Expressions in Aerospike
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This tutorial describes how expressions work in Aerospike: how they are formed, their syntax, benefits, and how they are used in filters and operations.
This tutorial requires an Aerospike database running locally. See Setup to get started.
Introduction
In this tutorial, we will see how expressions work in Aerospike and benefits they provide.
The expressions functionality has been enhanced in Aerospike Database 5.6. Expressions appear in two flavors in the client library: Filter Expressions and Operation Expressions. Filter Expressions provide a mechanism to select records for operations. Operation Expressions enable new read and write capabilities as described later. Expressions are also used on server as XDR Filter Expressions to specify which records are shipped to remote destinations.
We will describe at a high level how expressions are formed in Aerospike and the capabilities they enable. After highlighting key syntax patterns, we will show with specific code examples how expressions are used.
The main topics in this tutorial include:
- scope of expressions
- benefits
- syntax
- usage
- coding examples
Prerequisites
This tutorial assumes familiarity with the following topics:
In this tutorial
Setup
Verify your database is running, install the client, and initialize the connection.
Understanding expressions
Learn what expressions are, how Aerospike uses them, and the benefits they provide.
Syntax and coding patterns
Learn Polish notation, variables, conditional evaluation, and how expressions are built.
Filter expressions
Select records for queries and scans, with a full runnable example.
Operation expressions
Read and write computed values server-side, avoiding read-modify-write round trips.
Operation expressions example
A full runnable example: compute grades and generate a report server-side.
Usage notes and next steps
Caveats, takeaways, and further resources.