Module migration 

Schema migration support for database evolution.

This module provides mechanisms to manage database schema changes over time. As applications evolve, their data structures change, and migrations enable safe transformation of existing data.

Migration Process

A migration:

1. Defines source and target schema versions
2. Specifies transformation steps for affected data
3. Is executed automatically when opening a database with a different schema version

Creating Migrations

use nitrite::migration::{Migration, MigrationStep};

let migration = Migration::create(1, 2)
    .add_instruction(/* ... */)
    .finalize();

let db = Nitrite::builder()
    .schema_version(2)
    .add_migration(migration)
    .open_or_create(None, None)?;

Migration Types

• Collection Instructions: Add/remove collections, create indexes
• Repository Instructions: Define object repository structure
• Database Instructions: Global database-level changes

Atomicity

Migrations are applied atomically - either all changes succeed or none are applied. If a migration fails, the database is rolled back to its previous state.

Structs

CollectionInstructionBuilder

Builder for collection-level instructions.

DatabaseInstructionBuilder

Builder for database-level instructions.

InstructionSet

Default implementation of InstructionSet

Migration

Abstract base class for user-defined migrations.

MigrationManager

Manages database migrations including version tracking and execution

MigrationStep

Represents a single migration step with its type and arguments.

RepositoryInstructionBuilder

Builder for repository-level instructions.

Enums

InstructionType

All instruction types supported by the migration system.

MigrationArguments

Type-erased arguments container for migration operations.

MigrationFn

Unified wrapper enum for all migration function closures that can be type-erased and downcasted.

Traits

CollectionInstruction

Collection-level migration instructions.

DatabaseInstruction

Database-level migration instructions.

Instruction

Base trait for all migration instructions.

RepositoryInstruction

Repository-level migration instructions.