ENGCOM-1250: Use LEFT JOIN When Checking for null Attributes #14356

Author: Stanislav Idolov

app/code/Magento/Eav/Model/Entity/Collection/AbstractCollection.php

@@ -1498,6 +1498,10 @@ protected function _getAttributeConditionSql($attribute, $condition, $joinType =
                 $condition
             );
         } else {
+            if (isset($condition['null'])) {
+                $joinType = 'left';
+            }
+
             $this->_addAttributeJoin($attribute, $joinType);
             if (isset($this->_joinAttributes[$attribute]['condition_alias'])) {
                 $field = $this->_joinAttributes[$attribute]['condition_alias'];

dev/tests/integration/testsuite/Magento/Catalog/Model/ResourceModel/Product/CollectionTest.php

@@ -149,4 +149,20 @@ public function testJoinTable()
 
         self::assertContains($expected, str_replace(PHP_EOL, '', $sql));
     }
+
+    /**
+     * Checks that a collection uses the correct join when filtering by null.
+     *
+     * This actually affects AbstractCollection, but inheritance yada yada.
+     *
+     * @magentoDataFixture Magento/Catalog/Model/ResourceModel/_files/product_simple.php
+     * @magentoDbIsolation enabled
+     */
+    public function testFilterByNull()
+    {
+        $this->collection->addAttributeToFilter([['attribute' => 'special_price', 'null' => true]]);
+        $productCount = $this->collection->count();
+
+        $this->assertEquals(1, $productCount, 'Product with null special_price not found');
+    }
 }