wehub-resource-sync
77 lines
1.7 KiB
Markdown
77 lines
1.7 KiB
Markdown
# database-migration — additional patterns and templates
|
|
|
|
## Zero-Downtime Migrations
|
|
|
|
### Blue-Green Deployment Strategy
|
|
|
|
```javascript
|
|
// Phase 1: Make changes backward compatible
|
|
module.exports = {
|
|
up: async (queryInterface, Sequelize) => {
|
|
// Add new column (both old and new code can work)
|
|
await queryInterface.addColumn("users", "email_new", {
|
|
type: Sequelize.STRING,
|
|
});
|
|
},
|
|
};
|
|
|
|
// Phase 2: Deploy code that writes to both columns
|
|
|
|
// Phase 3: Backfill data
|
|
module.exports = {
|
|
up: async (queryInterface) => {
|
|
await queryInterface.sequelize.query(`
|
|
UPDATE users
|
|
SET email_new = email
|
|
WHERE email_new IS NULL
|
|
`);
|
|
},
|
|
};
|
|
|
|
// Phase 4: Deploy code that reads from new column
|
|
|
|
// Phase 5: Remove old column
|
|
module.exports = {
|
|
up: async (queryInterface) => {
|
|
await queryInterface.removeColumn("users", "email");
|
|
},
|
|
};
|
|
```
|
|
|
|
## Cross-Database Migrations
|
|
|
|
### PostgreSQL to MySQL
|
|
|
|
```javascript
|
|
// Handle differences
|
|
module.exports = {
|
|
up: async (queryInterface, Sequelize) => {
|
|
const dialectName = queryInterface.sequelize.getDialect();
|
|
|
|
if (dialectName === "mysql") {
|
|
await queryInterface.createTable("users", {
|
|
id: {
|
|
type: Sequelize.INTEGER,
|
|
primaryKey: true,
|
|
autoIncrement: true,
|
|
},
|
|
data: {
|
|
type: Sequelize.JSON, // MySQL JSON type
|
|
},
|
|
});
|
|
} else if (dialectName === "postgres") {
|
|
await queryInterface.createTable("users", {
|
|
id: {
|
|
type: Sequelize.INTEGER,
|
|
primaryKey: true,
|
|
autoIncrement: true,
|
|
},
|
|
data: {
|
|
type: Sequelize.JSONB, // PostgreSQL JSONB type
|
|
},
|
|
});
|
|
}
|
|
},
|
|
};
|
|
```
|