Anyone who has ever used Magento 1 or Magento 2 knows about such feature as index. It really is very important and useful since everything that is viewed on the frontend relates to index. Indexing by itself is a fairly long process that is why incomplete index has been available almost because the first version of Magento. Partial index means that people index not the complete file but only the part that has been modified.
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In Magento 2 EE there can be found 2 indexing settings: Update on Save and Update by Schedule. You could configure each function under Tools -> System -> Index Management. All of them has its own advantages and disadvantages. The main benefit of the Update on Save setting is the fact it enables you to index data after saving the document. In other words, once you save a product in a category it becomes instantly on the frontend with all the current changes that you have applied. However, the primary disadvantage is the fact it incredibly increases the time for each and every operation to complete. That is why, to speed up the process there's been introduced the Update by Schedule setting. This feature enables you to index data in the backdrop so there is absolutely no hold off when you make an effort to save any record. Everything is performed asynchronously. The only minus of the method is that it could really have a while before cron job starts off indexing.
In this article we are going to describe how partial index works. Let's assume our default setting is Revise by Program, so, if not mentioned often, the below information will concern exactly this method.
There is absolutely no special devote the Magento code where you can find incomplete index entities principles. The whole reasoning of partial index is conducted in a databases - via MySQL causes if to be more specific. For instance, the catalog_product_entity desk contains 3 causes for the following incidents: AFTER Add, AFTER Revise, AFTER DELETE
Let’s check the trigger for the AFTER INSERT event:
As seen from the above code the trigger creates a record in the *_cl tables in regards to a new entity. Let's check one particular *_cl tables. They are all identical, so, what's true for just one of them is also true for the others. Each table consists of 2 areas: version_id and entity_id. The version_id field signifies the existing changes version amount, as the entity_id field shows the ids of the entities which have to be indexed.
When indexing is began by the cron job, the version_id principles in the *_cl furniture are compared to the information from the mview_talk about table which contains the information about index variants and index position. In the code side the logic is controlled by the Mview component which is a area of the Magento framework.
The cron job phone calls the \Magento\Framework\Mview\View::update method that phone calls the mandatory index. Let's have a look at this method somewhat closer:
For each index there is established another Mview class object that is responsible for index update.
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Let's see the actual parameters from the above code are a symbol of:
- $currentVersionId - reveals the current version of the version_id field in the *_cl stand;
- $lastVersionId - is the previous version of the equivalent index, extracted from the mview_express table;
- $ids - will be the ids of the entities that need to be indexed.
From then on, each index becomes partly re-indexed in its way. Now let's see if it's possible to add custom causes to MySQL dining tables and perform custom partial indexing. Let's check the \Magento\Framework\Mview\View::subscribe method:
The first brand verifies whether incomplete indexing is allowed for the Mview index. Next, there is established a respected *_cl table. From then on the cycle goes through the set of all users and creates causes in the MySQL stand. To add a custom view that will keep track of for changes in your Mview index furniture you just need to generate an mview.xml data file in the module directory.
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Let's describe one at a time what each debate is in charge of. For example, let's take a code test from the component Catalog-Permission:
This code creates the catalogpermissions_category_cl table which is subscribed for changes in catalog_category_entity and catalog_category_entity_int desks' data. The info from entity_column - entity_identification will be sent to the *_cl stand. This will lead to the triggers of the following type:
Re-indexing will be performed by the thing of the class field (start to see the $action changing in the aforementioned code). Nevertheless, you might have pointed out that we haven't used the membership_model field. This feature is noted in the <table> field and this implies the course which is responsible for creating sets off and their syntax. Certain sets off might not be as simple as identified above. In such instances one needs to use a custom model that is inherited from the default one. Here is an example of such a model from Magento 2 EE:
When you see, your body of the cause differs from the cause which we created the very first time.
From the above example you might observe how simple and beautiful a partial index is. You are able to redefine existing subscriptions without the problems (there have been such conditions with the EE version when the designers simply forgot about the Staging module) as well as define your own subscriptions to work with custom indexes.