Wide column stores, or column-oriented database systems, are storage systems that store data by columns rather than by rows. For example, consider the following simple table:
|
FirstName |
LastName |
Age |
|
John |
Smith |
42 |
|
Bill |
Cox |
23 |
|
Jeff |
Dean |
35 |
In an RBDMS, the tuples would be stored row-wise, so the data on the disk would be stored as follows:
John,Smith,42|Bill,Cox,23|Jeff,Dean,35
In online-transaction-processing (OLTP) applications, the I/O pattern is mostly reading and writing all of the values for entire records. As a result, row-wise storage is optimal for OLTP databases.
In a columnar database however, all of the columns are stored together. So, the tuples would be stored as follows:
John,Bill,Jeff|Smith,Cox,Dean|42,23,35
The advantage here is that if we want to read values such as FirstName, reading one disk block reads...
