in_txt, DEFAULT);
END $$
CREATE PROCEDURE reset_spool()
BEGIN
DELETE spool FROM spool JOIN spool_key USING (`key`);
CALL begin_spool();
END $$
CREATE PROCEDURE end_spool()
BEGIN
SELECT *
FROM spool JOIN spool_key USING (`key`)
ORDER BY seq;
END $$
DELIMITER ;
CALL begin_spool();
CALL into_spool('now is the time');
CALL into_spool('for all good men');
CALL end_spool();
CALL reset_spool();
CALL into_spool('to come to the aid');
CALL into_spool('of their country');
CALL end_spool();
DROP FUNCTION IF EXISTS fmt_timestamp;
CREATE FUNCTION fmt_timestamp() RETURNS CHAR(14)
RETURN DATE_FORMAT(SYSDATE(), '%Y%m%d%H%i%s');
SELECT fmt_timestamp();
来源：https://stackoverflow.com/questions/489441/convert-oracle-stored-procedure-using-ref-cursor-and-package-global-variable-to