Comments for Crazy Idea

Comment on How to view certificate(s) details of a LDAP server? by Michael Tim

Michael Tim — Sat, 28 Feb 2009 18:05:36 +0000

I love your site!

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Comment on Is anybody in production using Java 6 by Michael Tim

Michael Tim — Sat, 28 Feb 2009 17:32:02 +0000

I love your site!

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Comment on tags by Michael Tim

Michael Tim — Sat, 28 Feb 2009 17:16:45 +0000

I love your site!

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Comment on Jdbc : Why doesn’t Oracle’s driver support READ_UNCOMMITTED ? by anjan bacchu

anjan bacchu — Thu, 16 Oct 2008 08:47:09 +0000

answering the tool part of the question myself.

datastorm is a tool : http://datastorm.sourceforge.net/motivation.html
that will launch a SWT app with the same connection used for the unit test.

this tool lets the unit tester to go into the GUI and then run queries for all you want. That will make unit testing a lot more easier for those difficult cases.

It might NOT even be a bad idea to have the setup() method launch the datastorm tool by default — just in case it is needed. Anyhow, most of the time, connection is obtained once per test case.

Comment on Jdbc : Why doesn’t Oracle’s driver support READ_UNCOMMITTED ? by Slava Imeshev

Slava Imeshev — Sun, 10 Aug 2008 08:19:54 +0000

My understanding is that Oracle just cannot do the READ_UNCOMMITTED because it uses versioned snapshots. Once you started reading, you read the same data from the snapshot which is detached from the “current” state of the table. This approach to concurrency makes READ_UNCOMMITTED simply impossible.

Comment on Is anybody in production using Java 6 by anjanb

anjanb — Thu, 20 Mar 2008 20:56:49 +0000

I heard that yahoo’s search team is in production using java 6 along with Hadoop, etc.

How about other guys doing enterprise stuff ?

Comment on Jdbc : Why doesn’t Oracle’s driver support READ_UNCOMMITTED ? by Dr. Java

Dr. Java — Wed, 03 Oct 2007 11:33:49 +0000

For your convenience, Tom's answer can be found on his site.

Comment on Jdbc : Why doesn’t Oracle’s driver support READ_UNCOMMITTED ? by peter veentjer

peter veentjer — Sat, 08 Sep 2007 15:19:34 +0000

Databases that use Multiversion concurrency control (oracle, postgresql, mysql&innodb, firebird etc) don’t need dirty reads. A dirty read is useful if you want to do a non blocking read, but Multiversion Concurrency Control (MVCC) database have a different solution. Instead of reading uncommitted data, a previous committed version of a record is used (hence the name multiversion). This approach is much saver because you can’t read uncommitted data (so data that never made it into the db) or data that is not valid (data could be written before its constraints are checked).

That is why a READ_UNCOMMITTED isolation level is ugraded to READ_COMMITTED.

A similar explanation can be used for REPEATABLE_READS. The SERIALIZED isolation level also prevents unrepeatable reads from happening and the serialized isolation level is quite easily realized in oracle (also based on the multiversion mechanism and optimistic locking at the end of serialized transaction commit). That is why REPEATABLE_READ is automatically upgraded to SERIALIZED.

Comment on Jdbc : Why doesn’t Oracle’s driver support READ_UNCOMMITTED ? by anjanb

anjanb — Sat, 08 Sep 2007 00:48:01 +0000

Hi Morgan,

Thank you.

Guess it’s time to refresh my Oracle fundas by reading the WROX PRESS “EXPERT ONE-ON-ONE ORACLE”. I’m sure Tom would give me a hint as to why they do it.

Do, do other DBs(like MS-SQL, MySQL, DB2) allow Dirty Reads ? How about Java DB, HSQL, etc ?

Thanks again,

BR,
~A

Comment on Jdbc : Why doesn’t Oracle’s driver support READ_UNCOMMITTED ? by Morgan

Morgan — Fri, 07 Sep 2007 21:34:18 +0000

Because transaction isolation levels READ_UNCOMMITTED and REPEATABLE_READ don’t exist in Oracle databases by design.