Emerging DB Technology – Columnar Database

Posted by Venkata Emani
August 24th, 2012


Today’s Top Data-Management Challenge:

Businesses today are challenged by the ongoing explosion of data. Gartner is predicting data growth will exceed 650% over the next five years. Organizations capture, track, analyze and store everything from mass quantities of transactional, online and mobile data, to growing amounts of machine-generated data. In fact, machine-generated data, including sources ranging from web, telecom network and call-detail records, to data from online gaming, social networks, sensors, computer logs, satellites, financial transaction feeds and more, represents the fastest-growing category of Big Data. High volume web sites can generate billions of data entries every month.

As volumes expand into the tens of terabytes and even the petabyte range, IT departments are being pushed by end users to provide enhanced analytics and reporting against these ever increasing volumes of data. Managers need to be able to quickly understand this information, but, all too often, extracting useful intelligence can be like finding the proverbial ‘needle in the haystack.

How do columnar databases work? The defining concept of a column-store is that the values of a table are stored contiguously by column. Thus the classic supplier table from supplier and parts database would be stored on disk or in memory something like:  S1S2S3S4S52010302030LondonParis Paris LondonAthensSmithJonesBlakeClarkAdams

This is in contrast to a traditional row-store which would store the data more like this:

S120LondonSmithS210Paris JonesS330Paris BlakeS420LondonClarkS530AthensAdams

From this simple concept flows all of the fundamental differences in performance, for better or worse, between a column-store and a row-store. For example, a column-store will excel at doing aggregations like totals and averages, but inserting a single row can be expensive, while the inverse holds true for row-stores. This should be apparent from the above diagram.

The Ubiquity of Thinking in Rows:

Organizing data in rows has been the standard approach for so long that it can seem like the only way to do it. An address list, a customer roster, and inventory information—you can just envision the neat row of fields and data going from left to right on your screen.

Databases such as Oracle, MS SQL Server, DB2 and MySQL are the best known row-based databases.

Row-based databases are ubiquitous because so many of our most important business systems are transactional.

Data Set Ex:  See the below data set contents of 20 columns X 50 Millions of Rows.

Example Data Set

Row-oriented databases are well suited for transactional environments, such as a call center where a customer’s entire record is required when their profile is retrieved and/or when fields are frequently updated. Other examples include:

• Mail merging and customized emails

• Inventory transactions

• Billing and invoicing

Where row-based databases run into trouble is when they are used to handle analytic loads against large volumes of data, especially when user queries are dynamic and ad hoc.

To see why, let’s look at a database of sales transactions with 50-days of data and 1 million rows per day. Each row has 30 columns of data. So, this database has 30 columns and 50 million rows. Say you want to see how many toasters were sold for the third week of this period. A row-based database would return 7-million rows (1 million for each day of the third week) with 30 columns for each row—or 210-million data elements. That’s a lot of data elements to crunch to find out how many toasters were sold that week. As the data set increases in size, disk I/O becomes a substantial limiting factor since a row-oriented design forces the database to retrieve all column data for any query.

As we mentioned above, many companies try to solve this I/O problem by creating indices to optimize queries. This may work for routine reports (i.e. you always want to know how many toasters you sold for the third week of a reporting period) but there is a point of diminishing returns as load speed degrades since indices need to be recreated as data is added. In addition, users are severely limited in their ability to quickly do ad-hoc queries (i.e. how many toasters did we sell through our first Groupon offer? Should we do it again?) that can’t depend on indices to optimize results.


Pivoting Your Perspective: Columnar Technology

Column-oriented databases allow data to be stored column-by-column rather than row-by-row. This simple pivot in perspective—looking down rather than looking across—has profound implications for analytic speed. Column-oriented databases are better suited for analytics where, unlike transactions, only portions of each record are required. By grouping the data together this way, the database only needs to retrieve columns that are relevant to the query, greatly reducing the overall I/O.

Returning to the example in the section above, we see that a columnar database would not only eliminate

43 days of data, it would also eliminate 28 columns of data. Returning only the columns for toasters and units sold, the columnar database would return only 14 million data elements or 93% less data. By returning so much less data, columnar databases are much faster than row-based databases when analyzing large data sets. In addition, some columnar databases (such as Infobright®) compress data at high rates because each column stores a single data type (as opposed to rows that typically contain several data types), and allow compression to be optimized for each particular data type. Row-based databases have multiple data types and limitless range of values, thus making compression less efficient overall.

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