Create Staging.md

Author: unicoder88

xx. Magento Commerce Features/Staging.md

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+# Magento 2 Staging
+
+## High level staging implementation overview
+
+- Future editions of products/categories etc. are saved as a copy with a timestamped from-to columns.
+- Current staging version is saved as a flag, used in all collections to add WHERE condition
+- You can browse (preview) frontend site seeing future versions passing version and signature GET parameters
+
+
+## Demonstrate an understanding of the events processing flow
+
+Influence of Staging on the event processing.
+
+What is a modification of the event processing mechanism introduced by the staging module?
+
+
+\Magento\Staging\Model\Event\Manager:
+
+- ban some events in preview mode - none by default
+- ban some observers in preview mode
+
+  - `catalog_category_prepare_save`
+  - `catalog_category_save_after`
+  - `catalog_category_save_before`
+  - `catalog_category_move_after`
+
+
+## DB collection flag `disable_staging_preview`
+
+- connection->select()
+- \Magento\Framework\DB\Adapter\Pdo\Mysql::select
+- Magento\Framework\DB\SelectFactory::create
+- Magento\Framework\DB\Select\SelectRenderer
+- // work with select...
+- \Magento\Framework\DB\Select::assemble
+- \Magento\Framework\DB\Select\SelectRenderer::render
+  - \Magento\Framework\DB\Select\FromRenderer
+  - \Magento\Staging\Model\Select\FromRenderer
+
+
+```
+from = [
+    flag = [
+        joinType = 'from'
+        tableName = 'flag'
+    ]
+]
+```
+
+```
+$select->where($alias . '.created_in <= ?', $versionId);
+$select->where($alias . '.updated_in > ?', $versionId);
+```
+
+Only known staged tables are affected - \Magento\Staging\Model\StagingList::getEntitiesTables - `*_entity`
+
+
+## Staging modification to the Magento database operations (row_id, entity managers)
+
+Flow modifications introduced by staging (triggers, row_id, data versions).
+
+- deletes foreign keys to removed entity_id column
+- creates foreign key to row_id
+- replaces indexes
+
+**Triggers** created differently! Attributes no longer have entity_id for `_cl` tables, so one more
+extra call to load entity_id by row_id is added to each update by schedule trigger.
+
+\Magento\Framework\Mview\View\Subscription::buildStatement
+vs
+\Magento\CatalogStaging\Model\Mview\View\Attribute\Subscription::buildStatement
+
+
+trg_catalog_product_entity_int_after_insert:
+```SQL
+-- before
+INSERT IGNORE INTO `catalog_product_flat_cl` (`entity_id`) VALUES (NEW.`entity_id`);
+-- after
+SET @entity_id = (SELECT `entity_id` FROM `catalog_product_entity` WHERE `row_id` = NEW.`row_id`);
+INSERT IGNORE INTO `catalog_product_flat_cl` (`entity_id`) values(@entity_id);
+```
+
+trg_catalog_product_entity_int_after_update:
+```SQL
+-- before
+IF (NEW.`value_id` <=> OLD.`value_id` OR NEW.`attribute_id` <=> OLD.`attribute_id` OR NEW.`store_id` <=> OLD.`store_id` OR NEW.`entity_id` <=> OLD.`entity_id` OR NEW.`value` <=> OLD.`value`) THEN INSERT IGNORE INTO `catalog_product_flat_cl` (`entity_id`) VALUES (NEW.`entity_id`); END IF;
+-- after
+SET @entity_id = (SELECT `entity_id` FROM `catalog_product_entity` WHERE `row_id` = NEW.`row_id`);
+IF (NOT(NEW.`value_id` <=> OLD.`value_id`) OR NOT(NEW.`attribute_id` <=> OLD.`attribute_id`) OR NOT(NEW.`store_id` <=> OLD.`store_id`) OR NOT(NEW.`value` <=> OLD.`value`) OR NOT(NEW.`row_id` <=> OLD.`row_id`)) THEN INSERT IGNORE INTO `catalog_product_flat_cl` (`entity_id`) values(@entity_id); END IF;
+```
+
+trg_catalog_product_entity_int_after_delete:
+```SQL
+-- before
+INSERT IGNORE INTO `catalog_product_flat_cl` (`entity_id`) VALUES (OLD.`entity_id`);
+-- after
+SET @entity_id = (SELECT `entity_id` FROM `catalog_product_entity` WHERE `row_id` = OLD.`row_id`);
+INSERT IGNORE INTO `catalog_product_flat_cl` (`entity_id`) values(@entity_id);
+```
+
+
+## sequence tables
+
+Staging migration scripts do this: `row_id` becomes auto_increment, and `entity_id` (`page_id` etc.) column
+is no longer auto incremented, but still required!
+
+Requests like `INSERT INTO cms_page (identified) VALUES("test_page")` would result in error because page_id
+is normally auto_increment and not passed in request.
+
+Magento fixes this by manually generating auto increments for entity_id in separate sequence tables.
+
+Exmple:
+
+- \Magento\Framework\Model\ResourceModel\Db\CreateEntityRow::prepareData
+- `$output[$metadata->getIdentifierField()] = $metadata->generateIdentifier();`
+- \Magento\Framework\EntityManager\Sequence\Sequence::getNextValue
+- insert and return next ID into `sequence_*` table
+
+`sequence_cms_page`, `sequence_catalog_category`, `sequence_catalogrule`, ...
+
+In community edition (no staging), `$metadata->generateIdentifier()` because sequenceTable is not passed.
+
+
+- \Magento\Framework\EntityManager\MetadataPool::getMetadata
+- \Magento\Framework\EntityManager\MetadataPool::createMetadata
+- new \Magento\Framework\EntityManager\EntityMetadata
+  - `sequence` argument: \Magento\Framework\EntityManager\Sequence\SequenceFactory::create:
+    - no staging - sequence = null
+    - staging defines `sequenceTable` - `new \Magento\Framework\EntityManager\Sequence\Sequence(connection, sequenceTable)`
+
+
+
+## Common staging plugins
+
+- FrontControllerInterface::beforeDispatch - validate `___version`, `___timestamp`, `___signature`
+- Magento\PageCache\Model\Config::afterIsEnabled - disabled in preview mode
+- Magento\Store\Model\BaseUrlChecker - disabled in preview mode
+- Magento\Framework\Stdlib\DateTime\Timezone::isScopeDateInInterval - interval never validated in preview mode
+- Magento\Store\Model\StoreResolver::getCurrentStoreId - use `___store` in preview mode
+- Magento\Customer\Model\Session::regenerateId, destroy - never regenerate/destroy in preview mode
+- getUrl - adds `___version`, `___store`, possibly `__timestamp`, `__signature` in preview mode
+- disables block_html caching
+
+
+## Staging-related modifications of the indexing process
+
+- plugin before Magento\Catalog\Controller\Category\View
+- \Magento\CatalogStaging\Model\Plugin\Controller\View::beforeExecute
+- \Magento\CatalogStaging\Model\Indexer\Category\Product\Preview::execute
+- \Magento\Catalog\Model\Indexer\Category\Product\AbstractAction::reindex
+
+Reindex using temporary tables with suffix `_catalog_staging_tmp`,
+e.g. `catalog_category_product_index_store1_catalog_staging_tmp`
+
+
+## Save staging update
+
+\Magento\SalesRuleStaging\Controller\Adminhtml\Update\Save::execute
+\Magento\Staging\Model\Entity\Update\Save::execute
+
+```
+staging[mode]: save
+staging[update_id]: 
+staging[name]: 3 September
+staging[description]: Everything is new
+staging[start_time]: 2020-09-03T07:00:00.000Z
+staging[end_time]: 
+```
+
+\Magento\Staging\Model\Entity\Update\Action\Pool::getAction(
+  entityType = 'Magento\SalesRule\Api\Data\RuleInterface',
+  namespace = 'save',
+  actionType = mode = 'save'
+)
+
+- \Magento\Staging\Model\Entity\Update\Action\Save\SaveAction:
+  - \Magento\Staging\Model\Entity\Update\Action\Save\SaveAction::createUpdate
+  - \Magento\Staging\Model\EntityStaging::schedule
+    - \Magento\CatalogRuleStaging\Model\CatalogRuleStaging::schedule
+      - validates intersecting updates
+      - sets `created_in`, saves entity model (catalog rule)
+- Magento\CatalogRuleStaging\Model\Rule\Hydrator
+- \Magento\CatalogRuleStaging\Model\Rule\Retriever::getEntity - $this->ruleRepository->get($entityId)
+
+
+## Preview
+
+All links are automatially updated:
+- \Magento\Framework\Url::getUrl
+- \Magento\Framework\Url\RouteParamsPreprocessorComposite::execute
+- \Magento\Staging\Model\Preview\RouteParamsPreprocessor::execute
+- `[_query][___version]=`, `[_query][___store]=`
+- `__timestamp=`, `__signature=`
+
+Example:
+
+vendor/magento/module-catalog/view/frontend/layout/default.xml:
+```XML
+<block class="Magento\Catalog\Block\FrontendStorageManager" name="frontend-storage-manager" before="-"
+       template="Magento_Catalog::frontend_storage_manager.phtml">
+    <arguments>
+        <!-- ... -->
+        <item name="updateRequestConfig" xsi:type="array">
+            <item name="url" xsi:type="serviceUrl" path="/products-render-info"/>
+        </item>
+```
+
+- \Magento\Store\Model\Argument\Interpreter\ServiceUrl::evaluate
+- https://m24ee.local/rest/default/V1/?___store=default&___version=1599422820&__signature=b5cd66d9ea383ea57356f28cf2dd0f8edeecbc516b4d7982f8aef2ce4bcd4d32&__timestamp=1599165421products-render-info
+
+
+URL examples:
+
+- REST - `?___version=`
+- category - `?update_id=`
+
+
+Preview from admin panel:
+
+- https://m24ee.local/admin/staging/update/preview/key/.../?preview_store=default&preview_url=https:/m24ee.local/&preview_version=1599116400
+  - header and iframe
+- https://m24ee.local/?___version=1599116400&___store=default&__timestamp=1599077245&__signature=a8f3a05adb92374873a3f9c4e1d36c1bddcc9748b32b046af4264b496243f95d
+
+
+\Magento\Staging\Plugin\Framework\App\FrontController::beforeDispatch - validate signature:
+
+```
+__signature = hash(sha256, "__version,__timestamp", secret key from env.php)
+```
+
+
+## Set current version
+
+\Magento\CatalogStaging\Model\Category\DataProvider::getCurrentCategory
+
+```
+$updateId = (int) $this->request->getParam('update_id');
+$this->versionManager->setCurrentVersionId($update->getId());
+```
+
+
+## checkout-staging
+
+- disable place order in preview
+- any quote, saved in preview mode, is saved in db table `quote_preview` and deleted by cron