quaerateum
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Simple typescript ORM for node.js based on data-mapper, unit-of-work and identity-map patterns. Supports MongoDB, MySQL, PostgreSQL and SQLite databases as well as usage with vanilla JS.
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# Creating custom driver
If you want to use database that is not currently supported, you can implement your own driver.
To do so, you will need to design 4 classes:
## Platform
Platform is a class that provides information about available features of given driver:
```typescript
import { Platform } from 'mikro-orm';
export class MyCustomPlatform extends Platform {
protected abstract schemaHelper: MyCustomSchemaHelper;
// here you can override default settings
usesPivotTable(): boolean;
supportsTransactions(): boolean;
supportsSavePoints(): boolean;
getNamingStrategy(): { new (): NamingStrategy; };
getIdentifierQuoteCharacter(): string;
getParameterPlaceholder(index?: number): string;
usesReturningStatement(): boolean;
normalizePrimaryKey<T = number | string>(data: IPrimaryKey): T;
denormalizePrimaryKey(data: IPrimaryKey): IPrimaryKey;
getSerializedPrimaryKeyField(field: string): string;
}
```
## SchemaHelper
Part of platform is a `SchemaHelper`, that provides information about how to build schema.
```typescript
import { SchemaHelper } from 'mikro-orm';
export class MyCustomSchemaHelper extends SchemaHelper {
// here you can override default settings
getIdentifierQuoteCharacter(): string;
getSchemaBeginning(): string;
getSchemaEnd(): string;
getSchemaTableEnd(): string;
getAutoIncrementStatement(meta: EntityMetadata): string;
getPrimaryKeySubtype(meta: EntityMetadata): string;
getTypeDefinition(prop: EntityProperty, types?: Record<string, string>, lengths?: Record<string, number>): string;
getUnsignedSuffix(prop: EntityProperty): string;
supportsSchemaConstraints(): boolean;
supportsSchemaMultiAlter(): boolean;
supportsSequences(): boolean;
quoteIdentifier(field: string): string;
dropTable(meta: EntityMetadata): string;
indexForeignKeys(): boolean;
}
```
## Connection
Next part is connection wrapper, that will be responsible for querying the database:
```typescript
import { Connection } from 'mikro-orm';
export class MyCustomConnection extends Connection {
// implement abstract methods
connect(): Promise<void>;
isConnected(): Promise<boolean>;
close(force?: boolean): Promise<void>;
getDefaultClientUrl(): string;
execute(query: string, params?: any[], method?: 'all' | 'get' | 'run'): Promise<QueryResult | any | any[]>;
}
```
## Driver
Last part is driver, that is responsible for using the connection to persist changes to
database. If you are building SQL driver, it might be handy to extend `AbstractSqlDriver`,
if not, extend `DatabaseDriver` abstract class.
If you want to have absolute control, you can implement the whole driver yourself via
`IDatabaseDriver` interface.
```typescript
import { DatabaseDriver } from 'mikro-orm';
export class MyCustomSchemaHelper extends DatabaseDriver {
// initialize connection and platform
protected readonly connection = new MyCustomConnection(this.config);
protected readonly platform = new MyCustomPlatform;
// and implement abstract methods
find<T extends IEntity>(entityName: string, where: FilterQuery<T>, populate?: string[], orderBy?: Record<string, QueryOrder>, limit?: number, offset?: number): Promise<T[]>;
findOne<T extends IEntity>(entityName: string, where: FilterQuery<T> | string, populate: string[]): Promise<T | null>;
nativeInsert<T extends IEntityType<T>>(entityName: string, data: EntityData<T>): Promise<QueryResult>;
nativeUpdate<T extends IEntity>(entityName: string, where: FilterQuery<IEntity> | IPrimaryKey, data: EntityData<T>): Promise<QueryResult>;
nativeDelete<T extends IEntity>(entityName: string, where: FilterQuery<IEntity> | IPrimaryKey): Promise<QueryResult>;
count<T extends IEntity>(entityName: string, where: FilterQuery<T>): Promise<number>;
}
```