Sunday, November 16, 2014

Java Performance Analyser

Occasionally I get "Out Of Memory" error in my Apache Tomcat and with out thinking too much I will just bounce the server to solve the problem. I was searching for the same in Google and it took me to a blog post in which I found an interesting tool Visual VM.
My goal is not to re-produce every detail about this tool, Name says it all.
I just downloaded it and got up and running in seconds. I have not yet started playing with the tool, but I believe this will solve some of my Java Memory issues.
You can go through the screen cast of this tool from this page.

Saturday, November 15, 2014

Connecting to Oracle from KDB+ (Using Babel)

I have recently started messing around KDB+ and playing with cryptic Q language.

I want to compare the performance of Oracle vs KDB+, and in order to do that I have to duplicate the Oracle table in KDB+. I tried through ODBC layer but didn't work. Then I found another elegant solution posted on the site using Babel.
"Babel for kdb+ is a SQL gateway process that allows kdb+ to query other vendors databases via jdbc."
Babel act as a broker between KDB+ and any database that can be connected through JDBC library. Meaning KDB knows how to talk to Babel and Babel knows how to talk to Databases through JDBC Layer. Now lets get into details.

Step 1:
Download Babel:  wget
and unzip it.

Step 2:
Download ojdbc7.jar from oracle and copy it to bin directory under Babel. Note: odbc7 is for JDK 1.7 and if your Java version (java -version) is 1.6 you should use odbc6.jar.
Update: If you are using Java 8/JDK1.8 you can download ojdbc8 from here
Update: For SQL Server use this thread

Step 3: Start the babel on port 6868

$ java -Xmx1024m -Doracle.jdbc.defaultRowPrefetch=10000 -cp "babel.jar:lib/ojdbc7.jar" de.skelton.babel.Babel 6868 oracle.jdbc.OracleDriver

For SQL Server
java -Xmx1024m -cp "babel.jar:sqljdbc42.jar" de.skelton.babel.Babel 6868

Step 4:
Start q (I assume you already have working instance of q). If not you should first learn about q from

q)h:hopen 6868
q)r:h("query";"jdbc:oracle:thin:scott/tiger@your_oracle_server:1521:orcl";"select * from emp");

PS: You know Scott/Tiger is user id/ password and ORCL is the Oracle instance.

More References: