Struct Migration 

pub struct Migration { /* private fields */ }

Abstract base class for user-defined migrations.

Purpose

Represents a versioned database schema migration that can be applied to upgrade the database from one schema version to another. Encapsulates migration steps and provides lazy execution semantics.

Characteristics

• Immutable public API with internal mutable state via Arc<Mutex<>>
• Clone-able: clones share the same underlying migration state via Arc
• Lazy execution: migration steps are generated on first call to steps()
• Idempotent: multiple steps() calls return cached results (execute() called once)
• Closure-based: migration logic defined by user-provided function

Usage

let migration = Migration::new(1, 2, |instruction| {
    instruction.for_database().add_user("admin", "password")
        .drop_collection("test");
    instruction.for_collection("users").rename("customers");
    instruction.for_repository("books", None).delete_field("price");
    Ok(())
});

// Apply to database
let db = Nitrite::builder()
    .schema_version(2)
    .add_migration(migration)
    .open_or_create(Some("admin"), Some("password"))?;

Implementations

impl Migration

pub fn new( from_version: u32, to_version: u32, migrate: impl Fn(&InstructionSet) -> NitriteResult<()> + Send + Sync + 'static, ) -> Self

Creates a new migration for upgrading from one schema version to another.

Arguments

• from_version - Source schema version
• to_version - Target schema version
• migrate - Closure that defines migration operations via InstructionSet

Returns

Migration instance wrapping the migration logic

Behavior

• The migrate closure is not executed immediately
• Execution is deferred until first call to steps() or execute()
• Closure receives immutable InstructionSet reference for building instructions

pub fn from_version(&self) -> u32

Returns the source schema version for this migration.

Returns

Schema version as u32

pub fn to_version(&self) -> u32

Returns the target schema version for this migration.

Returns

Schema version as u32

pub fn steps(&self) -> NitriteResult<Vec<MigrationStep>>

Returns all migration steps, triggering lazy execution on first call.

Returns

Ok(Vec<MigrationStep>) - All migration steps generated by the migration closure Err(NitriteError) - If migration execution fails or state access fails

Behavior

• First call executes the migration closure to generate steps
• Subsequent calls return cached steps without re-execution
• Executed flag prevents duplicate execution

Trait Implementations

impl Clone for Migration

fn clone(&self) -> Migration

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Migration

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.