TypeORM Attempts to create tables that already exist
Problem
Issue type: [ ] question [x ] bug report [ ] feature request [ ] documentation issue Database system/driver: [ ] `cordova` [ ] `mongodb` [x ] `mssql` [ ] `mysql` / `mariadb` [ ] `oracle` [ ] `postgres` [ ] `sqlite` [ ] `sqljs` [ ] `react-native` [ ] `expo` TypeORM version: [ x] `latest` [ ] `@next` [ ] `0.x.x` (or put your version here) Steps to reproduce or a small repository showing the problem: If I delete all the tables in my database and run my app, all tables are created successfully. If I then stop the app and restart it, typeorm attempts to create tables that already exist and then fails. Here is the output from TypeOrm for the second run: Here is the beginning of the definition for the EmployeeAvailabilities table (there are more columns than this): [code block] At first I thought the issue was because the class name and table name do not match. But if I make the class name and table name match, the issue still occurs.
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1 Fix
Prevent TypeORM from Attempting to Create Existing Tables
TypeORM may attempt to synchronize the database schema on every application start, which can lead to errors if the tables already exist. This behavior is influenced by the `synchronize` option in the TypeORM configuration, which defaults to true. If the application tries to create tables that are already present in the database, it will throw an error.
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- 1
Check TypeORM Configuration
Ensure that the TypeORM configuration does not have the `synchronize` option set to true if you are managing the database schema manually.
typescriptconst connectionOptions = { type: 'mssql', host: 'localhost', username: 'user', password: 'password', database: 'db', synchronize: false }; - 2
Use Migrations for Schema Changes
Instead of relying on automatic schema synchronization, create and run migrations to manage database schema changes. This will prevent TypeORM from trying to create existing tables.
bashtypeorm migration:generate -n MigrationName typeorm migration:run - 3
Verify Existing Tables
Before running the application, manually check the database to ensure that the required tables exist. If they do not, you can create them using the generated migration or manually.
sqlSELECT * FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME = 'EmployeeAvailabilities'; - 4
Handle Errors Gracefully
Implement error handling in your application to catch and log errors related to table creation. This will help diagnose issues if they arise again in the future.
typescripttry { await connection.synchronize(); } catch (error) { console.error('Error during schema synchronization:', error); }
Validation
After applying these changes, restart the application and confirm that no errors related to existing tables are thrown. Check the application logs to ensure that the database schema is managed correctly without attempts to recreate existing tables.
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Submitted by
Alex Chen
2450 rep