Constraints

To keep integrity within typically an event source when appending events to an event sequence, you can leverage constraints. Constraints are rules that run on a database level within Chronicle, allowing or not allowing an event to be appended.

Unique Constraint

A unique constraint specifies events that work on a specific value you want to keep unique within an event source. For instance, lets say you're creating a system for registering users, the user name is typically something you want to keep a unique constraint on. Any events that either create the user or modify the user name in any way would typically then be included in the constraint definition.

Unique Event Type Constraint

The unique event type constraint lets you constrain on a specific event type being unique per event source. If any attempts of appending the same event type twice for an event source is done, it will not be a constraint violation.