Issue #3463797 by mkalkbrenner: Avoid standard deletes when reindexin…

…g if the index is empty

src/Commands/SearchApiSolrCommands.php

@@ -270,6 +270,29 @@ public function indexParallel($indexId = NULL, array $options = ['threads' => NU
       }
       sleep(2);
     }
+
+    $this->commandHelper->resetEmptyIndexState([$indexId]);
+  }
+
+  /**
+   * Reset empty index state to FALSE.
+   *
+   * Important if drush search-api-solr:index-parallel crashed or has been
+   * interrupted. That might cause to block deletes on an index for one hour
+   * unless you run this command.
+   *
+   * @param string $indexId
+   *   (optional) A search index ID, or NULL to index items for all enabled
+   *   indexes.
+   * @param array $options
+   *   (optional) An array of options.
+   *
+   * @command search-api-solr:reset-empty-index-state
+   *
+   * @default $options []
+   */
+  public function resetEmptyIndexState($indexId = NULL, array $options = []) {
+    $this->commandHelper->resetEmptyIndexState([$indexId]);
   }
 
 }

src/Entity/Index.php

@@ -6,6 +6,8 @@
 
 class Index extends SearchApiIndex {
 
+  const KEEP_EMPTY_INDEX_STATE_SECONDS = 3600;
+
   /**
    * {@inheritdoc}
    */
@@ -19,4 +21,15 @@ public function getLockId(): string {
     return parent::getLockId();
   }
 
+  public function isIndexingEmptyIndex(): bool {
+    $key = "search_api.index.{$this->id()}.indexing_empty";
+    $timestamp = \Drupal::state()->get($key, 0);
+    return (\Drupal::time()->getRequestTime() - $timestamp) < self::KEEP_EMPTY_INDEX_STATE_SECONDS;
+  }
+
+  public function setIndexingEmptyIndex(bool $state): void {
+    $key = "search_api.index.{$this->id()}.indexing_empty";
+    \Drupal::state()->set($key, $state ? \Drupal::time()->getRequestTime() : 0);
+  }
+
 }

src/Plugin/search_api/backend/SearchApiSolrBackend.php

@@ -1467,6 +1467,11 @@ public function getDocuments(IndexInterface $index, array $items, UpdateQuery $u
    * @throws \Drupal\search_api\SearchApiException
    */
   public function deleteItems(IndexInterface $index, array $ids) {
+    /** @var \Drupal\search_api_solr\Entity\Index $index */
+    if ($index->isIndexingEmptyIndex()) {
+      return;
+    }
+
     try {
       $index_id = $this->getTargetedIndexId($index);
       $site_hash = $this->getTargetedSiteHash($index);

src/Utility/SolrCommandHelper.php

@@ -216,12 +216,14 @@ public function indexParallelCommand(array $indexIds = NULL, $threads = 2, $batc
 
     $ids = [];
 
+    /** @var \Drupal\search_api_solr\Entity\Index $index */
     foreach ($indexes as $index) {
       if (!$index->status() || $index->isReadOnly()) {
         continue;
       }
       $tracker = $index->getTrackerInstance();
-      $remaining = $tracker->getTotalItemsCount() - $tracker->getIndexedItemsCount();
+      $indexed = (int) $tracker->getIndexedItemsCount();
+      $remaining = $tracker->getTotalItemsCount() - $indexed;
 
       if (!$remaining) {
         $this->logSuccess($this->t("The index @index is up to date.", ['@index' => $index->label()]));
@@ -258,12 +260,15 @@ public function indexParallelCommand(array $indexIds = NULL, $threads = 2, $batc
         $currentThreads = 1;
       }
 
+      $index->setIndexingEmptyIndex($indexed === 0);
+
       $arguments = [
         '@index' => $index->label(),
         '@threads' => $currentThreads,
         '@batch_size' => $currentBatchSize,
+        '@empty' => $index->isIndexingEmptyIndex() ? $this->t('empty') : $this->t('not empty'),
       ];
-      $this->logSuccess($this->t("Indexing parallel with @threads threads (@batch_size items per batch run) for the index '@index'.", $arguments));
+      $this->logSuccess($this->t("Indexing parallel with @threads threads (@batch_size items per batch run) for the index '@index'. The index is @empty", $arguments));
 
       // Create the batch.
       try {
@@ -298,5 +303,13 @@ public function indexParallelCommand(array $indexIds = NULL, $threads = 2, $batc
     return $shuffled_ids;
   }
 
+  public function resetEmptyIndexState(array $indexIds): void {
+    if ($indexes = $this->loadIndexes($indexIds)) {
+      /** @var \Drupal\search_api_solr\Entity\Index $index */
+      foreach ($indexes as $index) {
+        $index->setIndexingEmptyIndex(FALSE);
+      }
+    }
+  }
 
 }