View Concepts

This section covers the key concepts that underpin Akka Views, explaining how they work and how to use them effectively in your applications.

Core Concepts

Data Structure and Access

Table Updaters - The fundamental building blocks of Views, defining data sources and table structures
Data Types - The supported data types in Views and how they map between Java and the query language
Result Mapping - How query results are transformed into Java objects in your application

Specialized Data Handling

Optional Fields - Working with values that may or may not be present
Array Types - Handling collections of values within a single view row

Advanced Features

Advanced Views - Creating sophisticated views with multiple tables, joins, and complex data structures

Understanding Views

Views in Akka provide a flexible way to access your data using patterns beyond simple key-based lookups. They create queryable projections of your entities that can be optimized for specific access patterns.

How Views Work

Data Consumption: Views subscribe to events or state changes from entities or topics
Transformation: These events/changes are transformed into rows in view tables
Indexing: Views automatically create indexes based on your queries
Querying: The view query language allows you to retrieve and filter this data

View Benefits

Flexible Access Patterns: Access data by any field, not just entity IDs
Optimized Queries: Views create indexes for efficient querying based on your needs
Joined Data: Combine data from multiple entities into unified query results
Custom Projections: Transform entity data into formats optimized for reading

View Characteristics

Eventually Consistent: Views are eventually consistent with their source entities
Read Optimized: Views are designed for efficient reading, not for updates
Declarative Definition: Views are defined by their queries and transformations
Automatic Maintenance: Updates to views happen automatically as entities change

From Entity to View

Understanding the relationship between entities and views is key to effective modeling:

Entity Focus vs. View Focus

Entities: Focus on business logic, command handling, and state consistency
Views: Focus on data access patterns, querying, and read optimizations

Data Flow

Clients send commands to entities
Entities process commands and emit events or state changes
Views consume these events/changes and update their tables
Clients query views to read data in the desired format

Creating Effective Views

Define views based on access patterns in your application
Consider different views for different query needs
Design your table structure and queries together
Balance normalization and denormalization based on query patterns