loopback-connector-mysql

MySQL is a popular open-source relational database
management system (RDBMS). The loopback-connector-mysql module provides the
MySQL connector module for the LoopBack framework.

Installation

In your application root directory, enter this command to install the connector:

``sh
npm install loopback-connector-mysql --save
`

Note: The MySQL connector requires MySQL 5.0+.

This installs the module from npm and adds it as a dependency to the
application's package.json file.

If you create a MySQL data source using the data source generator as described
below, you don't have to do this, since the generator will run npm install for
you.

Creating a MySQL data source

For LoopBack 4 users, use the LoopBack 4
Command-line interface
to generate a DataSource with MySQL connector to your LB4 application. Run
lb4 datasource, it
will prompt for configurations such as host, post, etc. that are required to
connect to a MySQL database.

After setting it up, the configuration can be found under
src/datasources/.datasource.ts, which would look like this:

`ts
const config = {
name: 'db',
connector: 'mysql',
url: '',
host: 'localhost',
port: 3306,
user: 'user',
password: 'pass',
database: 'testdb',
};
`



For LoopBack 3 users

Use
the Data source generator to
add a MySQL data source to your application.
The generator will prompt for the database server hostname, port, and other
settings required to connect to a MySQL database. It will also run the
npm install command above for you.

The entry in the application's /server/datasources.json will look like this:

`javascript
"mydb": {
"name": "mydb",
"connector": "mysql",
"host": "myserver",
"port": 3306,
"database": "mydb",
"password": "mypassword",
"user": "admin"
}
`





Edit .datasources.ts to add any other additional properties
that you require.

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Property	Type	Description
collation	String	Determines the charset for the connection. Default is utf8_general_ci.
connector	String	Connector name, either “loopback-connector-mysql” or “mysql”.
connectionLimit	Number	The maximum number of connections to create at once. Default is 10.
database	String	Database name
debug	Boolean	If true, turn on verbose mode to debug database queries and lifecycle.
host	String	Database host name
password	String	Password to connect to database
port	Number	Database TCP port
socketPath	String	The path to a unix domain socket to connect to. When used host and port are ignored.
supportBigNumbers	Boolean	Enable this option to deal with big numbers (BIGINT and DECIMAL columns) in the database. Default is false.
timeZone	String	The timezone used to store local dates. Default is ‘local’.
url	String	Connection URL of form mysql://user:password@host/db. Overrides other connection settings.
username	String	Username to connect to database

NOTE: In addition to these properties, you can use additional parameters
supported by node-mysql.

Type mappings

See LoopBack 4 types (or LoopBack 3 types) for
details on LoopBack's data types.

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LoopBack Type	MySQL Type
String/JSON	VARCHAR
Text	TEXT
Number	INT
Date	DATETIME
Boolean	TINYINT(1)
GeoPoint object	POINT
Custom Enum type (See Enum below)	ENUM

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MySQL Type	LoopBack Type
CHAR	String
BIT(1) CHAR(1) TINYINT(1)	Boolean
VARCHAR TINYTEXT MEDIUMTEXT LONGTEXT TEXT ENUM SET	String
TINYBLOB MEDIUMBLOB LONGBLOB BLOB BINARY VARBINARY BIT	Node.js Buffer object
TINYINT SMALLINT INT MEDIUMINT YEAR FLOAT DOUBLE NUMERIC DECIMAL	Number For FLOAT and DOUBLE, see Floating-point types. For NUMERIC and DECIMAL, see Fixed-point exact value types
DATE TIMESTAMP DATETIME	Date

_NOTE_ as of v3.0.0 of MySQL Connector, the following flags were introduced:

- treatCHAR1AsString default false - treats CHAR(1) as a String instead of a
Boolean
- treatBIT1AsBit default true - treats BIT(1) as a Boolean instead of a
Binary
- treatTINYINT1AsTinyInt default true - treats TINYINT(1) as a Boolean
instead of a Number

Data mapping properties

Except the common database-specific properties we introduce in How LoopBack Models Map To Database Tables/Collections, the following are more detailed examples and MySQL-specific settings.

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Besides the basic LoopBack types, as we introduced above, you can also specify
additional MySQL-specific properties for a LoopBack model. It would be mapped to
the database.

Use the mysql. in the model definition or the property definition to
configure the table/column definition.

For example, the following settings would allow you to have custom table name
(Custom_User) and column name (custom_id and custom_name). Such mapping is
useful when you'd like to have different table/column names from the model:

{% include code-caption.html content="user.model.ts" %}

`ts
@model({
settings: { mysql: { schema: 'testdb', table: 'Custom_User'} },
})
export class User extends Entity {
@property({
type: 'number',
required: true,
id: true,
mysql: {
columnName: 'custom_id',
},
})
id: number;

@property({
type: 'string',
mysql: {
columnName: 'custom_name',
},
})
name?: string;
`



For LoopBack 3 users

`javascript
{
"name": "User",
"options": {
"mysql": {
"schema": "testdb",
"table": "Custom_User"
}
},
"properties": {
"id": {
"type": "Number",
"required": true,
"mysql": {
"columnName": "custom_id",
}
},
"name": {
"type": "String",
"mysql": {
"columnName": "custom_name",
}
},
}
}
`



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Except the names, you can also use the dataType column/property attribute to
specify what MySQL column type to use. The following MySQL type-dataType
combinations are supported:

- number
- integer
- tinyint
- smallint
- mediumint
- int
- bigint
- float
- double
- decimal

The following examples will be in LoopBack 4 style, but it's the same if you
provide mysql. to the LB3 property definition.

#### Floating-point types

For Float and Double data types, use the precision and scale options to
specify custom precision. Default is (16,8).



Example

`ts
@property({
type: 'Number',
mysql: {
dataType: 'float',
precision: 20,
scale: 4
}
})
price: Number;
`





#### Fixed-point exact value types

For Decimal and Numeric types, use the precision and scale options to
specify custom precision. Default is (9,2). These aren't likely to function as
true fixed-point.



Example

`ts
@property({
type: 'Number',
mysql: {
dataType: 'decimal',
precision: 12,
scale: 8
}
})
price: Number;
`



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Convert String / DataSource.Text / DataSource.JSON to the following MySQL types:

- varchar
- char
- text
- mediumtext
- tinytext
- longtext

Example

`ts
@property({
type: 'String',
mysql: {
dataType: 'char',
dataLength: 24 // limits the property length
},
})
userName: String;
`



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Convert JSON Date types to datetime or timestamp.

Example

`ts
@property({
type: 'Date',
mysql: {
dataType: 'timestamp',
},
})
startTime: Date;
`



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See the Model ENUM property for details.

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Use the default and dataType properties to have MySQL handle setting column DEFAULT value.



Example

`ts
@property({
type: 'String',
mysql: {
dataType: 'varchar',
default: 'pending'
}
})
status: String;

@property({
type: 'Number',
mysql: {
dataType: 'int',
default: 42
}
})
maxDays: Number;

@property({
type: 'boolean',
mysql: {
dataType: 'tinyint',
default: 1
}
})
isDone: Boolean;
`





For the date or timestamp types use CURRENT_TIMESTAMP or now.



Example

`ts
@property({
type: 'Date',
mysql: {
dataType: 'datetime',
default: 'CURRENT_TIMESTAMP'
}
})
last_modified: Date;
`



NOTE: The following column types do NOT supported
MySQL Default Values:

- BLOB
- TEXT
- GEOMETRY
- JSON

Discovery and auto-migration

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The MySQL connector supports _model discovery_ that enables you to create
LoopBack models based on an existing database schema. Once you defined your
datasource:

- LoopBack 4 users could use the commend
lb4 discover to
discover models.
- For LB3 users, please check
Discovering models from relational databases.
(See
database discovery API
for related APIs information)

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The MySQL connector also supports _auto-migration_ that enables you to create a
database schema from LoopBack models. For example, based on the following model,
the auto-migration method would create/alter existing Customer table in the
database. Table Customer would have two columns: name and id, where id
is also the primary key that has auto_increment set as it has definition of
type: 'Number' and generated: true:

`ts
@model()
export class Customer extends Entity {
@property({
id: true,
type: 'Number',
generated: true,
})
id: number;

@property({
type: 'string',
})
name: string;
}
`

Moreover, additional MySQL-specific properties mentioned in the
Data mapping properties section work with
auto-migration as well.

#### Auto-generated ids

For now LoopBack MySQL connector only supports auto-generated id
(generated: true) for integer type as for MySQL, the default id type is
_integer_. If you'd like to use other types such as string (uuid) as the id
type, you can:

- use uuid that is generated by your LB application by setting
defaultFn: uuid.

`ts
@property({
id: true,
type: 'string'
defaultFn: 'uuidv4',
// generated: true, -> not needed
})
id: string;
`

- Alter the table in your database to use a certain function if you prefer
having the database to generate the value.

`ts
@property({
id: true,
type: 'string'
generated: true, // to indicate the value generates by the db
useDefaultIdType: false, // needed
})
id: string;
`

#### Auto-migrate/Auto-update models with foreign keys

Foreign key constraints can be defined in the model definition.

Note: The order of table creation is important. A referenced table must
exist before creating a foreign key constraint. The order can be specified
using the optional SchemaMigrationOptions argument of migrateSchema:

`
await app.migrateSchema({
models: [ 'Customer', 'Order' ]
});
`

Define your models and the foreign key constraints as follows:

{% include code-caption.html content="customer.model.ts" %}

`ts
@model()
export class Customer extends Entity {
@property({
id: true,
type: 'Number',
generated: true,
})
id: number;

@property({
type: 'string',
})
name: string;
}
`

order.model.ts:

`ts
@model({
settings: {
foreignKeys: {
fk_order_customerId: {
name: 'fk_order_customerId',
entity: 'Customer',
entityKey: 'id',
foreignKey: 'customerId',
},
},
})
export class Order extends Entity {
@property({
id: true,
type: 'Number',
generated: true
})
id: number;

@property({
type: 'string'
})
name: string;

@property({
type: 'Number'
})
customerId: number;
}
`



For LoopBack 3 users

`json
({
"name": "Customer",
"options": {
"idInjection": false
},
"properties": {
"id": {
"type": "Number",
"id": 1
},
"name": {
"type": "String",
"required": false
}
}
},
{
"name": "Order",
"options": {
"idInjection": false,
"foreignKeys": {
"fk_order_customerId": {
"name": "fk_order_customerId",
"entity": "Customer",
"entityKey": "id",
"foreignKey": "customerId"
}
}
},
"properties": {
"id": {
"type": "Number"
"id": 1
},
"customerId": {
"type": "Number"
},
"description": {
"type": "String",
"required": false
}
}
})
`





MySQL handles the foreign key integrity by the referential action specified by
ON UPDATE and ON DELETE. You can specify which referential actions the
foreign key follows in the model definition upon auto-migrate or auto-update
operation. Both onDelete and onUpdate default to restrict.

Take the example we showed above, let's add the referential action to the
foreign key customerId:

`ts
@model({
settings: {
foreignKeys: {
fk_order_customerId: {
name: 'fk_order_customerId',
entity: 'Customer',
entityKey: 'id',
foreignKey: 'customerId',
onUpdate: 'restrict', // restrict|cascade|set null|no action|set default
onDelete: 'cascade' // restrict|cascade|set null|no action|set default
},
},
})
export class Order extends Entity {
...
`



For LoopBack 3 users

model-definiton.json

`json
{
"name": "Customer",
"options": {
"idInjection": false
},
"properties": {
"id": {
"type": "Number",
"id": 1
},
"name": {
"type": "String",
"required": false
}
}
},
{
"name": "Order",
"options": {
"idInjection": false,
"foreignKeys": {
"fk_order_customerId": {
"name": "fk_order_customerId",
"entity": "Customer",
"entityKey": "id",
"foreignKey": "customerId",
"onUpdate": "restrict",
"onDelete": "cascade"
}
}
},
"properties": {
"id": {
"type": "Number"
"id": 1
},
"customerId": {
"type": "Number"
},
"description": {
"type": "String",
"required": false
}
}
}
`

boot-script.js

`js
module.exports = function (app) {
var mysqlDs = app.dataSources.mysqlDS;
var Book = app.models.Order;
var Author = app.models.Customer;

// first autoupdate the Customer model to avoid foreign key constraint failure
mysqlDs.autoupdate('Customer', function (err) {
if (err) throw err;
console.log('\nAutoupdated table Customer.');

mysqlDs.autoupdate('Order', function (err) {
if (err) throw err;
console.log('\nAutoupdated table Order.');
// at this point the database table Order should have one foreign key customerId integrated
});
});
};
`





#### Breaking Changes with GeoPoint since 5.x

Prior to loopback-connector-mysql@5.x, MySQL connector was saving and loading
GeoPoint properties from the MySQL database in reverse. MySQL expects values to
be POINT(X, Y) or POINT(lng, lat), but the connector was saving them in the
opposite order(i.e. POINT(lat,lng)).

Use the geopoint type to achieve so:

`ts
@property({
type: 'geopoint'
})
name: GeoPoint;
`

If you have an application with a model that has a GeoPoint property using
previous versions of this connector, you can migrate your models using the
following programmatic approach:



Click here to expand

NOTE Please back up the database tables that have your application data
before performing any of the steps.

1. Create a boot script under server/boot/ directory with the following:

`js
'use strict';
module.exports = function (app) {
function findAndUpdate() {
var teashop = app.models.teashop;
//find all instances of the model we'd like to migrate
teashop.find({}, function (err, teashops) {
teashops.forEach(function (teashopInstance) {
//what we fetch back from the db is wrong, so need to revert it here
var newLocation = {
lng: teashopInstance.location.lat,
lat: teashopInstance.location.lng,
};
//only update the GeoPoint property for the model
teashopInstance.updateAttribute('location', newLocation, function (
err,
inst,
) {
if (err) console.log('update attribute failed', err);
else console.log('updateAttribute successful');
});
});
});
}

findAndUpdate();
};
`

2. Run the boot script by simply running your application or node .

For the above example, the model definition is as follows:

`json
{
"name": "teashop",
"base": "PersistedModel",
"idInjection": true,
"options": {
"validateUpsert": true
},
"properties": {
"name": {
"type": "string",
"default": "storename"
},
"location": {
"type": "geopoint"
}
},
"validations": [],
"relations": {},
"acls": [],
"methods": {}
}
`



Running tests

>> DO Remember to set the OS Timezone as UTC for the MYSQL DB and Unittest running environment. And DO NOT pass the MYSQL_DATABASE

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If you have a local or remote MySQL instance and would like to use that to run
the test suite, use the following command:

- Linux

`bash
MYSQL_HOST= MYSQL_PORT= MYSQL_USER= MYSQL_PASSWORD= MYSQL_DATABASE= CI=true npm test
`

- Windows

`bash
SET MYSQL_HOST= SET MYSQL_PORT= SET MYSQL_USER= SET MYSQL_PASSWORD= SET MYSQL_DATABASE= SET CI=true npm test
`

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If you do not have a local MySQL instance, you can also run the test suite with
very minimal requirements.

- Assuming you have Docker
installed, run the following script which would spawn a MySQL instance on your
local:

`bash
source setup.sh
`

where , , , and are optional
parameters. The default values are localhost, 3306, root, pass and
testdb respectively.

- Run the test:

`bash
npm test
``