Merge pull request #2542 from magento-performance/MAGETWO-91114

[Performance] [2.3 Forwardport] Performance of Category Products index is slow when you have big number of categories

Author: duhon

app/code/Magento/Catalog/Model/Indexer/Category/Product/AbstractAction.php

@@ -659,25 +659,30 @@ protected function makeTempCategoryTreeIndex()
      */
     protected function fillTempCategoryTreeIndex($temporaryName)
     {
-        // This finds all children (cc2) that descend from a parent (cc) by path.
-        // For example, cc.path may be '1/2', and cc2.path may be '1/2/3/4/5'.
-        $temporarySelect = $this->connection->select()->from(
-            ['cc' => $this->getTable('catalog_category_entity')],
-            ['parent_id' => 'entity_id']
-        )->joinInner(
-            ['cc2' => $this->getTable('catalog_category_entity')],
-            'cc2.path LIKE ' . $this->connection->getConcatSql(
-                [$this->connection->quoteIdentifier('cc.path'), $this->connection->quote('/%')]
-            ),
-            ['child_id' => 'entity_id']
+        $selects = $this->prepareSelectsByRange(
+            $this->connection->select()
+                ->from(
+                    ['c' => $this->getTable('catalog_category_entity')],
+                    ['entity_id', 'path']
+                ),
+            'entity_id'
         );
 
-        $this->connection->query(
-            $temporarySelect->insertFromSelect(
-                $temporaryName,
-                ['parent_id', 'child_id']
-            )
-        );
+        foreach ($selects as $select) {
+            $values = [];
+
+            foreach ($this->connection->fetchAll($select) as $category) {
+                foreach (explode('/', $category['path']) as $parentId) {
+                    if ($parentId !== $category['entity_id']) {
+                        $values[] = [$parentId, $category['entity_id']];
+                    }
+                }
+            }
+
+            if (count($values) > 0) {
+                $this->connection->insertArray($temporaryName, ['parent_id', 'child_id'], $values);
+            }
+        }
     }
 
     /**