Showing posts from August, 2009

Open Office Wiki Publisher

Java Pose

32 bit Windows and memory above 4 GB

Oracle composite indexes

ssh agent to eliminate remote login password prompt

Configure and run the ssh agent to eliminate the need to manually login to a remote system to execute commands.

Ubuntu default setup comes with ssh agent automatically - you just need to configure it.

1. Generate a private key: ssh-keygen -t dsa
2. Copy this key to the correct place on the remote machine, usually this is: ~/.ssh/authorized_keys
3. Run ssh-add This require you to enter your local passphrase and your remote password. You can also set up Ubuntu to ask you this passphrase at login

ps -u <username> | grep ssh-agent

What is it and how do I use it?

Oracle function based index

Richard Foote's Blog

Slides explaining implications and performance of function indexes and computed columns.

Optimization steps:

- Execute show plan before optimization - record and review
- Check row count of tables in where clause to see impact of full table scans
- Measure query performance to see if improvement is necessary
- Index and or rewrite queries as necessary
- Execute show plan to validate index selection by the CBO
- Measure the query performance to validate gains
- Document and share your results with the team

For Function-based indexes:

- Create a function that computes a virtual column
- Create a function based index on the virtual column computed by the function
- Use the virtual column via the function in the query where clause

Syntax for function-based indexes:

create [unique | nonclustered] index index_name
on [[ database.] owner.] table_name
(column_expression [asc | desc]
[, column_expression [asc | desc]]...

set showplan on
set noexec on

select * FROM someTable WHERE (fiel…

Installing Subversion

Followed this link to install svn

mkdir src
cd src
tar -xvjpf subversion-1.6.4.tar.bz2
tar -xvjpf subversion-deps-1.6.4.tar.bz2
cd subversion-1.6.4
./configure --prefix=$HOME --without-berkeley-db --with-ssl LDFLAGS="-L/lib64"
make install

installing subversion on bluehost

Setup repository and start server

creating repository linux from

ssh setup

svn book

The below didn't work:
Followed this link with corrections and modifications to install svn on hostmonster


SQL server

JBoss Log4j doesn't load dtd from classpath

Sybase JDBC driver source code

SwisSQL Database migration tools

Hibernate field level access queries db on getId

When a Hibernate entity is performing field level access, it initializes the proxies and queries the database even though the proxy has the id when getId method is called.

Hibernate cache

Caching and flushing

Monitor statistics in jboss jmx-console:
* name=statistics

Ehcache performance
Ehcache docs

Hibernate Caches

Hibernate cache documentation

Truly Understanding Hibernate Second-Level Cache

From above article:

The cache is holds strings, and serializable identifiers for relationships. The cache does *not* holding on to actual instances of the objects. Why is this important? Two reasons. One, Hibernate doesn't have to worry that client code (i.e. your code) will manipulate the objects in a way that will disrupt the cache, and two, the relationships and associations do not become 'stale', and are easy to keep up to date as they are simply identifiers.

The default setting is to not cache associations; and if you are not aware of this, and simply turn on caching quickly without really reading into how caching works in Hibernate, you will add the overhead of managing the cache without adding much of the benefits. After all, the primary benefit of cach…

Put Windows in its place

I am so happy! Ubuntu and VirtualBox have made it possible to, "Put Windows in its place". Windows is now safely sandboxed and subservient to a *nix operating system. I can now start, stop, reboot it, and constrain Windows use of resources without rebooting my entire system. VirtualBox seamless mode even allows me to run Windows applications as individual Windows right on my Ubuntu desktop. This is so much nicer than the WINE palarva.

I installed Windows once under VirtualBox and can now clone it on my system from a single file. If it gets messed up, I only have to copy the original Windows install file which is safely backed up; no need to ever reinstall Windows again. I can make separate instances of Windows if/when I need one for a particular Windows only application, i.e., Enterprise Architect, Quicken, etc.

The world of computing has become a better place.

Thank you!