Struct Step 

pub struct Step { /* private fields */ }

A Migration built from closures — what the builder methods produce.

Implement Migration directly when a migration wants a name of its own and a place to live; use Step when it is two lists of statements.

Implementations

impl Step

pub fn new( name: impl Into<String>, up: impl Fn(Dialect) -> Vec<String> + Send + Sync + 'static, down: impl Fn(Dialect) -> Down + Send + Sync + 'static, ) -> Self

A step from an up and a down renderer.

pub fn raw(name: impl Into<String>, up: Vec<String>, down: Vec<String>) -> Self

A step running fixed SQL either way, whatever the dialect.

pub fn raw_irreversible( name: impl Into<String>, up: Vec<String>, reason: impl Into<String>, ) -> Self

A step that applies fixed SQL and cannot be undone, with the reason.

pub fn create_table<E: Entity>(name: impl Into<String>) -> Self

A step creating E’s table and its indexes, from the derived metadata.

Its down drops the table, which is the honest inverse — and also why rolling back a create_table in production destroys data. That is a property of the operation, not of this implementation.

pub fn create( name: impl Into<String>, table: impl Into<String>, build: impl FnOnce(&mut Blueprint), ) -> Self

A step creating table from a Blueprint — Laravel’s Schema::create.

For a table no model describes: a pivot, a join table, something a third-party tool reads. The description is written once and lowered to whichever engine the executor reports, so there is no per-dialect SQL to keep in step.

Step::create("0007_create_post_tag", "post_tag", |table| {
    table.foreign_id("post_id").constrained_on("posts").cascade_on_delete();
    table.foreign_id("tag_id").constrained_on("tags").cascade_on_delete();
    table.primary(["post_id", "tag_id"]);
})

Its down drops the table — which is the honest inverse, and also why rolling one back in production destroys data.

pub fn table( name: impl Into<String>, table: impl Into<String>, build: impl FnOnce(&mut TableChanges), ) -> Self

A step changing a table that already exists — Laravel’s Schema::table.

Step::table("0008_posts_add_subtitle", "posts", |table| {
    table.string("subtitle").nullable();
    table.index(["author_id", "published"]);
})

The down is derived from what changed, so it cannot drift from the up the way a hand-written one does. Where a change genuinely cannot be undone — a dropped column, a raw statement with no reverse — the step reports itself irreversible and says which change made it so.

pub fn drop_table(name: impl Into<String>, table: impl Into<String>) -> Self

A step dropping a table.

Irreversible, and deliberately so: nothing here knows the shape of what it dropped, and a down that recreated an empty table would report success having restored nothing.

pub fn rename_table( name: impl Into<String>, from: impl Into<String>, to: impl Into<String>, ) -> Self

A step renaming a table. Reverses by renaming it back.

ALTER TABLE … RENAME TO on SQLite and Postgres, RENAME TABLE on MySQL — one of the several places the engines simply disagree.

Trait Implementations

impl Debug for Step

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

Formats the value using the given formatter.

impl Migration for Step

fn name(&self) -> &str

The name recorded in the ledger.

fn up(&self, dialect: Dialect) -> Vec<String>

The statements that apply this migration to dialect.

fn down(&self, dialect: Dialect) -> Down

How to undo it.