{"id":16243,"date":"2018-07-10T14:29:43","date_gmt":"2018-07-10T12:29:43","guid":{"rendered":"https:\/\/belvg.com\/blog\/?p=16243"},"modified":"2021-02-18T09:24:06","modified_gmt":"2021-02-18T07:24:06","slug":"how-eav-data-storage-works-in-magento-2","status":"publish","type":"post","link":"https:\/\/belvg.com\/blog\/how-eav-data-storage-works-in-magento-2.html","title":{"rendered":"How EAV Data Storage Works in Magento 2"},"content":{"rendered":"\n

EAV (Entity-attribute-value) is a model of storing the values of entity attributes in a certain data storage. As a data storage, Magento 2 supports MySQL-compatible databases (like MySQL, MySQL NDB Cluster, MariaDB, Percona and others).<\/p>\n

The principles of EAV data storage work in Magento<\/a>
\nWhat happens when a new attribute is added to the system<\/a><\/p>\n

A table of the classical EAV model has 3 columns:<\/p>\n

    \n
  1. entity (the object to which you want to set the attribute value)<\/li>\n
  2. attribute<\/li>\n
  3. value<\/li>\n<\/ol>\n

    In the Flat<\/strong> model, the attribute values are stored in the same table as the entities, for each attribute, a separate column in the table is created.<\/p>\n

    In the EAV<\/strong> model, attribute values are stored in a separate table, where a separate column is not created for each attribute. For each attribute value of an entity, however, a new row is created in the EAV table.<\/p>\n

    <\/a>The principles of EAV data storage work in Magento<\/span><\/strong><\/h2>\n

    The differences between the classic EAV model and the one used by Magento:<\/span><\/p>\n

      \n
    1. Each attribute is assigned a backend type (varchar, int, text …).<\/li>\n
    2. Each type of EAV entities has a separate table. The types of EAV entities are stored in the eav_entity_type table. The name of the tables in which the entities are stored in the entity_table column.<\/li>\n
    3. System EAV entities are stored in the eav_entity table.<\/li>\n
    4. Attributes that have the backend type as static are stored in the same table as the entity. These attributes have a global scope.<\/li>\n
    5. Each backend type of each entity type has its own table, in which the attribute values are stored. The name of this table is constructed from the pattern {entity_table}_{backend_type}, where entity_table is the name of the entity table, and backend_type is the backend type of the attribute. These tables have the following columns: value_id (int), attribute_id (int), store_id ** (int), entity_id * (int), value (depending on the backend type).<\/li>\n<\/ol>\n

      Here is an image for illustrating the connections:<\/span><\/p>\n

      \"image5\"<\/a><\/p>\n

      In order to get\/write the attribute value, you need:<\/span><\/p>\n

        \n
      1. store_id**<\/li>\n
      2. entity_id*<\/li>\n
      3. entity_table or entity_type_id<\/li>\n
      4. attribute_id<\/li>\n<\/ol>\n
        <\/a>
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        If the entity_table is unknown, but you know the entity_type_id, then the entity_table can be obtained from the eav_entity_type table.<\/span><\/p>\n

        Magento gets the attributes values of the entity with one large SQL query, which is generated using the following algorithm:<\/span><\/p>\n

          \n
        1. Get all attribute tables for a particular entity_type.<\/span><\/li>\n
        2. For each table perform the following:<\/span>\n