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Using CALIBRATE_IO

without comments

Using Oracle’s Resource Manager requires you to understand the IO dynamics. The first step requires you to run the CALIBRATE_IO procedure from the DBMS_RESOURCE_MANAGER package.

Oracle provides some great examples about how to use the CALIBRATE_IO procedure of the DBMS_RESOURCE_MANAGER package in the Oracle Database Database PL/SQL Packages and Types Reference. The CALIBRATE_IO procedure returns the best answer when you provide a valid number of files, which you can capture by querying the V$ASM_DISK view.

The following code queries the view and assigns the value to a session level variable:

CLEAR BREAKS
CLEAR COLUMNS
CLEAR COMPUTES
 
VARIABLE files NUMBER
 
BEGIN
  SELECT COUNT(DISTINCT name) disks
  INTO :files
  FROM v$asm_disk;
END;
/

When you have the number of files, you can calibrate the IO with the following anonymous block. The query should always work but just in case the NVL function on line 9 assigns the default number of files.

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DECLARE
  lv_num_physical_disks BINARY_INTEGER; — v$asm_disk
  lv_max_latency BINARY_INTEGER := 10;
  lv_max_iops BINARY_INTEGER;
  lv_max_mbps BINARY_INTEGER;
  lv_actual_latency BINARY_INTEGER;
BEGIN
  /* Assign actual files to anonymous block variable. */
  lv_num_physical_disks := NVL(:files,2);
 
  /* Run the calibrate_io procedure. */
  DBMS_RESOURCE_MANAGER.CALIBRATE_IO(
      num_physical_disks => lv_num_physical_disks
    , max_latency => lv_max_latency
    , max_iops => lv_max_iops
    , max_mbps => lv_max_mbps
    , actual_latency => lv_actual_latency);
END;
/

You can query the results like this:

SELECT max_iops
,      max_mbps
,      max_pmbps
,      latency
,      num_physical_disks
FROM   dba_rsrc_io_calibrate;

It should show results like these:

MAX_IOPS MAX_MBPS MAX_PMBPS LATENCY NUM_PHYSICAL_DISKS
-------- -------- --------- ------- ------------------
    8894      443       294       9                 18

Hope this helps those using the CALIBRATE_IO procedure of the DBMS_RESOURCE_MANAGER package.

Written by maclochlainn

August 31st, 2015 at 8:59 pm

Use an object in a query?

without comments

Using an Oracle object type’s instance in a query is a powerful capability. Unfortunately, Oracle’s SQL syntax doesn’t make it immediately obvious how to do it. Most get far enough to put it in a runtime view (a subquery in the FROM clause), but then they get errors like this:

SELECT	 instance.get_type()
         *
ERROR AT line 4:
ORA-00904: "INSTANCE"."GET_TYPE": invalid identifier

The problem is how Oracle treats runtime views, which appears to me as a casting error. Somewhat like the ORDER BY clause irregularity that I noted in July, the trick is complete versus incomplete syntax. The following query fails and generates the foregoing error:

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SELECT instance.get_type() AS object_type
,      instance.to_string() AS object_content
FROM  (SELECT dependent()AS instance
       FROM   dual);

If you add a table alias, or name, to the runtime view on line 4, it works fine:

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SELECT cte.instance.get_type() AS object_type
,      cte.instance.to_string() AS object_content
FROM  (SELECT dependent() AS instance
       FROM   dual) cte;

That is the trick. You use an alias for the query, which assigns the alias like a table reference. The reference lets you access instance methods in the scope of a query. Different columns in the query’s SELECT-list may return different results from different methods from the same instance of the object type.

You can also raise an exception if you forget the open and close parentheses for a method call to a UDT, which differs from how Oracle treats no argument functions and procedures. That type of error would look like this:

SELECT cte.instance.get_type AS object_type
       *
ERROR AT line 1:
ORA-00904: : invalid identifier

It is an invalid identifier because there’s no public variable get_type, and a method is only found by using the parenthesis and a list of parameters where they’re required.

The object source code is visible by clicking on the expandable label below.

As always, I hope this helps those solving problems.

Written by maclochlainn

August 22nd, 2015 at 5:23 pm

Oracle Cleanup a Schema

with one comment

Back in January 2014, I wrote a script to cleanup an Oracle student schema. It worked well until I started using APEX 4 in my student schema. You create the following 75 objects when you create an APEX 4 schema.

OBJECT TYPE    TOTAL
------------ -------
TABLE		  17
INDEX		  28
SEQUENCE	   5
TRIGGER 	  14
LOB		   9
FUNCTION	   2

Here’s the modified script that ignores the objects created automatically by Oracle APEX when you create a student workspace:

BEGIN
  FOR i IN (SELECT    object_name
            ,         object_type
            ,         last_ddl_time
            FROM      user_objects
            WHERE     object_name NOT IN
                       ('APEX$_WS_WEBPG_SECTION_HISTORY','APEX$_WS_WEBPG_SECTIONS_T1'
                       ,'APEX$_WS_WEBPG_SECTIONS_PK','APEX$_WS_WEBPG_SECTIONS'
                       ,'APEX$_WS_WEBPG_SECHIST_IDX1','APEX$_WS_TAGS_T1'
                       ,'APEX$_WS_TAGS_PK','APEX$_WS_TAGS_IDX2','APEX$_WS_TAGS_IDX1'
                       ,'APEX$_WS_TAGS','APEX$_WS_ROWS_T1','APEX$_WS_ROWS_PK'
                       ,'APEX$_WS_ROWS_IDX','APEX$_WS_ROWS','APEX$_WS_NOTES_T1'
                       ,'APEX$_WS_NOTES_PK','APEX$_WS_NOTES_IDX2','APEX$_WS_NOTES_IDX1'
                       ,'APEX$_WS_NOTES','APEX$_WS_LINKS_T1','APEX$_WS_LINKS_PK'
                       ,'APEX$_WS_LINKS_IDX2','APEX$_WS_LINKS_IDX1','APEX$_WS_LINKS'
                       ,'APEX$_WS_HISTORY_IDX','APEX$_WS_HISTORY','APEX$_WS_FILES_T1'
                       ,'APEX$_WS_FILES_PK','APEX$_WS_FILES_IDX2','APEX$_WS_FILES_IDX1'
                       ,'APEX$_WS_FILES','APEX$_ACL_T1','APEX$_ACL_PK','APEX$_ACL_IDX1'
                       ,'APEX$_ACL','CUSTOM_AUTH','CUSTOM_HASH','DEPT','EMP'
                       ,'UPDATE_ORDER_TOTAL')
            AND NOT ((object_name LIKE 'DEMO%' OR
                      object_name LIKE 'INSERT_DEMO%' OR
                      object_name LIKE 'BI_DEMO%') AND
                      object_type IN ('TABLE','INDEX','SEQUENCE','TRIGGER'))
            AND NOT (object_name LIKE 'SYS_LOB%' AND object_type = 'LOB')
            AND NOT (object_name LIKE 'SYS_C%' AND object_type = 'INDEX')
            ORDER BY object_type DESC) LOOP
 
    /* Drop types in descending order. */
    IF i.object_type = 'TYPE' THEN
 
      /* Drop type and force operation because dependencies may exist. Oracle 12c
         also fails to remove object types with dependents in pluggable databases
         (at least in release 12.1). Type evolution works in container database
         schemas. */
      EXECUTE IMMEDIATE 'DROP '||i.object_type||' '||i.object_name||' FORCE';
 
    /* Drop table tables in descending order. */
    ELSIF i.object_type = 'TABLE' THEN
 
      /* Drop table with cascading constraints to ensure foreign key constraints
         don't prevent the action. */
      EXECUTE IMMEDIATE 'DROP '||i.object_type||' '||i.object_name||' CASCADE CONSTRAINTS PURGE';
 
      /* Oracle 12c ONLY: Purge the recyclebin to dispose of system-generated
         sequence values because dropping the table doesn't automatically 
         remove them from the active session.
         CRITICAL: Remark out the following when working in Oracle Database 11g. */
      EXECUTE IMMEDIATE 'PURGE RECYCLEBIN';
 
    ELSIF i.object_type = 'LOB' OR i.object_type = 'INDEX' THEN
 
      /* A system generated LOB column or INDEX will cause a failure in a
         generic drop of a table because it is listed in the cursor but removed
         by the drop of its table. This NULL block ensures there is no attempt
         to drop an implicit LOB data type or index because the dropping the
         table takes care of it. */
      NULL;
 
    ELSE
 
      dbms_output.put_line('DROP '||i.object_type||' '||i.object_name||';');
      /* Drop any other objects, like sequences, functions, procedures, and packages. */
      EXECUTE IMMEDIATE 'DROP '||i.object_type||' '||i.object_name;
 
    END IF;
  END LOOP;
END;
/

As always, I hope this helps others.

Written by maclochlainn

April 19th, 2015 at 7:13 pm

Functions disallow NDS

with 2 comments

My students asked if you could embed an OFFSET x ROWS FETCH NEXT y ROWS ONLY clause in a SQL Server T-SQL user-defined function. The answer is no, it isn’t Oracle (yes, you can do that in Oracle Database 12c with an NDS statement). There’s an example in Chapter 2 of my Oracle Database 12c PL/SQL Programming book if you’re interested. I also demonstrate a different approach to SQL Server T-SQL table functions in this older post. However, an attempt to add the clause to a SQL Server T-SQL function, like this:

CREATE FUNCTION studentdb.getBatch
(@rows   AS INT
,@offset AS INT) RETURNS @output TABLE
( marvel_id    INT 
, avenger_name VARCHAR(30)
, first_name   VARCHAR(20)
, last_name    VARCHAR(20)) AS
BEGIN
  /* Insert the results into the table variable. */
  INSERT @output
  SELECT marvel_id
  ,      avenger_name
  ,      first_name
	,      last_name
  FROM   studentdb.marvel
  OFFSET (@offset - 1) ROWS FETCH NEXT @rows ROWS ONLY;
 
  /* Return the table variable from the function. */  
  RETURN;
END;

Throws the following errors trying to compile the function:

Msg 102, Level 15, State 1, Procedure getBatch, Line 16
Incorrect syntax near '@offset'.
Msg 153, Level 15, State 2, Procedure getBatch, Line 16
Invalid usage of the option NEXT in the FETCH statement.

If you have a strong background in Oracle and can sort through the dynamic SQL syntax for T-SQL, you might try re-writing the function to use the EXEC SP_EXECUTESQL @var; command. That rewrite that attempts to use NDS (Native Dynamic SQL) would look like this:

CREATE FUNCTION studentdb.getBatch
(@rows   AS INT
,@offset AS INT) RETURNS @output TABLE
( marvel_id    INT 
, avenger_name VARCHAR(30)
, first_name   VARCHAR(20)
, last_name    VARCHAR(20)) AS
BEGIN
  DECLARE
    /* Declare a variable for a dynamic SQL statement. */
    @stmt          VARCHAR(400);
 
    /* Assign the SQL statement to a variable. */
    SET @stmt = N'SELECT marvel_id ' +
                N',      avenger_name ' +
                N',      first_name ' +
                N',      last_name ' +
                N'FROM   studentdb.marvel ' +
                N'OFFSET ' + (@offset - 1) + N' ' +
                N'ROWS FETCH NEXT ' + @rows + N' ROWS ONLY;';
  BEGIN
    /* Insert the results into the table variable. */
    INSERT @output
    EXEC sp_executesql @stmt; 
  END;
 
  /* Return the table variable from the function. */  
  RETURN;
END;

Throws the following exception because you can’t use dynamic dispatch inside a T-SQL function:

Msg 443, Level 16, State 14, Procedure getBatch, Line 23
Invalid use of a side-effecting operator 'INSERT EXEC' within a function.

On the other hand you can rewrite the statement with a BETWEEN operator and it works somewhat like an OFFSET and FETCH operation. That refactored function would be written as follows:

CREATE FUNCTION studentdb.getBatch
(@rowa  AS INT
,@rowb AS INT) RETURNS @output TABLE
( marvel_id    INT 
, avenger_name VARCHAR(30)
, first_name   VARCHAR(20)
, last_name    VARCHAR(20)) AS
BEGIN
  /* Insert the results into the table variable. */
  INSERT @output
  SELECT marvel_id
  ,      avenger_name
  ,      first_name
  ,      last_name
  FROM   studentdb.marvel
  WHERE  marvel_id BETWEEN @rowa AND @rowb;
 
  /* Return the table variable from the function. */  
  RETURN;
END;

It doesn’t raise an exception. You can call the table function like this:

SELECT * FROM getBatch(2,3);

It returns the two rows for Iron Man and Black Widow. As always, I hope this helps.

If you want to create the test case, here’s the script you need:

SELECT 'Conditionally drop studentdb.marvel table.' AS "Statement";
IF OBJECT_ID('studentdb.marvel','U') IS NOT NULL
  DROP TABLE studentdb.marvel;
 
SELECT 'Create studentdb.marvel table.' AS "Statement";
CREATE TABLE studentdb.marvel
( marvel_id     INT          NOT NULL IDENTITY(1,1) CONSTRAINT marvel_pk PRIMARY KEY
, avenger_name  VARCHAR(30)  NOT NULL
, first_name    VARCHAR(20)  NOT NULL
, last_name     VARCHAR(20)  NOT NULL);
 
/* Insert the rows. */
INSERT INTO studentdb.marvel (avenger_name, first_name, last_name) VALUES ('Hulk','Bruce','Banner');
INSERT INTO studentdb.marvel (avenger_name, first_name, last_name) VALUES ('Iron Man','Tony','Stark');
INSERT INTO studentdb.marvel (avenger_name, first_name, last_name) VALUES ('Black Widow','Natasha','Romanoff');
INSERT INTO studentdb.marvel (avenger_name, first_name, last_name) VALUES ('Thor','Thor','Odinsson');
INSERT INTO studentdb.marvel (avenger_name, first_name, last_name) VALUES ('Captain America','Steve','Rogers');
INSERT INTO studentdb.marvel (avenger_name, first_name, last_name) VALUES ('Hawkeye','Clint','Barton');
INSERT INTO studentdb.marvel (avenger_name, first_name, last_name) VALUES ('Winter Soldier','Bucky','Barnes');
INSERT INTO studentdb.marvel (avenger_name, first_name, last_name) VALUES ('Iron Patriot','James','Rhodey');
 
/* Query the contents of the MARVEL table. */
SELECT * FROM studentdb.marvel;

Written by maclochlainn

February 14th, 2015 at 5:20 pm

Filtering String Dates

without comments

A question came up about how to verify dates from a string without throwing a casting error because of a non-conforming date. You can throw a number of exceptions, and I wrote a function to filter bad string formats like the DD-MON-RR or DD-MON-YYYY.

The first one is for a day between 1 and the last day of month, which is:

ORA-01847: day of month must be between 1 and last day of month

An incorrect string for a month, raises the following error:

ORA-01843: not a valid month

A date format mask longer than a DD-MON-RR or DD-MON-YYYY raises the following exception:

ORA-01830: date format picture ends before converting entire input string

The verify_date function checks for non-conforming DD-MON-RR and DD-MON-YYYY date masks, and substitutes a SYSDATE value for a bad date entry:

CREATE OR REPLACE
  FUNCTION verify_date
  ( pv_date_in  VARCHAR2) RETURN DATE IS
  /* Local return variable. */
  lv_date  DATE;
BEGIN
  /* Check for a DD-MON-RR or DD-MON-YYYY string. */
  IF REGEXP_LIKE(pv_date_in,'^[0-9]{2,}-[ADFJMNOS][ACEOPU][BCGLNPRTVY]-([0-9]{2,}|[0-9]{4,})$') THEN
    /* Case statement checks for 28 or 29, 30, or 31 day month. */
    CASE
      /* Valid 31 day month date value. */
      WHEN SUBSTR(pv_date_in,4,3) IN ('JAN','MAR','MAY','JUL','AUG','OCT','DEC') AND
           TO_NUMBER(SUBSTR(pv_date_in,1,2)) BETWEEN 1 AND 31 THEN 
        lv_date := pv_date_in;
      /* Valid 30 day month date value. */
      WHEN SUBSTR(pv_date_in,4,3) IN ('APR','JUN','SEP','NOV') AND
           TO_NUMBER(SUBSTR(pv_date_in,1,2)) BETWEEN 1 AND 30 THEN 
        lv_date := pv_date_in;
      /* Valid 28 or 29 day month date value. */
      WHEN SUBSTR(pv_date_in,4,3) = 'FEB' THEN
        /* Verify 2-digit or 4-digit year. */
        IF (LENGTH(pv_date_in) = 9 AND MOD(TO_NUMBER(SUBSTR(pv_date_in,8,2)) + 2000,4) = 0 OR
            LENGTH(pv_date_in) = 11 AND MOD(TO_NUMBER(SUBSTR(pv_date_in,8,4)),4) = 0) AND
            TO_NUMBER(SUBSTR(pv_date_in,1,2)) BETWEEN 1 AND 29 THEN
          lv_date := pv_date_in;
        ELSE /* Not a leap year. */
          IF TO_NUMBER(SUBSTR(pv_date_in,1,2)) BETWEEN 1 AND 28 THEN
            lv_date := pv_date_in;
          ELSE
            lv_date := SYSDATE;
          END IF;
        END IF;
      ELSE
        /* Assign a default date. */
        lv_date := SYSDATE;
    END CASE;
  ELSE
    /* Assign a default date. */
    lv_date := SYSDATE;
  END IF;
  /* Return date. */
  RETURN lv_date;
END;
/

You can check valid dates with a DD-MON-RR format:

SELECT verify_date('28-FEB-10') AS "Non-Leap Year"
,      verify_date('29-FEB-12') AS "Leap Year"
,      verify_date('31-MAR-14') AS "31-Day Year"
,      verify_date('30-APR-14') AS "30-Day Year"
FROM   dual;

You can check valid dates with a DD-MON-YYYY format:

SELECT verify_date('28-FEB-2010') AS "Non-Leap Year"
,      verify_date('29-FEB-2012') AS "Leap Year"
,      verify_date('31-MAR-2014') AS "31-Day Year"
,      verify_date('30-APR-2014') AS "30-Day Year"
FROM   dual;

They both return:

Non-Leap    Leap YEAR 31-DAY YEAR 30-DAY YEAR
----------- --------- ----------- -----------
28-FEB-10   29-FEB-12 31-MAR-14   30-APR-14

You can check badly formatted dates with the following query:

SELECT verify_date('28-FEB-2010') AS "Non-Leap Year"
,      verify_date('29-FEB-2012') AS "Leap Year"
,      verify_date('31-MAR-2014') AS "31-Day Year"
,      verify_date('30-APR-2014') AS "30-Day Year"
FROM   dual;

You can screen for an alphanumeric string with the following expression:

SELECT 'Valid alphanumeric string literal' AS "Statement"
FROM   dual
WHERE  REGEXP_LIKE('Some Mythical String $200','([:alnum:]|[:punct:]|[:space:])*');

You can screen for a numeric literal as a string with the following expression:

SELECT 'Valid numeric literal' AS "Statement"
FROM   dual
WHERE  REGEXP_LIKE('123.00','([:digit:]|[:punct:])');

As always, I hope this helps those who need this type of solution.

Written by maclochlainn

February 2nd, 2015 at 12:53 am

PL/SQL Fall Through?

with 2 comments

Somebody wants to know how you can write a PL/SQL solution that mimics the fall through of a switch statement because PL/SQL doesn’t support a switch statement (it does support a simple and searched CASE statement without fall through). It’s a question that I found interesting because there wasn’t a need for it when I figured out what he wanted to accomplish. Essentially, he wanted to know how to implement a nested loop where the first loop runs in ascending order and the nested loop runs in descending order based on the value of the outer loop.

While it seems Christmas songs aren’t politically correct, The Twelve Days of Christmas lets me show you how to implement a coupled nested loop. The easiest way to implement a solution requires an object type, like

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CREATE OR REPLACE
  TYPE lyric IS OBJECT
  ( day_name   VARCHAR2(8)
  , gift_name  VARCHAR2(24));
/

The following anonymous block program shows you how to couple the performance of nested loops to print the lyrics from two collections:

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DECLARE
  /* Declare an array of days and gifts. */
  TYPE days IS TABLE OF VARCHAR2(8);
  TYPE gifts IS TABLE OF lyric;
 
  /* Initialize the collection of days. */                    
  lv_days DAYS := days( 'first', 'second', 'third', 'fourth'
                      , 'fifth', 'sixth', 'seventh', 'eighth'
                      , 'nineth', 'tenth', 'eleventh', 'twelfth');
 
  /* Initialize the collection of lyrics. */
  lv_gifts GIFTS := gifts( lyric('and a', 'Partridge in a Pear Tree')
                         , lyric('Two', 'Turtle Doves')
                         , lyric('Three', 'French Hens')
                         , lyric('Four', 'Calling Birds')
                         , lyric('Five', 'Golden Rings' )
                         , lyric('Six', 'Geese a Laying')
                         , lyric('Seven', 'Swans a Swimming')
                         , lyric('Eight', 'Maids a Milking')
                         , lyric('Nine', 'Maids a Milking')
                         , lyric('Ten', 'Lords a Leaping')
                         , lyric('Eleven', 'Pipers Piping')
                         , lyric('Twelve', 'Drummers Drumming'));
BEGIN
  /* Read forward through the days. */
  FOR i IN 1..lv_days.COUNT LOOP
    DBMS_OUTPUT.put_line('On the ' || lv_days(i) || ' day of Christmas');
    DBMS_OUTPUT.put_line('my true love sent to me:');
 
    /* Read backward through the lyrics based on the ascending value of the day. */   
    FOR j IN REVERSE 1..i LOOP
      IF i = 1 THEN
        DBMS_OUTPUT.put_line('-'||'A'||' '||lv_gifts(j).gift_name);
      ELSE
        DBMS_OUTPUT.put_line('-'||lv_gifts(j).day_name||' '||lv_gifts(j).gift_name);
      END IF;
    END LOOP;
 
    /* A line break by verse. */
    DBMS_OUTPUT.put_line(CHR(10));
  END LOOP; 
END;
/

The FOR loop on line 31 descends from the current index of the ascending out loop. This shows you how to couple the performance of outer and inner loops. It let’s you print The Twelve Days of Christmas, as:

On the first day of Christmas
my true love sent to me:
-A Partridge in a Pear Tree
 
 
On the second day of Christmas
my true love sent to me:
-Two Turtle Doves
-and a Partridge in a Pear Tree
 
 
On the third day of Christmas
my true love sent to me:
-Three French Hens
-Two Turtle Doves
-and a Partridge in a Pear Tree
 
 
On the fourth day of Christmas
my true love sent to me:
-Four Calling Birds
-Three French Hens
-Two Turtle Doves
-and a Partridge in a Pear Tree
 
 
On the fifth day of Christmas
my true love sent to me:
-Five Golden Rings
-Four Calling Birds
-Three French Hens
-Two Turtle Doves
-and a Partridge in a Pear Tree
 
 
On the sixth day of Christmas
my true love sent to me:
-Six Geese a Laying
-Five Golden Rings
-Four Calling Birds
-Three French Hens
-Two Turtle Doves
-and a Partridge in a Pear Tree
 
 
On the seventh day of Christmas
my true love sent to me:
-Seven Swans a Swimming
-Six Geese a Laying
-Five Golden Rings
-Four Calling Birds
-Three French Hens
-Two Turtle Doves
-and a Partridge in a Pear Tree
 
 
On the eighth day of Christmas
my true love sent to me:
-Eight Maids a Milking
-Seven Swans a Swimming
-Six Geese a Laying
-Five Golden Rings
-Four Calling Birds
-Three French Hens
-Two Turtle Doves
-and a Partridge in a Pear Tree
 
 
On the nineth day of Christmas
my true love sent to me:
-Nine Maids a Milking
-Eight Maids a Milking
-Seven Swans a Swimming
-Six Geese a Laying
-Five Golden Rings
-Four Calling Birds
-Three French Hens
-Two Turtle Doves
-and a Partridge in a Pear Tree
 
 
On the tenth day of Christmas
my true love sent to me:
-Ten Lords a Leaping
-Nine Maids a Milking
-Eight Maids a Milking
-Seven Swans a Swimming
-Six Geese a Laying
-Five Golden Rings
-Four Calling Birds
-Three French Hens
-Two Turtle Doves
-and a Partridge in a Pear Tree
 
 
On the eleventh day of Christmas
my true love sent to me:
-Eleven Pipers Piping
-Ten Lords a Leaping
-Nine Maids a Milking
-Eight Maids a Milking
-Seven Swans a Swimming
-Six Geese a Laying
-Five Golden Rings
-Four Calling Birds
-Three French Hens
-Two Turtle Doves
-and a Partridge in a Pear Tree
 
 
On the twelfth day of Christmas
my true love sent to me:
-Twelve Drummers Drumming
-Eleven Pipers Piping
-Ten Lords a Leaping
-Nine Maids a Milking
-Eight Maids a Milking
-Seven Swans a Swimming
-Six Geese a Laying
-Five Golden Rings
-Four Calling Birds
-Three French Hens
-Two Turtle Doves
-and a Partridge in a Pear Tree

My conclusion is that the PL/SQL language doesn’t need to support fall through because it provides a simpler and more effective solution with coupled nested loops. As always, I hope the example helps those interested in a solution.

Written by maclochlainn

January 18th, 2015 at 12:13 am

Querying an Object Type

without comments

I demonstrated a number of SQL approaches to reading object types in Appendix B of the Oracle Database 12c PL/SQL Programming book. For example, the easiest one to construct and return the results from a TO_STRING member function uses the TREAT function:

SELECT TREAT(base_t() AS base_t).to_string() AS "Text"
FROM   dual;

However, it seems that I could have provided one more. Here’s an example of how you can test the construction of an object type and how you can return its attributes with a query. It’s important to note that there’s a natural problem with this syntax when you increment a sequence inside the object type. The problem is that it double increments the counter for the sequence.

SELECT *
FROM   TABLE(SELECT CAST(COLLECT(base_t()) AS base_t_tab)
             FROM dual);

The syntax for the COLLECT function requires that you put it inside a SELECT-list. Then, the CAST function converts a single instance of the BASE_T object type to a one element BASE_T_TAB collection. Finally, the TABLE function returns a single row from the BASE_T_TAB collection.

You can find a more complete article covering column substitutability and object types and subtypes on the ToadWorld site. I think it helps clear up how you can effectively write PL/SQL types and subtypes for persistent object type columns.

Written by maclochlainn

November 25th, 2014 at 12:33 am

Finding Direct Indexes

without comments

If you’re not using Toad DBA Suite, it’s sometimes hard to find solutions. Somebody wanted to know how to find indexes that aren’t indirect. Indirect indexes are those created for a primary key because a primary key column or set of columns are both not null and uniquely constrained. Likewise, you create a unique index when you can create a unique constraint. You can’t drop a unique index for a primary key without dropping the primary key or unique constraint that indirectly created it.

The following query returns indexes with one or more columns that are created by a CREATE INDEX statement on a target table. It excludes unique indexes created by a primary key constraint, and it returns the relative position of columns in an index:

COLUMN sequence_name   FORMAT A22 HEADING "Sequence Name"
COLUMN column_position FORMAT 999 HEADING "Column|Position"
COLUMN column_name     FORMAT A22 HEADING "Column|Name"
SELECT   uin.index_name
,        uic.column_position
,        uic.column_name
FROM     user_indexes uin INNER JOIN user_ind_columns uic
ON       uin.index_name = uic.index_name
AND      uin.table_name = uic.table_name
WHERE    uin.table_name = UPPER('&&table_name')
AND NOT  uin.index_name IN (SELECT constraint_name
                            FROM   user_constraints
                            WHERE  table_name = UPPER('&&table_name'))
ORDER BY uin.index_name
,        uic.column_position;

It can be rewritten into a function, which can then drop indexes based on a table name:

CREATE OR REPLACE FUNCTION drop_indexes_on
( pv_table_name  VARCHAR2 ) RETURN NUMBER IS 
 
  /* A return value. */
  lv_return  NUMBER := 0;
 
  /* A query to return only directly created indexes. */
  CURSOR find_indexes_on
  ( cv_table_name  VARCHAR2 ) IS
    SELECT   DISTINCT ui.index_name
    FROM     user_indexes ui INNER JOIN user_ind_columns uic
    ON       ui.index_name = uic.index_name
    AND      ui.table_name = uic.table_name
    WHERE    ui.table_name = UPPER(cv_table_name)
    AND NOT  ui.index_name IN (SELECT constraint_name
                               FROM   user_constraints
                               WHERE  table_name = UPPER(cv_table_name));
 
  /* Declare function autonomous. */
  PRAGMA AUTONOMOUS_TRANSACTION;
 
BEGIN
 
  /* Drop the indexes on a table. */
  FOR i IN find_indexes_on(pv_table_name) LOOP
    EXECUTE IMMEDIATE 'DROP INDEX '||i.index_name;
    lv_return := 1;
  END LOOP;
 
  RETURN lv_return;
END drop_indexes_on;
/

You can call the drop_on_indexes_on function like this:

SELECT   drop_indexes_on(UPPER('address_lab'))
FROM     dual;

Hope this helps those who need to work with dropping indexes.

Written by maclochlainn

November 23rd, 2014 at 8:42 pm

Parsing DBMS_OUTPUT

without comments

Testing with DBMS_OUTPUT.PUT_LINE is always a bit of a problem when you have strings longer than 80 characters in length, which occurs more frequently with Oracle Database 12c. An example of managing output occurs when you want to print a string with embedded line breaks. My solution is the following parse_rows procedure:

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CREATE OR REPLACE PROCEDURE parse_rows
( pv_text  VARCHAR2 ) IS
 
  /* Declare parsing indexes. */
  lv_start     NUMBER := 1;
  lv_end       NUMBER := 1;
  lv_length    NUMBER;
 
BEGIN
 
  /* Assign an end value based on parsing line return or length. */
  IF INSTR(pv_text,CHR(10),lv_start) = 0 THEN
    lv_end := LENGTH(pv_text) + 1;
  ELSE
    lv_end := INSTR(pv_text,CHR(10),lv_start);
  END IF;
 
  /* Assign a length value to the parsed string. */
  lv_length := lv_end - lv_start;
 
  /* Print first line. */
  DBMS_OUTPUT.put_line(SUBSTR(pv_text,lv_start,lv_length));
 
  /* Print the rows of a multiple line string. */
  WHILE (lv_end < LENGTH(pv_text)) LOOP
 
    /* Assign a new start value. */
    lv_start := lv_end + 1;
 
    /* Assign a new end value. */
    IF INSTR(pv_text,CHR(10),lv_start + 1) = 0 THEN
      lv_end := LENGTH(pv_text) + 1;
    ELSE
      lv_end := INSTR(pv_text,CHR(10),lv_start + 1);
    END IF;
 
    /* Assign a new length. */
    lv_length := lv_end - lv_start;
 
    /* Print the individual rows. */
    DBMS_OUTPUT.put_line(SUBSTR(pv_text,lv_start,lv_length));
 
  END LOOP;
END;
/

Here’s the example of a test program for the procedure:

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DECLARE
  /* Declare text. */
  lv_text  VARCHAR2(200) := 'This is too much'||CHR(10)||'information'||CHR(10)||'on one line.';
BEGIN
  parse_rows(lv_text);
END;
/

It prints the following:

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This is too much
information
on one line.

Hope this benefits those looking for quick solution.

Written by maclochlainn

May 21st, 2014 at 12:35 am

Oracle 12c VARCHAR2?

without comments

The Oracle Database 12c documentation says you can set the maximum size of a VARCHAR2 to 32,767 bytes. That’s true except when you’re trying to map a large Java string to a VARCHAR2. It fails when the physical size of the Java string is greater than 4,000 bytes with an ORA-01002 or fetch out of sequence error.

SELECT read_text_file('C:\Data\loader\Hobbit1.txt')
*
ERROR at line 1:
ORA-24345: A Truncation or null fetch error occurred
 
ERROR:
ORA-01002: fetch out of sequence

You need to grant privileges before you can test this code. You can grant privileges by connecting as the SYS user of a CDB (or non-multitenant database) or as the ADMIN user of a PDB with the AS SYSDBA clause. Then, you run the following command to grant external file access to the JVM inside Oracle Database 12c:

BEGIN
  DBMS_JAVA.GRANT_PERMISSION('IMPORTER'
                            ,'SYS:java.io.FilePermission'
                            ,'C:\Data\Loader\Hobbit1.txt'
                            ,'read');
END;
/

The IMPORTER is a PDB user name, or a non-multitenant database user name. Please note that permissions must be granted on each physical file.

Here’s the code that raises the error when the external file is greater than 4,000 bytes:

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CREATE OR REPLACE AND COMPILE JAVA SOURCE NAMED "ReadFile" AS
  // Java library imports.
  import java.io.File;
  import java.io.BufferedReader;
  import java.io.FileNotFoundException;
  import java.io.IOException;
  import java.io.FileReader;
  import java.security.AccessControlException;
 
  // Class definition.  
  public class ReadFile {
    // Define class variables.
    private static File file;
    private static FileReader inTextFile;
    private static BufferedReader inTextReader;
    private static StringBuffer output = new StringBuffer();
    private static String outLine, outText;
 
    // Define readText() method.
    public static String readText(String fromFile)
      throws AccessControlException, IOException {
      // Read file.
      try {
        // Initialize File.
        file = new File(fromFile);
 
        // Check for valid file.
        if (file.exists()) {
 
          // Assign file to a stream.          
          inTextFile = new FileReader(file);
          inTextReader = new BufferedReader(inTextFile);
 
          // Read character-by-character.
          while ((outLine = inTextReader.readLine()) != null) {
            output.append(outLine + "\n"); }
 
          // Assing the StringBuffer to a String.
          outText = output.toString();
 
          // Close File.
          inTextFile.close(); }
        else {
          outText = new String("Empty"); }}
      catch (IOException e) {
        outText = new String("");
        return outText; }
    return outText; }}
/

The PL/SQL wrapper should look like this:

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CREATE OR REPLACE FUNCTION read_text_file
(from_file VARCHAR2) RETURN VARCHAR2 IS
LANGUAGE JAVA
NAME 'ReadFile.readText(java.lang.String) return java.lang.String';
/

Then, you can query it like so:

SELECT read_text_file('C:\Data\loader\Hobbit1.txt')
FROM dual;

You can avoid the error by returning the Java file size as a CLOB data type with the following Java source code.

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CREATE OR REPLACE AND COMPILE JAVA SOURCE NAMED "ReadFile" AS
  // Java library imports.
  import java.io.File;
  import java.io.BufferedReader;
  import java.io.FileNotFoundException;
  import java.io.IOException;
  import java.io.FileReader;
  import java.security.AccessControlException;
  import java.sql.*;
  import oracle.sql.driver.*;
  import oracle.sql.*;
 
  // Class definition.  
  public class ReadFile {
    // Define class variables.
    private static int i;
    private static File file;
    private static FileReader inTextFile;
    private static BufferedReader inTextReader;
    private static StringBuffer output = new StringBuffer();
    private static String outLine, outText;
    private static CLOB outCLOB;
 
    // Define readText() method.
    public static oracle.sql.CLOB readText(String fromFile)
      throws AccessControlException, IOException, SQLException  {
      // Read file.
      try {
        // Initialize File.
        file = new File(fromFile);
 
        // Check for valid file.
        if (file.exists()) {
 
          // Assign file to a stream.          
          inTextFile = new FileReader(file);
          inTextReader = new BufferedReader(inTextFile);
 
          // Read character-by-character.
          while ((outLine = inTextReader.readLine()) != null) {
            output.append(outLine + "\n"); }
 
          // Assing the StringBuffer to a String.
          outText = output.toString();
 
          // Declare an Oracle connection.
          Connection conn = DriverManager.getConnection("jdbc:default:connection:");
 
          // Transfer the String to CLOB.
          outCLOB = CLOB.createTemporary((oracle.jdbc.OracleConnectionWrapper) conn, true, CLOB.DURATION_SESSION);
          i = outCLOB.setString(1,outText);
 
          // Close File.
          inTextFile.close(); }
        else {
          i = outCLOB.setString(1,"Empty"); }}
      catch (IOException e) {
        i = outCLOB.setString(1,"");
        return outCLOB; }
    return outCLOB; }}
/

The wrapper changes to return a CLOB and map a java.sql.CLOB as the return type of the Java library. This command works:

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CREATE OR REPLACE FUNCTION read_clob_file
(from_file VARCHAR2) RETURN CLOB IS
LANGUAGE JAVA
NAME 'ReadFile.readText(java.lang.String) return oracle.sql.CLOB';
/

You now query the PL/SQL wrapper with this type of effective SQL*Plus command-line command:

COLUMN atext FORMAT A60 HEADING "Text"
COLUMN asize FORMAT 99,999 HEADING "Size"
 
SELECT   read_clob_file('C:\Data\loader\Hobbit1.txt') AS AText
,        LENGTH(read_clob_file('C:\Data\loader\Hobbit1.txt')) AS ASize
FROM dual;

As always, I hope this helps somebody.

Written by maclochlainn

May 7th, 2014 at 3:03 am