#18387:

catalog:images:resize fails to process all images -> Possible underlying Magento/Framework/DB/Query/Generator issue
- fix getCountAllProductImages select and cover class with unit tests.

app/code/Magento/Catalog/Model/ResourceModel/Product/Image.php

@@ -77,7 +77,13 @@ public function getAllProductImages(): \Generator
      */
     public function getCountAllProductImages(): int
     {
-        $select = $this->getVisibleImagesSelect()->reset('columns')->columns('count(*)');
+        $select = $this->getVisibleImagesSelect()
+            ->reset('columns')
+            ->reset('distinct')
+            ->columns(
+                new \Zend_Db_Expr('count(distinct value)')
+            );
+
         return (int) $this->connection->fetchOne($select);
     }
 

app/code/Magento/Catalog/Test/Unit/Model/ResourceModel/Product/ImageTest.php

@@ -0,0 +1,171 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+declare(strict_types=1);
+
+namespace Magento\Catalog\Test\Unit\Model\ResourceModel\Product;
+
+use Magento\Catalog\Model\ResourceModel\Product\Image;
+use Magento\Framework\DB\Adapter\AdapterInterface;
+use Magento\Framework\DB\Query\Generator;
+use Magento\Framework\DB\Select;
+use Magento\Framework\App\ResourceConnection;
+use Magento\Catalog\Model\ResourceModel\Product\Gallery;
+
+class ImageTest extends \PHPUnit\Framework\TestCase
+{
+    /**
+     * @var AdapterInterface | \PHPUnit_Framework_MockObject_MockObject
+     */
+    protected $connectionMock;
+
+    /**
+     * @var Generator | \PHPUnit_Framework_MockObject_MockObject
+     */
+    protected $generatorMock;
+
+    /**
+     * @var ResourceConnection | \PHPUnit_Framework_MockObject_MockObject
+     */
+    protected $resourceMock;
+
+    /**
+     * @var Image
+     */
+    protected $imageModel;
+
+    /**
+     * @var int
+     */
+    protected $imagesCount = 50;
+
+    /**
+     * @var int
+     */
+    protected $batchSize = 10;
+
+    protected function setUp(): void
+    {
+        $objectManager = new \Magento\Framework\TestFramework\Unit\Helper\ObjectManager($this);
+
+        $this->connectionMock = $this->createMock(AdapterInterface::class);
+
+        $this->resourceMock = $this->createMock(ResourceConnection::class);
+        $this->resourceMock->method('getConnection')->willReturn($this->connectionMock);
+        $this->resourceMock->method('getTableName')->willReturnArgument(0);
+
+        $this->generatorMock = $this->createMock(Generator::class);
+
+        $this->imageModel = $objectManager->getObject(
+            Image::class,
+            [
+                'generator' => $this->generatorMock,
+                'resourceConnection' => $this->resourceMock,
+                'batchSize' => $this->batchSize
+            ]
+        );
+    }
+
+    /**
+     * @return \PHPUnit_Framework_MockObject_MockObject
+     */
+    protected function getVisibleImagesSelectMock(): \PHPUnit_Framework_MockObject_MockObject
+    {
+        $selectMock = $this->getMockBuilder(Select::class)
+            ->disableOriginalConstructor()
+            ->getMock();
+        $selectMock->expects($this->once())
+            ->method('distinct')
+            ->willReturnSelf();
+        $selectMock->expects($this->once())
+            ->method('from')
+            ->with(
+                ['images' => Gallery::GALLERY_TABLE],
+                'value as filepath'
+            )->willReturnSelf();
+        $selectMock->expects($this->once())
+            ->method('where')
+            ->with('disabled = 0')
+            ->willReturnSelf();
+
+        return $selectMock;
+    }
+
+    public function testGetCountAllProductImages(): void
+    {
+        $selectMock = $this->getVisibleImagesSelectMock();
+        $selectMock->expects($this->exactly(2))
+            ->method('reset')
+            ->withConsecutive(
+                ['columns'],
+                ['distinct']
+            )->willReturnSelf();
+        $selectMock->expects($this->once())
+            ->method('columns')
+            ->with(new \Zend_Db_Expr('count(distinct value)'))
+            ->willReturnSelf();
+
+        $this->connectionMock->expects($this->once())
+            ->method('select')
+            ->willReturn($selectMock);
+        $this->connectionMock->expects($this->once())
+            ->method('fetchOne')
+            ->with($selectMock)
+            ->willReturn($this->imagesCount);
+
+        $this->assertSame($this->imagesCount, $this->imageModel->getCountAllProductImages());
+    }
+
+    public function testGetAllProductImages(): void
+    {
+        $getBatchIteratorMock = function ($selectMock, $imagesCount, $batchSize): array {
+            $result = [];
+            $count = $imagesCount / $batchSize;
+            while ($count) {
+                $count--;
+                $result[$count] = $selectMock;
+            }
+
+            return $result;
+        };
+
+        $getAllProductImagesSelectFetchResults = function ($batchSize): array {
+            $result = [];
+            $count = $batchSize;
+            while ($count) {
+                $count--;
+                $result[$count] = $count;
+            }
+
+            return $result;
+        };
+
+        $this->connectionMock->expects($this->once())
+            ->method('select')
+            ->willReturn($this->getVisibleImagesSelectMock());
+
+        $fetchResult = $getAllProductImagesSelectFetchResults($this->batchSize);
+        $this->connectionMock->expects($this->exactly($this->imagesCount / $this->batchSize))
+            ->method('fetchAll')
+            ->willReturn($fetchResult);
+
+        /** @var Select | \PHPUnit_Framework_MockObject_MockObject $selectMock */
+        $selectMock = $this->getMockBuilder(Select::class)
+            ->disableOriginalConstructor()
+            ->getMock();
+
+        $batchIteratorMock = $getBatchIteratorMock($selectMock, $this->imagesCount, $this->batchSize);
+        $this->generatorMock->expects($this->once())
+            ->method('generate')
+            ->with(
+                'value_id',
+                $selectMock,
+                $this->batchSize,
+                \Magento\Framework\DB\Query\BatchIteratorInterface::NON_UNIQUE_FIELD_ITERATOR
+            )->willReturn($batchIteratorMock);
+
+        $this->assertCount($this->imagesCount, $this->imageModel->getAllProductImages());
+    }
+}