Skip to main content

::Pipelined in Oracle as well in PostgreSQL::

Pipelined Table Functions:- [ORACLE]
===========================

If you want to return multiple rows to the calling environment, then piplined table functions is prefred. It will increase the dbperformance as well.

Ex:-

Step 1:
-----------
CREATE TABLE EMP(EMPNO INT,ENAME VARCHAR2(10),SAL INT);

Step 2:
-----------
Insert sample data.

Step 3:
-----------
Create an object for the row type casting.
CREATE OR REPLACE TYPE emp_row
AS OBJECT
(
empno INT,
ename VARCHAR2(20),
SAL INT
);

Step 4:
-----------
Create a Return Type for the pipelined function.
CREATE OR REPLACE TYPE emp_table_type
AS TABLE OF emp_row;

Step 5:
-----------
CREATE OR REPLACE FUNCTION emp_pipe_function RETURN emp_table_type PIPELINED IS
BEGIN
FOR rec in (select * from emp)
LOOP
PIPE ROW (emp_row(rec.empno,rec.ename,rec.sal));
END LOOP;
RETURN;
END;


Step 6:
----------
SQL> select * from table(emp_pipe_function);

EMPNO ENAME SAL
---------- -------------------- ----------
1 Dinesh 1000
2 MANOJA 2000
3 SREE VANI 3000
4 NIVAS 4000

SQL> select * from emp;

EMPNO ENAME SAL
---------- ---------- ----------
1 Dinesh 1000
2 MANOJA 2000
3 SREE VANI 3000
4 NIVAS 4000

Same Case In PostgreSQL
=========================

Step 1:
---------
CREATE TABLE EMP(ENO INT,ENAME VARCHAR,SAL INT);

Step 2:
---------
Insert Sample Rows

Step 3:
---------
CREATE OR REPLACE FUNCTION EMP_FUNC() RETURNS SETOF PUBLIC.EMP
AS
$$
SELECT * FROM EMP;
$$
LANGUAGE SQL;

(OR)

CREATE OR REPLACE FUNCTION EMP_FUNC() RETURNS SETOF PUBLIC.EMP
AS
$$
BEGIN
RETURN QUERY SELECT * FROM EMP;
END;
$$
LANGUAGE PLPGSQL;

(OR)

CREATE OR REPLACE FUNCTION EMP_FUNC() RETURNS SETOF PUBLIC.EMP AS
$$
DELCARE
T RECORD;
BEGIN
FOR  T IN SELECT * FROM EMP
LOOP
RETURN NEXT T;
END LOOP;
END;
$$
LANGUAGE PLPGSQL;

Step 4:
----------
postgres=# SELECT * FROM EMP_FUNC();
eno | ename | sal
-----+-----------+------
1 | Dinesh | 1000
2 | MANOJA | 2000
3 | SREE VANI | 3000
4 | NIVAS | 4000
(4 rows)

postgres=# SELECT * FROM EMP;
eno | ename | sal
-----+-----------+------
1 | Dinesh | 1000
2 | MANOJA | 2000
3 | SREE VANI | 3000
4 | NIVAS | 4000
(4 rows)

Comments

  1. Hello. First sorry for my english and for my keyboard (I'm writting with my phone).
    I'd like "throw" more than a single line, like i did with Oracle PL/SQL, for each iteration of the loop. Here is an example:
    for rec in cursor
    loop
    row.col1 := rec.col1;
    ...
    if rec.colX = 'TRUE'
    then
    row.colWhen = 'Morning';
    pipe row (row);
    end if;
    if rec.colY = 'TRUE'
    then
    row.colWhen = 'Afternoom';
    pipe row (row);
    end if;
    if rec.colZ = 'TRUE'
    then
    row.colWhen = 'Night';
    pipe row (row);
    end if;
    end loop;
    As you see, the script is able to send from 0 to 3 lines at every iteration of the cursor.
    I'm too noob in plpgsql to do it. I need some help. Can you and can plpgsql do it?
    Thanks a lot.

    ReplyDelete
    Replies
    1. Precision: cols colX, colY and colZ are result of decode / case function of which pl language is used.

      Delete
  2. Does it work for you.

    CREATE OR REPLACE FUNCTION EMP_FUNC() RETURNS SETOF TEXT AS
    $$
    DECLARE
    T RECORD;
    T1 RECORD;
    BEGIN
    FOR T IN SELECT * FROM EMP
    LOOP
    IF T.SAL <=1000 THEN
    SELECT 'LOW' INTO T1;
    ELSIF T.SAL <=2000 THEN
    SELECT 'MEDIUM' INTO T1;
    ELSIF T.SAL <=3000 THEN
    SELECT 'HIGH' INTO T1;
    ELSIF T.SAL <=4000 THEN
    SELECT 'VERY HIGH' INTO T1;
    END IF;
    RETURN NEXT T1;
    END LOOP;
    RETURN;
    END;
    $$
    LANGUAGE PLPGSQL;

    Thanks,
    Dinesh

    ReplyDelete
  3. Hi.
    Thanks for your answer.
    Your example does'nt return what I expect.
    In your example, I'd like every t.sal <=2000 return 2 lines (LOW and MEDIUM), every t.sal <=3000 return 3 lines ( LOW, MEDIUM and HIGH) and of course, every t.sal <= 4000 return 4 lines...
    That's what my PL/SQL code does, but I don't know how to do the same with PLPGSQL. Every «RETURN NEXT» sends the last value of T1.
    I think when Oracle reads an instruction PIPE ROW, it sends a ROW. If only I could write the equivalent in each IF - END IF block...

    What do you think about it? My code is too "poor", isn't it?

    ReplyDelete
  4. I found a cheat!!!

    CREATE OR REPLACE FUNCTION EMP_FUNC() RETURNS SETOF TEXT AS
    $$
    DECLARE
    T RECORD;
    BEGIN
    FOR T IN SELECT * FROM EMP ORDER BY SAL DESC
    LOOP
    IF T.SAL <=1000 THEN
    RETURN QUERY SELECT 'LOW';
    ELSIF T.SAL <=2000 THEN
    RETURN QUERY SELECT 'LOW';
    RETURN QUERY SELECT 'MEDIUM';
    ELSIF T.SAL <=3000 THEN
    RETURN QUERY SELECT 'LOW';
    RETURN QUERY SELECT 'MEDIUM';
    RETURN QUERY SELECT 'HIGH';
    ELSIF T.SAL <=4000 THEN
    RETURN QUERY SELECT 'LOW';
    RETURN QUERY SELECT 'MEDIUM';
    RETURN QUERY SELECT 'HIGH';
    RETURN QUERY SELECT 'VERY HIGH';
    END IF;
    END LOOP;
    RETURN;
    END;
    $$
    LANGUAGE PLPGSQL;

    I can't find, now, a better way to do it. I dislike this code, but i does what I want.

    Do you have better?

    ReplyDelete
  5. Hi Fred,

    Sorry for the late reply, i was bit busy in some other stuff.

    Does it work for you.

    CREATE OR REPLACE FUNCTION EMP_FUNC1() RETURNS SETOF TEXT[] AS
    $$
    DECLARE
    T RECORD;
    BEGIN
    FOR T IN SELECT * FROM EMP ORDER BY SAL DESC
    LOOP
    IF T.SAL <=1000 THEN
    RETURN NEXT ARRAY['LOW'];
    ELSIF T.SAL <=2000 THEN
    RETURN NEXT ARRAY['LOW', 'MEDIUM'];
    ELSIF T.SAL <=3000 THEN
    RETURN NEXT ARRAY['LOW', 'MEDIUM', 'HIGH'];
    END IF;
    END LOOP;
    RETURN;
    END;
    $$
    LANGUAGE PLPGSQL;

    postgres=# SELECT * from emp_func1();
    emp_func1
    -------------------
    {LOW,MEDIUM,HIGH}
    {LOW,MEDIUM}
    {LOW}
    (3 rows)


    postgres=# SELECT unnest(emp_func1());
    unnest
    --------
    LOW
    MEDIUM
    HIGH
    LOW
    MEDIUM
    LOW
    (6 rows)

    Thanks,
    Dinesh

    ReplyDelete

Post a Comment

Popular posts from this blog

How To Send E-Mail From PostgreSQL

Hi ,

If you want to send E-Mails from PostgreSQL, then use the below Python 3.2 Script as below. I have used ActivePython 3.2 with PostgreSQL 9.1 for sending E-Mails from PostgreSQL.

If you want to configure the Python 3.2 with PostgreSQL 9.1 then, please refer the below steps.

http://manojadinesh.blogspot.in/2012/06/fatal-python-error-pyinitialize-unable.html

Once, your Python 3.2 successful then follow the below steps to send an e-mail.

Step 1
=====

postgres=# CREATE OR REPLACE FUNCTION public.send_email(_from Text,_password Text,smtp Text,port INT,receiver text, subject text, send_message text) RETURNS TEXT  LANGUAGE plpython3u
AS $function$

import smtplib
sender = _from
receivers = receiver
message = ("From: %s\nTo: %s\nSubject: %s\n\n %s"
 % (_from,receiver,subject,send_message))

try:

  smtpObj = smtplib.SMTP(smtp,port)
  smtpObj.starttls()
  smtpObj.login(_from, _password)
  smtpObj.sendmail(sender, receivers,message)
  print ('Successfully sent email')
except SMTPException…

DBLINK in PostgreSQL

Hi,

Find the below DBLINK concepts in PostgreSQL, PostgresPlus as well.


PostgreSQL
----------
Foreign Data Wrapper
--------------------
This is the one utility which encapsulates the data from the different Database servers using Handler functions.

Ex:- In PG 9.1, we can encapsulates the data from My Sql and store to PostgreSQL using handlers.
CREATE FOREIGN DATA WRAPPER HANDLER VALIDATOR ;

Currently(<= 9.0) PostgreSQL compatible with only remote PostgreSQL. From 9.1 onwards, we can make the PostgreSQL to communicate with SQL Server/My SQL through these wrappers. Servers ------- This is the one object which is having the Data wrapper methodology as well the remote host connectivity details. Ex:- CREATE SERVER FOREIGN DATA WRAPPER OPTIONS (address , port ,dbname );

User Mapping
------------
This is the one object which maps the current dbserver user/role to remote dbserver user.

Ex:-CREATE USER MAPPING FOR SERVER OPTIONS (username , password );

DBLINK
------
Dblink is one o…

:: Rownum in postgresql ::

Hi All,

As we know,we can generate rownum with window fuctions also(Rank).In oracle we have "rownum" pseduo column,but we don't in postgresql.
Here is the one of the solution for generating rownum in postgresql.

In Oracle
-----------

SQL> CREATE SEQUENCE ROWNUMSEQ;

Sequence created.


SQL> SELECT EMPNO,ROWNUMSEQ.NEXTVAL AS "ROWNUM" FROM EMP;

EMPNO ROWNUM
---------- ----------
7369 1
7499 2
7521 3
7566 4
7654 5
7698 6
7782 7
7788 8
7839 9
7844 10
7876 11
7900 12
7902 13
7934 14


In PostgreSQL
----------------

postgres=# CREATE SEQUENCE ROWNUMSEQ;
CREATE SEQUENCE

postgres=# CREATE TABLE TEST(T INT);
CREATE TABLE

postgres=# INSERT INTO TEST VALUES(GENERATE_SERIES(1,14));
INSERT 0 14


postgres=# SELECT T,NEXTVAL('ROWNUMSEQ') AS ROWNUM FROM TES…