sea-orm-2

name	sea-orm-2
description	Expert guidance for SeaORM 2.0, Rust's async ORM with strongly-typed columns, nested ActiveModels, Entity Loader API, and entity-first workflow. Use when working with SeaORM entities, queries, migrations, relations, or any database operations in Rust projects using SeaORM. Covers the new 2.0 API patterns, anti-patterns to avoid, and migration from 1.0. Use when this capability is needed.
metadata	{"author":"FlyinPancake"}

SeaORM 2.0

This skill provides expert guidance for using SeaORM 2.0 properly, focusing on the new patterns and avoiding common pitfalls that stem from SeaORM 1.0 knowledge.

Quick Reference

• Walk-through of SeaORM 2.0
• Migration Guide (1.0 to 2.0)
• New Entity Format
• Strongly-Typed Column
• Nested ActiveModel

Entity Definition (2.0 Format)

SeaORM 2.0 uses #[sea_orm::model] with relations defined directly on the Model struct. This replaces the 1.0 pattern of separate Relation enums and Related trait impls.

Basic Entity

mod user {
    use sea_orm::entity::prelude::*;

    #[sea_orm::model]
    #[derive(Clone, Debug, PartialEq, Eq, DeriveEntityModel)]
    #[sea_orm(table_name = "user")]
    pub struct Model {
        #[sea_orm(primary_key)]
        pub id: i32,
        pub name: String,
        #[sea_orm(unique)]
        pub email: String,
    }

    impl ActiveModelBehavior for ActiveModel {}
}

Entity with Relations

mod user {
    use sea_orm::entity::prelude::*;

    #[sea_orm::model]
    #[derive(Clone, Debug, PartialEq, Eq, DeriveEntityModel)]
    #[sea_orm(table_name = "user")]
    pub struct Model {
        #[sea_orm(primary_key)]
        pub id: i32,
        pub name: String,
        #[sea_orm(unique)]
        pub email: String,
        #[sea_orm(has_one)]
        pub profile: HasOne<super::profile::Entity>,
        #[sea_orm(has_many)]
        pub posts: HasMany<super::post::Entity>,
    }
}

Relation Types

// Has-One
#[sea_orm(has_one)]
pub profile: HasOne<super::profile::Entity>,

// Has-Many
#[sea_orm(has_many)]
pub posts: HasMany<super::post::Entity>,

// Belongs-To (explicit foreign key mapping)
#[sea_orm(belongs_to, from = "user_id", to = "id")]
pub user: HasOne<super::user::Entity>,

// Many-to-Many via junction table
#[sea_orm(has_many, via = "post_tag")]
pub tags: HasMany<super::tag::Entity>,

// Self-referential
#[sea_orm(self_ref, via = "user_follower", from = "User", to = "Follower")]
pub followers: HasMany<Entity>,

Junction Table (Composite Primary Key)

#[sea_orm::model]
#[derive(Clone, Debug, PartialEq, DeriveEntityModel, Eq)]
#[sea_orm(table_name = "post_tag")]
pub struct Model {
    #[sea_orm(primary_key, auto_increment = false)]
    pub post_id: i32,
    #[sea_orm(primary_key, auto_increment = false)]
    pub tag_id: i32,
    #[sea_orm(belongs_to, from = "post_id", to = "id")]
    pub post: Option<super::post::Entity>,
    #[sea_orm(belongs_to, from = "tag_id", to = "id")]
    pub tag: Option<super::tag::Entity>,
}

For detailed entity patterns, see references/entity-patterns.md.

Strongly-Typed Columns (2.0)

Use COLUMN constant with typed fields instead of the untyped Column enum:

// 2.0 (preferred) -- compile-time type safety
user::Entity::find().filter(user::COLUMN.name.contains("Bob"))

// 1.0 (outdated) -- still works but prefer COLUMN
user::Entity::find().filter(user::Column::Name.contains("Bob"))

The COLUMN constant provides:

• Compile-time type checking
• Better IDE autocomplete
• Refactoring safety

ActiveModel Builder Pattern (2.0)

Creating with Nested Relations

// Create with nested relations
let bob = user::ActiveModel::builder()
    .set_name("Bob")
    .set_email("[e-mail]")
    .set_profile(profile::ActiveModel::builder().set_picture("Tennis"))
    .insert(db)
    .await?;

Adding Has-Many Children

let mut bob = bob.into_active_model();
bob.posts.push(
    post::ActiveModel::builder().set_title("My first post")
);
bob.save(db).await?;

Many-to-Many Relations

let post = post::ActiveModel::builder()
    .set_title("A sunny day")
    .set_user_id(bob.id)
    .add_tag(existing_tag)
    .add_tag(tag::ActiveModel::builder().set_tag("outdoor"))
    .save(db)
    .await?;

For complete ActiveModel patterns, see references/activemodel-patterns.md.

Entity Loader API (2.0)

The Entity Loader eliminates N+1 queries by intelligently using JOIN for 1-1 relations and data loader for 1-N relations.

Basic Loading

// Load with relations in a single query
let bob = user::Entity::load()
    .filter_by_email("[e-mail]")
    .with(profile::Entity)
    .with(post::Entity)
    .one(db)
    .await?
    .expect("Not found");

Nested Relations

// Nested relations (post -> comments)
let user = user::Entity::load()
    .filter_by_id(12)
    .with(profile::Entity)
    .with((post::Entity, comment::Entity))
    .one(db)
    .await?;

How It Works

// join paths:
// user -> profile
// user -> post
//         post -> post_tag -> tag
let smart_user = user::Entity::load()
    .filter_by_id(42)
    .with(profile::Entity) // 1-1 uses join
    .with((post::Entity, tag::Entity)) // 1-N uses data loader
    .one(db)
    .await?
    .unwrap();

// 3 queries are executed under the hood:
// 1. SELECT FROM user JOIN profile WHERE id = $
// 2. SELECT FROM post WHERE user_id IN (..)
// 3. SELECT FROM tag JOIN post_tag WHERE post_id IN (..)

For advanced querying patterns, see references/query-patterns.md.

Schema Registry (Entity-First Workflow)

SeaORM 2.0 supports entity-first development where you define entities and SeaORM creates the schema.

// Auto-create tables from entity definitions (dev/testing)
db.get_schema_registry("my_crate::*")
    .sync(db)
    .await?;

This:

• Creates tables in topological order based on foreign key dependencies
• Adds new columns to existing tables
• Creates unique keys and foreign keys automatically

Requires feature flags: entity-registry and schema-sync.

Anti-Patterns to Avoid

1. Do Not Specify column_type on Custom Wrapper Types

// WRONG -- do not annotate column_type on custom types
#[sea_orm(column_type = "Decimal(Some((10, 4)))")]
pub speed: Speed,

// CORRECT -- SeaORM infers the column type from DeriveValueType
pub speed: Speed,

#[derive(Clone, Debug, PartialEq, DeriveValueType)]
pub struct Speed(Decimal);

2. Use Text for Long Strings on MySQL/MSSQL

// WRONG on MySQL/MSSQL -- silently truncates at 255 chars
pub description: String,

// CORRECT -- use column_type for longer strings
#[sea_orm(column_type = "Text")]
pub description: String,

// Also correct -- explicit max length
#[sea_orm(column_type = "String(StringLen::Max)")]
pub event_type: String,

3. Missing ExprTrait Import

Methods like .eq(), .like(), .contains() on Expr require the trait import in 2.0:

use sea_orm::ExprTrait; // required in 2.0

Expr::col((self.entity_name(), *self)).like(s)

4. Do Not Use Removed or Renamed APIs

1.0 (removed/renamed)	2.0 (correct)
.into_condition()	.into()
db.execute(Statement::from_sql_and_values(..))	db.execute_raw(Statement::from_sql_and_values(..))
db.query_all(backend.build(&query))	db.query_all(&query)
Alias::new("col") for static strings	Expr::col("col") directly
insert_many(..).on_empty_do_nothing()	insert_many([]) returns None safely

5. Do Not Manually impl Traits That DeriveValueType Generates

In 2.0, DeriveValueType auto-generates NotU8, IntoActiveValue, and TryFromU64. Remove manual implementations to avoid conflicts.

6. PostgreSQL: serial is No Longer Default

Auto-increment columns now use GENERATED BY DEFAULT AS IDENTITY. Use feature flag postgres-use-serial-pk for legacy behavior.

7. SQLite: Integer Type Mapping Changed

Both Integer and BigInteger map to integer in 2.0. Use sea-orm-cli --big-integer-type=i32 if needed.

For complete migration guide, see references/migration-guide.md.

Common Operations Quick Reference

Select

// Find all
let cakes: Vec<cake::Model> = Cake::find().all(db).await?;

// Filter
let chocolate: Vec<cake::Model> = Cake::find()
    .filter(Cake::COLUMN.name.contains("chocolate"))
    .all(db)
    .await?;

// Find by ID
let cheese: Option<cake::Model> = Cake::find_by_id(1).one(db).await?;

// Eager load related (1-1)
let cake_with_fruit: Vec<(cake::Model, Option<fruit::Model>)> =
    Cake::find().find_also_related(Fruit).all(db).await?;

// Eager load related (1-N and M-N)
let cake_with_fillings: Vec<(cake::Model, Vec<filling::Model>)> = Cake::find()
    .find_with_related(Filling)
    .all(db)
    .await?;

Insert

let apple = fruit::ActiveModel {
    name: Set("Apple".to_owned()),
    ..Default::default()
};

// Insert one
let apple = apple.insert(db).await?;

// Insert many
let result = Fruit::insert_many([apple, pear]).exec(db).await?;

Update

let pear: Option<fruit::Model> = Fruit::find_by_id(1).one(db).await?;
let mut pear: fruit::ActiveModel = pear.unwrap().into();

pear.name = Set("Sweet pear".to_owned());
let pear: fruit::Model = pear.update(db).await?;

// Bulk update
Fruit::update_many()
    .col_expr(fruit::COLUMN.cake_id, fruit::COLUMN.cake_id.add(2))
    .filter(fruit::COLUMN.name.contains("Apple"))
    .exec(db)
    .await?;

Delete

// Delete one
orange.delete(db).await?;

// Delete many
fruit::Entity::delete_many()
    .filter(fruit::COLUMN.name.contains("Orange"))
    .exec(db)
    .await?;

Feature Flags

Key feature flags to know:

• sqlx-mysql, sqlx-postgres, sqlx-sqlite - Database drivers
• runtime-tokio-native-tls, runtime-tokio-rustls - Async runtime
• with-chrono, with-time - Date/time libraries
• with-rust_decimal, with-bigdecimal - Decimal libraries
• with-json - JSON support
• entity-registry, schema-sync - Entity-first workflow
• postgres-use-serial-pk - Legacy PostgreSQL serial types

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references/entity-patterns.md

• Basic entity structure
• All relation types (Has-One, Has-Many, Many-to-Many, Self-referential)
• Composite primary keys
• Custom types with DeriveValueType
• Column attributes reference

references/activemodel-patterns.md

• Creating ActiveModels (3 methods)
• Builder pattern usage
• Nested persistence examples
• Update patterns
• Insert vs Save semantics
• ActiveValue states

references/query-patterns.md

• Basic CRUD queries
• Filtering with strongly-typed columns
• Entity Loader API patterns
• Join operations
• Pagination
• Aggregation
• Raw SQL with parameter binding

references/migration-guide.md

• Complete 1.0 to 2.0 migration guide
• Breaking changes table
• API renames reference
• Step-by-step migration instructions

This skill provides comprehensive coverage of SeaORM 2.0 with focus on the new patterns and critical anti-patterns to avoid.

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Source: FlyinPancake/yoink — distributed by TomeVault.