Vertical Sharding of Database

Often we have slow-moving data in the distributed databases which need to be separated from the other data. Similarly, there might be some sensitive data like passwords that need extra security controls. Vertical sharding of databases plays a crucial role in all these cases by separating desired data from the rest of the data or enabling extra security controls over some data.

Vertical sharding

We can put different tables in different database instances (that might be running on a different physical server). We might break a table into multiple tables such that some columns are in one table, while the rest are in the other. Often care should be taken if there are joins between multiple tables. We might like to keep such tables together on one shard.

Often vertical sharding is used to increase the speed of data retrieval from a table consisting of columns containing very wide text or Binary Large Object (BLOB). In this case, the column having large text or BLOB is split into a different table. As shown in the following figure Employee table is divided into two tables: a reduced Employee table and EmployeePicture table. The EmployePicture table has just two columns EmployeID and Picture, separated from the original table. Moreover, the primary key EmpoloyeeID of the Employee table is added in both partitioned tables. This makes the data read and write easier and the reconstruction of the table is performed efficiently.