PL/SQL: It’s all in the presentation!
Tim Hall
Oracle ACE Director
Oracle ACE of the Year 2006
OCP DBA (7, 8, 8i, 9i, 10g, 11g)
OCA PL/SQL Developer
http://www.oracle-base.com
Oracle PL/SQL Tuning (Rampant)
Oracle Job Scheduling (Rampant)
http://www.oracle-base.com
PL/SQL: It’s all in the presentation!
• Physical organization of objects
• Present queries from APIs
– Ref cursors
– Table functions and pipelining
• Presenting data as web services and XML
– SOAP web services
– XML over HTTP
– REST web services
http://www.oracle-base.com
Physical organization of objects
Schema Owner
Tables
API Owner
PL/SQL APIs
Views?
Login User
PHP
APEX
Java
http://www.oracle-base.com
.NET
Physical organization of objects
Schema Owner
Tables
API Owner
API Owner
PL/SQL APIs
Login User
PHP
PL/SQL APIs
Login User
APEX
Login User
Java
http://www.oracle-base.com
.NET
Why break things up like this?
• All data access via presentation (API) layer.
–
–
–
–
–
Better security.
Hides processing complexity from clients.
Presentation layer is sharable between applications.
Easier to tune and trace.
Hides schema changes from client applications.
• Table or Transactional APIs?
– Transactional APIs are important to me. APIs that perform
business functions and and are understandable by the business.
– I feel table APIs are unnecessary, but if you like them use them.
– Don’t present table APIs to the outside world.
http://www.oracle-base.com
How do we implement it?
• Use existing techniques to abstract the data:
– Packaged procedures and functions for data processing.
– Ref cursors and pipelined table functions for data presentation.
• schema_setup.sql
http://www.oracle-base.com
Without using APIs
$conn = get_connection();
$sql = "
”;
$stmt
=
$result =
($conn, $sql);
($stmt, OCI_DEFAULT);
while (
$dname
=
$employees =
($stmt)) {
($stmt, "DNAME");
($stmt, "EMPLOYEES");
}
($stmt);
($conn)
basic_query.php
http://www.oracle-base.com
Do views help?
•
•
•
•
Views do reduce complexity of code in client apps.
I prefer not to expose views to client developers.
Risk of client developers writing joins between views.
How would a view affect the previous client code?
v_emps_by_dept
d.dname,
(e.ename)
dept d
emp e
d.dname
d.dname;
employees
e.deptno = d.deptno
web_view.sql
http://www.oracle-base.com
Using a view
$conn = get_connection();
$sql = "
”;
$stmt
=
$result =
($conn, $sql);
($stmt, OCI_DEFAULT);
while (
$dname
=
$employees =
($stmt)) {
($stmt, "DNAME");
($stmt, "EMPLOYEES");
}
($stmt);
($conn);
view_query.php
http://www.oracle-base.com
Cursor variables (REF CURSOR)
• What are they?
– A pointer to current row in multi-row query.
• Why are they useful?
– Allow us to separate opening and processing of cursors.
– Can be passed as parameters.
• Why is that useful to us?
– Allows us to pass resultsets to client applications
• Is that all they can do?
– No, but it gets boring pretty fast…
• Do we have to define REF CURSOR types?
– No. We can be lazy and use SYS_REFCURSOR type.
http://www.oracle-base.com
Returning a cursor from a function
web_rc_api
get_emps_by_dept
l_cursor
;
l_cursor
d.dname,
(e.ename)
dept d
JOIN emp e
d.dname
d.dname;
employees
e.deptno = d.deptno
l_cursor;
get_emps_by_dept;
web_rc_api;
/
web_rc_api.sql
http://www.oracle-base.com
Using ref cursors
$conn = get_connection();
$sql = "
”;
$stmt =
($conn, $sql);
$cursor =
$result =
$result =
($conn);
($stmt, ':rc', $cursor, -1, OCI_B_CURSOR);
($stmt, OCI_DEFAULT);
($cursor, OCI_DEFAULT);
while (
$dname
=
$employees =
($stmt)) {
($stmt, "DNAME");
($stmt, "EMPLOYEES");
}
($stmt);
($conn);
rc_query.php
http://www.oracle-base.com
I don’t have a simple query. What so I do?
• You could use a table function.
• What’s one of those?
– Functions that return collections are known as table functions.
• How can that help me?
– In combination with the TABLE function, they can be used in the
FROM clause of a query like a regular table.
tf_test.sql
• For regular table functions, the collection must be defined
using database OBJECT types.
• Is that all I need to know?
– Not really. You need to know about pipelining.
http://www.oracle-base.com
Pipelining table functions
• A table function builds the entire collection before returning
any data, while a pipelined table function “pipes” each row out
as soon as it is created.
• How does that help me?
– It reduces first row lag…
ptf_schema.sql, ptf_package.sql, ptf_query.sql
– As the collection is never fully resident in memory, pipelining can
produce a considerable memory saving.
memory_usage.sql
– Since 9i R2, the types used to define the pipelined table function
can be defined in a package, but this method can produce
management problems, so I prefer the explicit method.
implicit_types.sql
• But how does that really help me?
– You can use PL/SQL to build the row then pass it out.
http://www.oracle-base.com
Defining a Pipelined table Function
web_ptf_api.sql
http://www.oracle-base.com
Using a pipelined table function
$conn = get_connection();
$sql = "
”;
$stmt
=
$result =
($conn, $sql);
($stmt, OCI_DEFAULT);
while (
$dname
=
$employees =
($stmt)) {
($stmt, "DNAME");
($stmt, "EMPLOYEES");
}
($stmt);
($conn);
ptf_query.php
http://www.oracle-base.com
Can we improve on this?
• We can combine Pipelined Table Functions and Ref Cursors.
web_rc_ptf_api.sql
• How will that affect the client code?
http://www.oracle-base.com
RC & PTF together (rc_ptf_query.php)
$conn = get_connection();
$sql = "
”;
$stmt =
($conn, $sql);
$cursor =
$result =
$result =
($conn);
($stmt, ':rc', $cursor, -1, OCI_B_CURSOR);
($stmt, OCI_DEFAULT);
($cursor, OCI_DEFAULT);
while (
$dname
=
$employees =
($stmt)) {
($stmt, "DNAME");
($stmt, "EMPLOYEES");
}
($stmt);
($conn);
rc_ptf_query.php
http://www.oracle-base.com
What have we shown?
• We can use APIs to hide complexity from client application
developers.
• How do we present queries from our APIs?
– Ref cursors
– Pipelined table functions
– Views?
• Remember: The technology dictates will and won’t want to do
with APIs, not just our ideals.
• Is that the only way we can present data from PL/SQL?
– Certainly not…
http://www.oracle-base.com
Web Services and XML
• eGov AU: Craig Thomler's personal eGovernment and Gov 2.0
thoughts and speculations from an Australian perspective
• Overcoming public sector hurdles to Gov 2.0
http://egovau.blogspot.com/2009/10/overcoming-public-sector-hurdles-to-gov.html
• Choice quotes:
– "...people are generally most comfortable with the technologies
they grew up with...”
– "...government systems are struggling in some areas to keep up
with the rate of change...”
– "If our systems can't support Gov 2.0 initiatives then it is unlikely
that our senior management will.”
http://www.oracle-base.com
Web Services and XML
• What does this have to do with PL/SQL?
– PL/SQL allows you to create web applications, without the learning
curve of Java or .NET.
– Oracle allows you to present existing PL/SQL code as web
services with zero effort.
– Oracle's web toolkit allows you to present data as XML really
easily.
– PL/SQL is mature, not legacy.
http://www.oracle-base.com
XML DB Native Web Services
• Oracle XML DB Native Web Services present your PL/SQL as
Simple Object Access Protocol (SOAP) web services.
• Requires a single configuration step on the database.
• Enabled for “schema” by granting:
– GRANT XDB_WEBSERVICES TO user;
• Optionally:
– GRANT XDB_WEBSERVICES_OVER_HTTP TO user;
– GRANT XDB_WEBSERVICES_WITH_PUBLIC TO user; --?
•
•
•
•
•
web_services_setup.sql
XML DB auto-generates a WSDL file.
We send a SOAP Request and get a SOAP Response returned.
call_ws.pl (run it)
Physical organization of schema keeps things neat.
http://www.oracle-base.com
Physical organization of objects
Schema Owner
Tables
WS API
Owner
API Owner
PL/SQL APIs
PL/SQL APIs
Login User
Java
.NET
http://www.oracle-base.com
APEX
XML over HTTP
• We can also present XML directly from the database.
• First we define a Database Access Descriptor (DAD) to give a
“schema” access to the web toolkit functionality.
xml_api_setup.sql
• Next we define a package to generate our XML.
xml_api.sql (run it)
• This is an incredibly simple way to get XML out of the database.
• Once again, physical organization is important.
http://www.oracle-base.com
XML over HTTP (Semi-Static Data)
• The previous method regenerates the XML each time the URL is
called.
• For semi-static data this is a waste of resources.
• Solution? Generate once and re-present.
• How? Place it in the XML DB file system.
xml_db_setup.sql
• Next we define a procedure to generate our XML.
semi_static.sql
• How do we access this file?
HTTP, FTP access, WebDAV
• This can reduce resource usages.
http://www.oracle-base.com
REST web services
• The previous method is similar to Representational State
Transfer (REST) web services, with the exception of the URL.
• We can mimic REST web services using the EPG parameters:
– PATH-ALIAS
– PATH-ALIAS-PROCEDURE
•
•
•
•
rest_api_setup.sql
rest_api.sql
REST Demo
We can easily code REST web services directly from PL/SQL.
http://www.oracle-base.com
Summary
• Physical organization of objects
– Important for us to present business driven functionality.
• Ref cursors
– Allows us to hide complexity from client applications.
• Table functions
– Allow us to return complex data as if it were a simple query.
• Presenting data as web services and XML is easy using PL/SQL
– Presenting existing PL/SQL code as SOAP web services.
– Producing REST web services from PL/SQL.
• Which all keeps us relevant in the new world order.
• Demo Code: http://www.oracle-base.com/workshops
http://www.oracle-base.com