Databases on iniy.org

Importing tpc-h testdata into mongodb

Fri, 28 Jun 2013 14:52:45 +0000

As written in a former post, tpc-h offers an easy possiblity to generate various amounts of testdata. Download dbgen from this website and compile it: http://www.tpc.org/tpch/

now run

./dbgen -v -s 0.1

this should leave you with some *.tbl files (PIPE separated csvfiles). Now you can use my scripts to convert them into json an import them into mongodb.
i packed already some generated files into the archive and added the header, so you don’t have to generate the tbl-files by yourself. You only have to adjust the load_into_mongodb.sh script so it loads into the correct database (if test is not ok for you).

Importing large csv-files into mongodb

Fri, 21 Jun 2013 10:47:04 +0000

I wanted to import some dummy data into Mongo-DB to test the aggregation functions. I thought a nice source would be the tpc-h testdata which can generate arbitrary volumes of data from 1 GB to 100 GB. You can download the data generation kit from the website : http://www.tpc.org/tpch/

Oracle exp export with full tns-string

Thu, 24 May 2012 08:55:07 +0000

Handling the oracle tns-names file can be a pain in the ass, especially if you don’t want to rely on it. For example you want a user to enter dynamically a connection with typical “host, port, sid, username, password” configuration. In oracle you can also use the full tns-string to connect to a database. I struggled some time finding the correct escape and quotation configuration, but finally this worked:

oracle day 2: datafile is missing

Tue, 22 Jun 2010 21:30:23 +0000

playing around with oracle the other day I added a new tablespace and thought it would be smart to put the corresponding datafile on my tmp-directory. At first everything worked fine, now some days later I wanted to check out the java jdbc connector for oracle, but the database didn’t start up. So first lesson I learned, thats where oracle errorlog-files are located:

oracle day 1: first steps with oracle

Tue, 22 Jun 2010 21:27:48 +0000

recently I am familiarizing myself with the Oracle Database and I want to share my first impressions with you.

A good start seemed to me the free oracle-xe version. I started the install with this tutorial and everything worked quite straight-forward.

Find slow-queries in MySQL

Wed, 14 Oct 2009 21:26:31 +0000

Often when a web-application seems slow it’s not (or not only) the parse time, but also or mayorly database speed. Most scripting-languages don’t act “intelligent” in parsing as it would be best for user experience, but go through the code line by line (whom would expect it otherwise?). So if you have a website containing some slow MySQL-Queries it seems as if all the page just takes a eternity to load. One step would be to put all the page loading into some seperate code-piece and load it later with ajax-technology. This gives a great boost in user-experienced speed, because the most parts of the website load and are already usable before the database content pops in. But otherwise often not the database is the problem, but bad written querys. But how to find them? Luckily mysql already provides us with a feature called slow-query-log which can be activated easily through my.cnf. So just look for this: