NoSQL Tutorial

Some months ago I had a discussion with NoSQL creator, Carlo Strozzi, regarding the databases.

I should admit, I am an SQL fan! It's hot having the same language, no matter which platform or database engine is used. He underlined the fact that most SQL engines lack of flexibility and waste system resources (memory and disk space) because of their multi-platform environment (such as Oracle, DB2, Informix, etc.).

He suggested I have a look at the white paper that inspired him: “The UNIX Shell As a Fourth Generation Language” by Evan Schaffer (evan@rsw.com) and Mike Wolf (wolf@hyperion.com).

Quoting from the above paper:

The UNIX file structure is the fastest and most readily-available database engine ever built: directories may be viewed as catalogs and tables as plain ASCII files. Commands are common UNIX utilities, such as grep, sed and awk. Nothing should be reinvented.

NoSQL was born with these ideas in mind: getting the most from the UNIX system, using some commands that glue together various standard tools. Although NoSQL is a good database system, this is not a panacea for all you problems. If you have to deal with a 10 gigabytes table that must be updated each second from various clients, NoSQL doesn't work for you since it lacks of performance on very big tables, and on frequent updates you must be in real time. For this case, I suggest you use a stronger solution based on Oracle, DB2 or such packages on a Linux cluster, AS/400 or mainframes.

However, if you have a web site containing much information and more reading occurs than writing, you will be surprised how fast is it. NoSQL (pronounced noseequel, as the author suggests) derives most of its code from the RDB database developed at RAND Organization, but more commands have been built in order to accomplish more tasks.

The latest NoSQL source code can be found at ftp://ftp.linux.it/pub/database/NoSQL, but RPM and Debian packages are also available. At the time of writing, latest stable version is 2.1.3.

Just unpack the source using the command tar -xzvvf nosql-2.1.3.tar.gz in a convenient directory (such as $HOME/src), and you will get all the code in the nosql-2.1.3 subdirectory. Enter the above subdirectory and do the following:

./configure
make
make install

The software will put its engine into /usr/local/lib/nosql, its documentation in /usr/local/doc/nosql and a symlink /usr/local/bin/nosql that points to the real executable (/usr/local/lib/nosql/sh/nosql). You can change the directory prefix (e.g., /usr instead of /usr/local) invoking ./configure --prefix=/usr.

You should copy the sample configuration file to the $NSQLIB directory (i.e., /usr/local/lib/nosql). This is not required but it's useful for changing some parameters via configuration file instead of variables. The commands

cp nosql.conf.sample /usr/local/lib/nosql/nosql.conf
chmod 0664 /usr/local/lib/nosql/nosql.conf

will copy it with the right permissions. You can optionally have a personal NoSQL configuration file creating an $HOME/.nosql.conf with 0664 permission applied.

Although NoSQL installation is quite simple, I suggest you to read the INSTALL file: the author gives some good tips.

Now that the package has been installed, let's start getting acquainted with NoSQL commands through an example.

We are the usual Acme Tools Inc. which supplies stuffs to the Toonies land. We would like to track our customers, so we should create a first table in which we will list some customers details (such as code, phone, fax, e-mail, etc...). The best way to create tables from scratch is via template files.

A template file contains the column names of the table and associated optional comments separated by tabs and/or spaces. Comments may be also specified with the usual hash sign (#) as the first character of the line. The file below, customer.tpl, is our template for the customer table.

# Acme Tools, Inc.
# Customers table
#######################
CODE    Code number
NAME    Name/Surname
PHONE   Phone no
EMAIL   E-mail

Most of the NoSQL commands read from STDIN and write to STDOUT. The maketable command, which builds tables from templates, is one of these. Issuing the command

nosql maketable < customer.tpl

CODE    NAME    PHONE   EMAIL
----    ----    -----   -----

nosql maketable < customer.tpl > customer.rdb

The resulting command would be

nosql maketable < customer.tpl |
  nosql write -s customer.rdb.

The -s switch in the write operator suppress STDOUT, e.g., nosql write, similar to the tee UNIX utility, writes both to file and STDOUT, unless -s is specified.

Pay attention, because the write command does not do any locking on the output table: nosql lock table and nosql unlock table must be used for this purpose.