Database Reference
In-Depth Information
Chapter 5. Query and Scan Operations in
DynamoDB
In the previous chapter, we learned to create a secondary index for a table and its role in re-
trieving the items efficiently. In the long run, knowledge of the secondary index is useful
only if we know how to use it for retrieval. Item retrieval can be done in DynamoDB using
two operations called query and scan. Similarly we also discussed sharding. In this chapter,
we will learn about parallel scanning, which makes use of the sharding concept. The
primary objective of any database (whether it be NoSQL or SQL) is to provide easy storage
and faster retrieval of data. So far, we have discussed various configurations that can be ad-
ded to our table, such as adding an index, specifying the primary key, and so on. In this
chapter, we will cover the following topics:
• Querying table items
• Scanning table items
• Parallel scanning
First, we will discuss the query operation, which makes use of the hash and range key val-
ues to retrieve the items. Then we will shift our focus to the scan operation, which will scan
the entire table. Finally we will discuss the limitations of (sequential) scan operations,
which give rise to parallel scanning.
