7. Executing PL/SQL

PL/SQL is a procedural language used for creating user-defined procedures, functions, and anonymous blocks. PL/SQL program units are compiled and run inside Oracle Database, letting them efficiently work on data. Procedures and functions can be stored in the database, encapsulating business logic for reuse in other applications.

PL/SQL code can be stored in the database, and executed using python-oracledb.

Examples in this chapter show single invocations using Cursor.callproc(), Cursor.callfunc(), or Cursor.execute(). Examples of repeated calls using Cursor.executemany() are shown in Batch Execution of PL/SQL.

User-defined procedures in JavaScript

You may also be interested in creating user-defined procedures in JavaScript instead of PL/SQL, see Introduction to Oracle Database Multilingual Engine for JavaScript. These procedures can be invoked in python-oracledb the same way PL/SQL is.

7.1. PL/SQL Stored Procedures

The Cursor.callproc() method is used to call PL/SQL procedures.

If a procedure with the following definition exists:

create or replace procedure myproc (
    a_Value1                            number,
    a_Value2                            out number
) as
begin
    a_Value2 := a_Value1 * 2;
end;

then the following Python code can be used to call it:

out_val = cursor.var(int)
cursor.callproc('myproc', [123, out_val])
print(out_val.getvalue())        # will print 246

Calling Cursor.callproc() internally generates an anonymous PL/SQL block and executes it. This is equivalent to the application code:

cursor.execute("begin myproc(:1,:2); end;", [123, out_val])

See Using Bind Variables for information on binding.

7.2. PL/SQL Stored Functions

The Cursor.callfunc() method is used to call PL/SQL functions.

The first parameter to callfunc() is the function name. The second parameter represents the PL/SQL function return value and is expected to be a Python type, one of the oracledb types or an Object Type. Any following sequence of values or named parameters are passed as PL/SQL function arguments.

If a PL/SQL function with the following definition exists:

create or replace function myfunc (
    a_StrVal varchar2,
    a_NumVal number,
    a_Date out date
) return number as
begin
    select sysdate into a_Date from dual;
    return length(a_StrVal) + a_NumVal * 2;
end;

then the following Python code can be used to call it:

d = cursor.var(oracledb.DB_TYPE_DATE)   # for the a_Date OUT parameter
return_val = cursor.callfunc("myfunc", int, ["a string", 15, d])
print(return_val)        # prints 38
print(d.getvalue())      # like 2024-12-04 22:35:23

A more complex example that returns a spatial (SDO) object can be seen below. First, the SQL statements necessary to set up the example:

create table MyPoints (
    id number(9) not null,
    point sdo_point_type not null
);

insert into MyPoints values (1, sdo_point_type(125, 375, 0));

create or replace function spatial_queryfn (
    a_Id     number
) return sdo_point_type is
    t_Result sdo_point_type;
begin
    select point
    into t_Result
    from MyPoints
    where Id = a_Id;

    return t_Result;
end;
/

The Python code that will call this procedure looks as follows:

obj_type = connection.gettype("SDO_POINT_TYPE")
cursor = connection.cursor()
return_val = cursor.callfunc("spatial_queryfn", obj_type, [1])
print(f"({return_val.X}, {return_val.Y}, {return_val.Z})")
# will print (125, 375, 0)

See Using Bind Variables for information on binding.

7.3. Anonymous PL/SQL Blocks

An anonymous PL/SQL block can be called as shown:

var = cursor.var(int)
cursor.execute("""
        begin
            :out_val := length(:in_val);
        end;""", in_val="A sample string", out_val=var)
print(var.getvalue())        # will print 15

See Using Bind Variables for information on binding.

7.4. Passing NULL values to PL/SQL

Oracle Database requires a type, even for null values. When you pass the value None, then python-oracledb assumes its type is a string. If this is not the desired type, you can explicitly set it. For example, to pass a NULL Oracle Spatial SDO_GEOMETRY object to a PL/SQL stored procedure with the signature:

procedure myproc(p in sdo_geometry)

You can use:

type_obj = connection.gettype("SDO_GEOMETRY")
var = cursor.var(type_obj)
cursor.callproc("myproc", [var])

7.5. Creating Stored Procedures and Packages

To create PL/SQL stored procedures and packages, use Cursor.execute() with a CREATE command. For example:

cursor.execute("""
        create or replace procedure myprocedure
        (p_in in number, p_out out number) as
        begin
            p_out := p_in * 2;
        end;""")

7.5.1. PL/SQL Compilation Warnings

When creating PL/SQL procedures, functions, or types in python-oracledb, the statement might succeed without throwing an error but there may be additional informational messages. These messages are sometimes known in Oracle as “success with info” messages. If your application needs to show such messages, they must be explicitly looked for using Cursor.warning. A subsequent query from a table like USER_ERRORS will show more details. For example:

with connection.cursor() as cursor:

    cursor.execute("""
            create or replace procedure badproc as
            begin
                WRONG WRONG WRONG
            end;""")

    if cursor.warning and cursor.warning.full_code == "DPY-7000":
        print(cursor.warning)

        # Get details
        cursor.execute("""
                select line, position, text
                from user_errors
                where name = 'BADPROC' and type = 'PROCEDURE'
                order by line, position""")
        for info in cursor:
            print("Error at line {} position {}:\n{}".format(*info))

The output would be:

DPY-7000: creation succeeded with compilation errors
Error at line 3 position 23:
PLS-00103: Encountered the symbol "WRONG" when expecting one of the following:

   := . ( @ % ;

7.6. Using the %ROWTYPE Attribute

In PL/SQL, the %ROWTYPE attribute lets you declare a record that represents either a full or partial row of a database table or view.

To work with %ROWTYPE in python-oracledb, use Connection.gettype() to get the relevant attribute type information.

Getting a %ROWTYPE value from PL/SQL

Given a PL/SQL function that returns a row of the LOCATIONS table:

create or replace function TestFuncOUT return locations%rowtype as
  p locations%rowtype;
begin
   select * into p from locations where rownum < 2;
   return p;
end;
/

You can use gettype() to get the type of the PL/SQL function return value, and specify this as the callfunc() return type. For example:

rt = connection.gettype("LOCATIONS%ROWTYPE")
r = cursor.callfunc("TESTFUNCOUT", rt)

The variable r will contain the return value of the PL/SQL function as an Object Type. You can access its contents using the methods discussed in Fetching Oracle Database Objects and Collections. The helper function dump_object() defined there is a convenient example:

dump_object(r)

Output will be:

{
  LOCATION_ID: 1000
  STREET_ADDRESS: '1297 Via Cola di Rie'
  POSTAL_CODE: '00989'
  CITY: 'Roma'
  STATE_PROVINCE: None
  COUNTRY_ID: 'IT'
}

Constructing a %ROWTYPE value in python-oracledb

You can construct a similar object directly in python-oracledb by using DbObjectType.newobject() and setting any desired fields. For example:

rt = connection.gettype("LOCATIONS%ROWTYPE")
r = rt.newobject()
r.CITY = 'Roma'

Passing a %ROWTYPE value into PL/SQL

Given the PL/SQL procedure:

create or replace procedure TestProcIN(p in locations%rowtype, city out varchar2) as
begin
    city := p.city;
end;

you can call callproc() passing the variable r from the previous callfunc() or newobject() examples in the appropriate parameter position, for example:

c = cursor.var(oracledb.DB_TYPE_VARCHAR)
cursor.callproc("TESTPROCIN", [r, c])
print(c.getvalue())

This prints:

Roma

See plsql_rowtype.py for a runnable example.

7.7. Using DBMS_OUTPUT

The standard way to print output from PL/SQL is with the package DBMS_OUTPUT. Note, PL/SQL code that uses DBMS_OUTPUT runs to completion before any output is available to the user. Also, other database connections cannot access the buffer.

To use DBMS_OUTPUT:

• Call the PL/SQL procedure DBMS_OUTPUT.ENABLE() to enable output to be buffered for the connection.

• Execute some PL/SQL that calls DBMS_OUTPUT.PUT_LINE() to put text in the buffer.

• Call DBMS_OUTPUT.GET_LINE() or DBMS_OUTPUT.GET_LINES() repeatedly to fetch the text from the buffer until there is no more output.

For example:

# enable DBMS_OUTPUT
cursor.callproc("dbms_output.enable")

# execute some PL/SQL that calls DBMS_OUTPUT.PUT_LINE
cursor.execute("""
        begin
            dbms_output.put_line('This is the python-oracledb manual');
            dbms_output.put_line('Demonstrating how to use DBMS_OUTPUT');
        end;""")

# tune this size for your application
chunk_size = 100

# create variables to hold the output
lines_var = cursor.arrayvar(str, chunk_size)
num_lines_var = cursor.var(int)
num_lines_var.setvalue(0, chunk_size)

# fetch the text that was added by PL/SQL
while True:
    cursor.callproc("dbms_output.get_lines", (lines_var, num_lines_var))
    num_lines = num_lines_var.getvalue()
    lines = lines_var.getvalue()[:num_lines]
    for line in lines:
        print(line or "")
    if num_lines < chunk_size:
        break

This will produce the following output:

This is the python-oracledb manual
Demonstrating use of DBMS_OUTPUT

An alternative is to call DBMS_OUTPUT.GET_LINE() once per output line, which may be much slower:

text_var = cursor.var(str)
status_var = cursor.var(int)
while True:
    cursor.callproc("dbms_output.get_line", (text_var, status_var))
    if status_var.getvalue() != 0:
        break
    print(text_var.getvalue())

7.8. Implicit Results

Implicit results permit a Python program to consume cursors returned by a PL/SQL block without the requirement to use OUT REF CURSOR parameters. The method Cursor.getimplicitresults() can be used for this purpose. It needs Oracle Database 12.1 (or later). For python-oracledb Thick mode, Oracle Client 12.1 (or later) is additionally required.

An example using implicit results is as shown:

cursor.execute("""
        declare
            cust_cur sys_refcursor;
            sales_cur sys_refcursor;
        begin
            open cust_cur for SELECT * FROM cust_table;
            dbms_sql.return_result(cust_cur);

            open sales_cur for SELECT * FROM sales_table;
            dbms_sql.return_result(sales_cur);
        end;""")

for implicit_cursor in cursor.getimplicitresults():
    for row in implicit_cursor:
        print(row)

Data from both the result sets are returned:

(1, 'Tom')
(2, 'Julia')
(1000, 1, 'BOOKS')
(2000, 2, 'FURNITURE')

When using python-oracledb Thick mode, you must leave the parent cursor open until all of the implicit result sets have been fetched or until your application no longer requires them. Closing the parent cursor before fetching all of the implicit result sets will result in the closure of the implicit result set cursors. If you try to fetch from an implicit result set after its parent cursor is closed, the following error will be thrown:

DPI-1039: statement was already closed

Note that the requirement mentioned above is not applicable for python-oracledb Thin mode. See Implicit Results in Thin and Thick Modes.

7.9. Edition-Based Redefinition (EBR)

Oracle Database’s Edition-Based Redefinition feature enables upgrading of the database component of an application while it is in use, thereby minimizing or eliminating down time. This feature allows multiple versions of views, synonyms, PL/SQL objects and SQL Translation profiles to be used concurrently. Different versions of the database objects are associated with an “edition”.

The simplest way to set the edition used by your applications is to pass the edition parameter to oracledb.connect() or oracledb.create_pool():

connection = oracledb.connect(user="hr", password=userpwd,
                               dsn="dbhost.example.com/orclpdb",
                               edition="newsales")

The edition can also be set by executing the SQL statement:

alter session set edition = <edition name>;

You can also set the environment variable ORA_EDITION to your edition name.

Regardless of which method sets the edition, the value that is in use can be seen by examining the attribute Connection.edition. If no value has been set, the value will be None. This corresponds to the database default edition ORA$BASE.

Consider an example where one version of a PL/SQL function Discount is defined in the database default edition ORA$BASE and the other version of the same function is defined in a user created edition DEMO. In your SQL editor run:

connect <username>/<password>

-- create function using the database default edition
CREATE OR REPLACE FUNCTION Discount(price IN NUMBER) RETURN NUMBER IS
BEGIN
    return price * 0.9;
END;
/

A new edition named ‘DEMO’ is created and the user given permission to use editions. The use of FORCE is required if the user already contains one or more objects whose type is editionable and that also have non-editioned dependent objects.

connect system/<password>

CREATE EDITION demo;
ALTER USER <username> ENABLE EDITIONS FORCE;
GRANT USE ON EDITION demo to <username>;

The Discount function for the demo edition is as follows:

connect <username>/<password>

alter session set edition = demo;

-- Function for the demo edition
CREATE OR REPLACE FUNCTION Discount(price IN NUMBER) RETURN NUMBER IS
BEGIN
    return price * 0.5;
END;
/

A Python application can then call the required version of the PL/SQL function as shown:

connection = oracledb.connect(user=user, password=password,
                               dsn="dbhost.example.com/orclpdb")
print("Edition is:", repr(connection.edition))

cursor = connection.cursor()
discounted_price = cursor.callfunc("Discount", int, [100])
print("Price after discount is:", discounted_price)

# Use the edition parameter for the connection
connection = oracledb.connect(user=user, password=password,
                               dsn="dbhost.example.com/orclpdb",
                               edition="demo")
print("Edition is:", repr(connection.edition))

cursor = connection.cursor()
discounted_price = cursor.callfunc("Discount", int, [100])
print("Price after discount is:", discounted_price)

The output of the function call for the default and demo edition is as shown:

Edition is: None
Price after discount is:  90
Edition is: 'DEMO'
Price after discount is:  50