Useful PL/SQL Supplied Packages

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Useful Supplied
PL/SQL Packages
1
Maria Colgan
Master Product Manager
Oracle Database Server Technologies
June 2018
JEFF
@SQLMaria

DBMS_SESSION.SLEEP()
2
Accessible sleep function within PL/SQL
SQL> set timing on;
SQL> DECLARE
v_start date;
v_end date;
BEGIN
v_start := SYSDATE;
-- Sleep for 10 seconds
dbms_lock.sleep(10);
v_end := SYSDATE;
END;
/
PL/SQL procedure successfully
completed.
Elapsed: 00:00:10.02
• DBMS_LOCK includes other, more
sensitive methods
• Therefore not granted to public
• Requires DBA intervention to get a
accessible sleep function in PL/SQL

DBMS_SESSION.SLEEP()
3
Accessible sleep function within PL/SQL
SQL> set timing on;
SQL> DECLARE
v_start date;
v_end date;
BEGIN
v_start := SYSDATE;
-- Sleep for 10 seconds
DBMS_SESSION.SLEEP(10);
v_end := SYSDATE;
END;
/
PL/SQL procedure successfully
completed.
Elapsed: 00:00:10.02
• Doesn’t require GRANT anymore
– Before required explicit grant on
DBMS_LOCK
– DBMS_SESSION granted to public
• Compatible with DBMS_LOCK.SLEEP
– You can search/replace
• Introduced thanks to the Oracle
community
– https://community.oracle.com/ideas/4852

DBMS_UTILITY.EXPAND_SQL_TEXT
4
SELECT view_name
FROM user_views
WHERE view_name LIKE 'SALE%';
VIEW_NAME
-------------------
SALES_REPORTING2_V
SALES_REPORTING_V
Determining if this really is the right view to use
12c
• Views can be a useful way to hide
complexity from developers
• But they can also cause problems
• It's easy to write apparently simple
statements, that result in extremely
complex SQL being sent to the database
• The DBMS_UTILITY.EXPAND_SQL_TEXT
procedure expands references to views,
turning them into subqueries in the
original statement

set serveroutput on
DECLARE
l_clob CLOB;
BEGIN
dbms_utility.Expand_sql_text(
input_sql_text =>'SELECT * FROM SALES_REPORTING_V',
output_sql_text => l_clob);
dbms_output.Put_line(l_clob);
END;
/
5

SELECT "A1"."order_id" "ORDER_ID",
"A1"."time_id" "TIME_ID",
"A1"."cust_id" "CUST_ID",
"A1"."prod_id" "PROD_ID"
FROM (SELECT "A3"."order_id" "ORDER_ID",
FROM "SH"."sales" "A3",
"SH"."products" "A2"
WHERE "A3"."prod_id" = "A2"."prod_id") "A1"
6

set serveroutput on
DECLARE
l_clob CLOB;
BEGIN
dbms_utility.Expand_sql_text(
input_sql_text =>'SELECT * FROM SALES_REPORTING2_V',
output_sql_text => l_clob);
dbms_output.Put_line(l_clob);
END;
/
7

SELECT "A1"."order_id" "ORDER_ID",
FROM (SELECT "A2"."order_id" "ORDER_ID",
FROM "SH"."sales" "A2”) "A1"
8

DBMS_ADVANCED_REWRITE
9
Fixing the unfixable SQL statement
• You’ve been told you need to “fix” a
SQL statement that is no longer
returning results in the correct order
• But you can’t change the application
code directly as that would require
down time
• What do you do?
SQL> SELECT x, y, sum(z) FROM t
GROUP BY x, y;
X Y SUM(Z)
---------- ---------- ----------
1 4 110
2 3 84
10g
Something changes and now you get
GROUP BY x, y;
X Y SUM(Z)
---------- ---------- ----------
2 3 84
1 4 110

10
Step 1
• Check what changed with the
execution plan
ORIGINIAL PLAN
-----------------------------------
| Id | Operation | Name |
-----------------------------------
| 0 | SELECT STATEMENT | |
| 1 | HASH GROUP BY | |
| 2 | TABLE ACCESS FULL| T |
-----------------------------------
NEW PLAN
--------------------------------------
--------------------------------------
| 1 | SORT GROUP BY NOSORT| |
| 2 | INDEX FULL SCAN |T_IDX |
--------------------------------------

11
Step 2
• Check the order of the columns in the
index
SQL> SELECT column_position,
column_name
FROM user_ind_columns
WHERE index_name='T_IDX'
ORDER BY column_position;
COLUMN_POSITION COLUMN
--------------- ------
1 Y
2 X
3 Z
• New index returns the rows in a
different order because its sorted on
column Y rather than X

12
Step 3
• Create a view v that includes an order
by clause so the query results will
always be order based on the values
column x
SQL> CREATE OR REPLACE VIEW v
2 AS
3 SELECT x, y, sum(z) "SUM(Z)"
4 FROM t
5 GROUP BY x, y
6 ORDER BY x, y;
View created.

13
Step 4
• Use the DBMS_ADVANCED_REWRITE procedure to map the original query
to a simple SELECT * FROM v;
SQL> BEGIN
2 sys.dbms_advanced_rewrite.declare_rewrite_equivalence(
3 name => 'DEMO_TIME',
4 source_stmt => 'SELECT x, y, sum(z) FROM t GROUP BY x, y',
5 destination_stmt => 'SELECT * FROM v',
6 validate => FALSE,
7 rewrite_mode => 'TEXT_MATCH');
8 END;
9 /
PL/SQL procedure successfully completed.

14
• Each time our original SQL statement
is issued the
procedure rewrites it to be
SELECT * FROM v;
• Always get the query
output in an order list
GROUP BY x, y;
X Y SUM(Z)
---------- ---------- ----------
1 4 110
2 3 84
-----------------------------------
-----------------------------------
| 1 | VIEW | V |
| 2 | SORT GROUP BY | |
| 3 | INDEX FULL SCAN|T_IDX |
-----------------------------------

DBMS_COMPARISON
• Trying to figure out why things behave
differently in production then they do in
test can be time consuming and painful
• The DBMS_COMPARISON package allows
you to compare objects, schemas or data
between databases or schemas
• For a table comparison you do need a
unique index on both tables
• Begin by creating the comparison
15
Figuring out why production is different to test
SQL> BEGIN
DBMS_COMPARISON.CREATE_COMPARISON
(
comparison_name => 'COMP_SALES',
schema_name => 'SH',
object_name => 'SALES',
dblink_name => 'orcl2_test'
);
END;
/
11g

DBMS_COMPARISON
• Execute the
COMPARE function
to perform the
compare operation
• Returns a boolean to
say if there is or is not
consistency
• The scan_id allows
you to find out what
the differences are
16
SQL> DECLARE
scan_info DBMS_COMPARISON.COMPARISON_TYPE;
BEGIN
IF NOT DBMS_COMPARISON.COMPARE
( comparison_name => 'COMP_SALES'
, scan_info => scan_info
, perform_row_dif => TRUE
) THEN
DBMS_OUTPUT.PUT_LINE('Scan ID:'||
scan_info.scan_id);
END IF;
END;
/
Scan ID: 1

DBMS_COMPARISON
17
SELECT c.COLUMN_NAME, r.INDEX_VALUE,
case when r.LOCAL_ROWID is null then ‘No’ else 'Yes’ end LOCAL,
Case when r.REMOTE_ROWID is null then 'No’ else 'Yes’ end REMOTE
FROM USER_COMPARISON_COLUMNS c, USER_COMPARISON_ROW_DIF r,
USER_COMPARISON_SCAN s
WHERE c.COMPARISON_NAME = 'COMP_SALES‘
AND c.INDEX_COLUMN = 'Y’
AND r.STATUS = 'DIF’
AND c.COMPARISON_NAME = r.COMPARISON_NAME
AND r.SCAN_ID = s.SCAN_ID
AND s.SCAN_ID = 1
ORDER BY r.INDEX_VALUE;
COLUMN_NAME INDEX_VALUE LOCAL REMOTE
----------- ----------- ----- ------
TAX_CODE 0.05 No Yes
Test environment has an different tax code

Many More Powerful Supplied PL/SQL Packages
• Oracle Database 18c provides 300 PL/SQL packages
• Some of my favorites include:
– DBMS_STATS
– DBMS_SHARED_POOL
– DBMS_SPM
– DBMS_AUTO_TASK_ADMIN
– DBMS_SQLTUNE
• Check out more details in the PL/SQL Packages and Types Reference
18

Useful PL/SQL Supplied Packages

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