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2020-06-14 Magento2

Magento 2 Database And Models

Magento 2 Fundamentals: Db and Models#

Databases#

ORM - Object-relational mapping, technique to access a relational database from an oo language

Magento ORM:

  • models - data + behaviour / entities
  • resource models - Data mappers for storage structure
  • collections - model sets and related functionality (soring, paging)
  • Resources - database connectors via adapters

Only models contain and manipulate data

Models encapsulate storage independent business logic. contain deprecated CRUD methods: load(), save(), delete() that delegate to the resource model. Best practice: models should be passed directly to CRUD methods on resource models. Model cannot access db directly.

Resource models - storage related logic. Uses db adapter.

Advantages:

  • decouple business logic from the storage layer
  • Decouple storage schema from DB driver implementation (Data mapper)

Resource collections - list of models of a specific type

Resource models access the database through \Magento\Framework\Db\Adapter\Pdo and Zend_Db

Model-to-Resource Model#

When creating a new model , it needs to know which resource model to us. Class name is specified using _init() method in _construct(). Which is required to support the inherited AbstractModel methods getResource() and getCollection()

To create a model, create a class and extend from \Magento\Framework\Model\AbstractModel

You no longer need to declare the model, resource model, adapters and other config.

Use the _init single underscore, not the real double underscore PHP constructor. The _construct is also legacy from Magento 1 and is called by the real __construct() method.

Resource Model-To-Database#

Extends: \Magento\Framework\Model\ResourceModel\Db\AbstractDb

Need to define table name and primary key.

Collection-To-Model#

Extends: Magento\Framework\Model\Framework\Model\ResourceModel\Db\Collection\AbstractCollection

Need to specify which model it corresponds to and a matching resource model

Models#

Not all models are storage persistent. No need for models only in /Models directory. You can put them anywhere.

Model Type Interfaces - Declare setters and getters for API

Magento 2 models inherit automatically fired events: _eventPrefix and _eventObject

Resoure Models#

Load, save and delete data

ResourceConnection module (Enterprise edition) provides features to split the database by functionality for higher scalability.

Collections#

Collections have sorting etc and Lazy load

Close to the DB layer

Main issues it solves:

  • Container for storing collections of objects
  • Prevents unnecessary data loading
  • Stores all objects during a session
  • Provides an interface for filtering and sorting entities

eg: array("lteq" => 'uk_')

Models#

CRUD workflow - reading#

$resourceModel->load($model, $id, $field = null)

  • Requires an argument for retrieving records
  • Always returns an object instance
  • 2nd argument to select record based on property or column name

Categories and products (EAV based) can be loaded using loadByAttribute($attribute, $value, $additionalAttributes = '*')

$model->_beforeLoad() deprecated, better to use plugins into resource model

Difference between read/write adapters has been eliminated

$model->afterLoad()

$model->updateStoredData()

$_hasDataChanged

$resourceModel->save()

$model->isDeleted()

$model->hasDataChenged()

$model->validateBeforeSave()

$model->beforeSave()

$model->beforeDelete()

$model->afterDelete()

$model->afterDeleteCommit()

isSaveAllowed(), checks _dataSaveAllowed

$model->afterSave()

These all use $resourceModel now:

$resourceModel->save($model)

$resourceModel->load($model, $id, $field = null)

$resourceModel->delete($model)

Setup Scripts and Setup Resources#

Setup scripts are powerful to do db customisations and for setting configurations

Once magento runs the isntall script it woll never run it again, you need to write update scripts.

Module version is set in the module.xml: setup_version attribute

Processed module versions are registered in setup_module table

Check module status: run bin/magento module:status

Install script#

Syntax is the same as magento 1

Data setup scripts#

Split data setup with data by using data setup scripts.

Are run after all schema setup scripts are completed.

$context gives some information about the current module version

Module version status: bin/magento setup:db:status

code#

Needs:

$installer->startSetup();
$installer->endSetup();

2 ways to apply changes:

  • run(): executes plain sequentially (Db specific)
  • $installer->getConnection() : Using DDL operations through adapter

EAV#

EAV entity is an entity type that is persisted using the EAV database schema via the EAV resource model

  • EAV based entity models also extend Magento\Framework\Model\AbstractModel, just like flat table entity models.
  • EAV based resource models extend Magento\Eav\Model\Entity\AbstractEntity, rather than \Magento\Framework\Model\Resource\Db\AbstractDb

Resource methods#

Additional methods:

  • getAttribute(): $product->getResource()->getAttribute('color')
  • saveAttribute(): $product->setWeight(1.99)->getResource()->saveAttribute($product, 'weight');
  • getWriteConnection(): Interface to write adapter, read connection
  • getEntityTable(): Contract to getMainTable(), EAV models implement getEntityTable()

No difference declaring EAV based entity models

Declaring EAV resource models differ from flat table. Instead of initialising the resource model with the main table name and primary key column. EAV resource models are intialised with the entity type code and the name of the DB connection resource to use.

Any additional data is read from eav_entity_type table

EAV load process#

2 aspects:

  • Managing relationships
  • Managing content
  1. Loads meta of the EAV
  2. Concrete attribute values

For select/multi-select attributes: Magento 2 uses the table source model. Loaded from eav_attribute_option and eav_attribute_option_value

Collection load specific method#
  • addAttributeToSelect() - Adds the attributes value table to select and attribute to result
  • addAttribute ToFilter() - Joins the attribute table specific for this attribute and adds a filter condition
  • joinAttribute() - Joins a value table ffrom an attribute from another entity
Saving EAV Structure#

Similar to flat table except one additional layer beforeSave() and afterSave() calls the attrbiute backend model.

Backend Type*:

  • static: entity
  • varchar: entity_varchar
  • int: entity_int
  • decimal: entity_decimal

Loading or saving from a specific ou use getTable()

Eg. $product->getResource()->getAttribute($attributeCode)->getBackend()->getTable()

Attribute Management#

entity_type specific properties are saved in catalog_eav_attribute

  • attribute_id: Unique id from the eav_attribute table
  • entity_type_id: ID of associated entity type
  • attribute_code: unique for entity type
  • attribute_model: optional alternate model to use
  • backend_model
  • frontend_model
  • frontend_input
  • frontend_label
  • frontend_class
  • is_required
  • default_value

Two aspects of EAV#

Meta information: Entity type, Attributes amd Attribute set and groups Content: Entity records, Attribute values

With the Magento\Eav\Model\Config class you can get info:

  • getAttribute($entityType, $attributeCode) - get an attribute instance
  • getEntityType($entityTypeCode) - Return the entity type instance
Standard attribute types#
  • varchar
  • text
  • int
  • decimal
  • datetime

Two examples of the methods that the Setup class implements are addAttribute() and updateAttribute()

  • Creating a new table uses Setup/InstallSchema.php
  • Making product attribute visible in “more info” tab: visible_on_front
  • Class type to fetch multiple records: Collection
  • Add new product attribute: Setup/InstallData.php
  • Add a where clause into query generated by collection object: addFieldToFilter()