How can I integrate NestJS ConfigService into a Drizzle custom column for encryption?

One common solution is to “externalize” the encryption key so that your encryption/decryption functions don’t need Nest’s DI at runtime. Instead of trying to inject ConfigService into Drizzle’s schema definitions (which aren’t created as part of the NestJS DI context), you can read and store the encryption key during application bootstrap and then reference that static value from your custom column.

Below are two approaches:

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1. Use a Global Configuration/Singleton

Create a separate module or singleton (e.g., an “EncryptionConfig” module) that is initialized in your NestJS bootstrap code. For example:

TYPESCRIPTCopied
// encryption.config.ts
export class EncryptionConfig {
  private static key: string;

  static initialize(key: string) {
    this.key = key;
  }

  static getKey(): string {
    if (!this.key) {
      throw new Error('Encryption key not initialized');
    }
    return this.key;
  }
}

Then in your NestJS bootstrap (or in the DrizzleModule provider factory), pull the key from ConfigService and initialize the singleton:

TYPESCRIPTCopied
// in your bootstrap or module initialization code
import { ConfigService } from '@nestjs/config';
import { EncryptionConfig } from './encryption.config';

async function bootstrap() {
  ...
  const configService = app.get(ConfigService);
  const encryptionKey = configService.get<string>('ENCRYPTION_KEY');
  EncryptionConfig.initialize(encryptionKey);
  ...
}

Now, in your Drizzle custom column definition, you can use the static method:

TYPESCRIPTCopied
// encrypted-column.ts
import { EncryptionConfig } from './encryption.config';
import { customType } from 'drizzle-orm';

export const encryptedColumn = customType<{ data: string }>({
  dataType() {
    return "text";
  },
  fromDriver(value: unknown) {
    const key = EncryptionConfig.getKey();
    // use key and perform decryption on value
    return decrypt(String(value), key);
  },
  toDriver(value: string) {
    const key = EncryptionConfig.getKey();
    // use key and perform encryption on value
    return encrypt(value, key);
  }
});

This approach avoids the DI issue by loading the configuration once, and then letting your encryption functions rely on that stored value.

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2. Pass the Encryption Key at Drizzle Initialization

If you’re defining your Drizzle integration in a provider, you can load the encryption key from the ConfigService there. Then, pass the key into any functions that build your schema definitions. This might look like:

TYPESCRIPTCopied
// drizzle-provider.ts
import { ConfigService } from '@nestjs/config';
import { drizzle } from 'drizzle-orm';
import * as DbSchema from './schema';
import { Pool } from 'pg';
import { EncryptionConfig } from './encryption.config';

export const DrizzleProvider = {
  provide: DrizzleModuleProvider,
  useFactory: async (configService: ConfigService) => {
    const encryptionKey = configService.get<string>('ENCRYPTION_KEY');
    // Initialize global encryption config or inject directly into your schema building functions
    EncryptionConfig.initialize(encryptionKey);

    const pool = new Pool({
      connectionString: configService.get<string>('DB_CONN_STRING'),
      ssl: {
        rejectUnauthorized: false
      },
    });

    const db = drizzle(pool, {
      schema: DbSchema,
    });
    return db;
  },
  inject: [ConfigService],
};

With this approach, any function or custom type within your schema can rely on the value injected during provider initialization (whether by a singleton or by a closure if you’re refactoring your schema building logic).

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Conclusion

Because your Drizzle entities aren’t themselves part of NestJS, you won’t be able to use dependency injection directly in the column definition. Instead, decouple your encryption key by loading it at startup (via NestJS ConfigService) and storing it in a globally accessible (or module-scoped) location. This is the least invasive, “least-hacky” way to integrate configuration data into non-DI-managed code.