Schema Migrations

Overview

SchemaLang automatically generates migration files when struct versions change, embedding migration SQL directly in generated code.

Struct Versioning

Add versions using semantic versioning:

struct User: version(1.2.0) {
    int64: id: primary_key: required: auto_increment: 
        description("User ID");
    string: username: required: 
        description("Username");
}

Version format: major.minor.patch

Automatic Migration Generation

Enable with -migrationsPath:

./SchemaLangTranspiler \
    -schema=./schemas \
    -outputDirectory=./output \
    -migrationsPath=./migrations \
    -cpp -sqlite

SchemaLang automatically creates migration files when versions change.

Embedded Migrations

Migrations are embedded in generated code as functions:

std::string SQLiteDB::migrate_User_1_0_0_to_1_1_0() {
    return R"SQL(
        ALTER TABLE User ADD COLUMN email VARCHAR(255);
        UPDATE User SET email = '';
    )SQL";
}

Auto-applied on database connect—no runtime migration files needed!

Migration Workflow

1. Update schema and increment version
2. Run transpiler with -migrationsPath
3. Migration files generated automatically
4. Recompile application
5. Migrations apply automatically on next database connection