What a news! Oracle Buys Sun !

Written by Paweł Barut
What a news: Oracle Buys Sun !! I'm not the first one that blogs about it, but anyway let me express my comments. What does it mean for IT:
1. Oracle software will be installed on almost every PC; Sun Java might be renamed to Oracle Java. It will give wider recognition for Oracle trademark also to people that are not so much engaged with IT Industry.
2. Oracle becomes hardware producer. Well, you might know already HP-Oracle Database Machine (Exadata), but this was joint-venture. Now Oracle will produce hardware and software that runs on it. If everything goes right next "Database Machine" will be fully "Oracle".
3. Sun Solaris is #1 platform for running Oracle, and the second one is Linux. This could mean that rate for Linux implementation in enterprises will be lower, as many companies would choose OS and DB from one vendor. I know that Oracle is also offering Linux, but Oracle sales will be promoting Solaris, as this deals will be better for Oracle.
4. Oracle now owns 2, ehh, 3 databases: Oracle, Berkley XML DB and now MySQL. I could mean that MySQL will get even bettor, or rather it will mean that Oracle will offer MySQL customer to migrate to Oracle. So far Oracle does not have good record for supporting free editions of Databases. We will see...
5. With Oracle-Sun merge, Oracle will be shipping now full stack: hardware,OS, Database, Midlleware, ERM, CRM and many others. Oracle is becoming giant now...

Read also what others have to say:

• Mark Rittman - Oracle Buys Sun - What Does It Mean for Oracle BI&DW?
• Pythian - Oracle Buys Sun
  
• Marco Gralike - Oracle to buy Sun, Ehh MySQL, Ehh Glashfish…
• Tanel Poder - Oracle buys Sun - hooray!
  
• Tim Hall - Oracle Buy Sun Microsystems…
  
• Kevin Closson - Everyone Else is Doing It!
  
• Jaffar - Oracle to acquire SUN?

Keep reading,
Paweł

Caution: FOR loop and CONTINUE in Oracle 11g

Written by Paweł Barut
Friend of mine showed me interesting issue of using CONTINUE Statement. CONTINUE is an new statement in Oracle 11; it allow to skip processing of current iteration of look, and go to begging of next iteration. So here is working sample:

SQL> set serveroutput on
SQL> begin
  2    dbms_output.put_line('=== START');
  3    for i in 1..15 loop
  4      dbms_output.put_line('before:'||i);
  5      if mod(i, 5) = 0 then
  6        dbms_output.put_line('CONTINUE');
  7        continue;
  8      end if;
  9      dbms_output.put_line('after:'||i);
 10    end loop;
 11    dbms_output.put_line('=== STOP');
 12  end;
 13  /
=== START
before:1
after:1
before:2
after:2
before:3
after:3
before:4
after:4
before:5
CONTINUE
before:6
after:6
before:7
after:7
before:8
after:8
before:9
after:9
before:10
CONTINUE
before:11
after:11
before:12
after:12
before:13
after:13
before:14
after:14
before:15
CONTINUE
=== STOP

But when we use CONTINUE in loop, that is based on implicit cursor, it gives wrong results:

SQL> begin
  2    dbms_output.put_line('=== START');
  3    for r in (select level num from dual connect by level <= 115) loop
  4      dbms_output.put_line('before:'||r.num);
  5      if mod(r.num, 5) = 0 then
  6        dbms_output.put_line('CONTINUE');
  7        continue;
  8      end if;
  9      dbms_output.put_line('after:'||r.num);
 10    end loop;
 11    dbms_output.put_line('=== STOP');
 12  end;
 13  /
=== START
before:1
after:1
before:2
after:2
before:3
after:3
before:4
after:4
before:5
CONTINUE
before:101
after:101
before:102
after:102
before:103
after:103
before:104
after:104
before:105
CONTINUE
=== STOP

In that case CONTINUE statement goes to iteration no 101 instead of going to iteration 6, as expected!!
To make the long story short, I've experiment with few setting and found that setting PLSQL_OPTIMIZE_LEVEL to 1 this block runs as expected:

SQL> ALTER SESSION SET PLSQL_OPTIMIZE_LEVEL = 1;
SQL> begin
  2    dbms_output.put_line('=== START');
  3     for r in (select level num from dual connect by level <= 115) loop
  4       dbms_output.put_line('before:'||r.num);
  5       if mod(r.num, 5) = 0 then
  6         dbms_output.put_line('CONTINUE');
  7         continue;
  8       end if;
  9       dbms_output.put_line('after:'||r.num);
 10     end loop;
 11     dbms_output.put_line('=== STOP');
 12  end;
 13  /
=== START
before:1
after:1
before:2
after:2
before:3
after:3
before:4
after:4
before:5
CONTINUE
before:6
after:6
[... many lines cutted out from output...]
after:99
before:100
CONTINUE
before:101
after:101
before:102
after:102
before:103
after:103
before:104
after:104
before:105
CONTINUE
before:106
[... many lines cutted out from output...]
after:114
before:115
CONTINUE
=== STOP

For me it looks as bug in PL/SQL Optimizer on level 2. In that case PL/SQL does bulk collect for 100 rows when FOR LOOP with cursor is used. Seems that CONTINUE in that case causes to fetch next portion of records instead of taking next record from buffer. I've reported bug to Oracle Support, but until it will get fixed, be aware of possible wrong results.
This was tested on Oracle 11.1.0.6 and 11.1.0.7 Enterprise Edition.

Keep reading,
Paweł

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Book Review: Processing XML documents with Oracle JDeveloper 11g

Written by Paweł Barut
This time I would like to recommend a book Processing XML documents with Oracle JDeveloper 11g published by PacktPub.com. As I have some experience with XML processing inside Oracle DB (XMLDB) I was lacking the knowledge of XML manipulation in Java, especially using Oracle JDeveloper. This book is rather not for beginners - you should have basic knowledge of what is XML, at least theoretically. From the book you can learn how to manage XML Schemas in JDeveloper, then write XML documents based on those schema and finally validate them in JDeveloper or write Java code to validate it automatically. Chapters that I value much are those describing how to generate PDF documents. There are two methods described - one using Apache FOP API , and Oracle XML Publisher. As I was not generating PDF's this way so far, I found those 2 chapters very interesting. There is also chapter on generatin Excel by transformation of XML using Apache HSSF API .

Book is very practical. If you want to start with subjects described above then this book is for you. Of course it does not mean that you do not have to study documentation. However, it will be easier for you to make first steps. Beside describing Oracle JDeveloper, author also shows how to install and use Oracle Berkley XML DB to store, query and update XML Documents - using command line and XML DB API.

I especially recommend eBook version. All URLs in eBook version are active, so linking to web pages are very simple. Also coping sample code is easy. This book contains many practical and usefull tips on XML processing and tools as well. So if those XML aspects are in your interest, then it's definitelly good to invest in this book.

Keep reading,
Paweł

--
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Multiplying texts and null effect

Written by Paweł Barut
This time short notice on side effect of implicit type conversion ans short expression evaluation. Let me show this on example - try this statement:

SQL> select 'a'*'b' from dual;
select 'a'*'b' from dual
       *
ERROR at line 1:
ORA-01722: invalid number

As expected we get error. It is due to fact that multiplexing operator (*) is expecting numbers on both sides, an implicit conversion takes place. However this statement:

SQL> select ''*'b' from dual;

    ''*'B'
----------

does not give error. How is it possible? In oracle empty string is in fact an null. null multiplied by any number gives null, so due to optimization oracle decided to evaluate this expression to null.
As you know also 0 (zero) multiplied by any number gives zero. So let's test it:

SQL> select '0'*'b' from dual;
select '0'*'b' from dual
           *
ERROR at line 1:
ORA-01722: invalid number

In that case Oracle did not optimized evaluation, and decided to make full calculation. I do not know the reason for different behaviour but is repeatable (at least on instances I've access to).
My recommendation: always make sure that you provide data in proper data-type. Make explicit data conversion using to_number, to_date or to_char functions.

Keep reading,
Paweł

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