MC-25235: Tier Prices error on product update

Author: yelahin-serhiy

app/code/Magento/Catalog/Model/Product/Attribute/Backend/TierPrice/UpdateHandler.php

@@ -96,12 +96,7 @@ public function execute($entity, $arguments = [])
             $productId = (int)$entity->getData($identifierField);
 
             // prepare original data to compare
-            $origPrices = [];
-            $originalId = $entity->getOrigData($identifierField);
-            if (empty($originalId) || $entity->getData($identifierField) == $originalId) {
-                $origPrices = $entity->getOrigData($attribute->getName());
-            }
-
+            $origPrices = $entity->getOrigData($attribute->getName());
             $old = $this->prepareOldTierPriceToCompare($origPrices);
             // prepare data for save
             $new = $this->prepareNewDataForSave($priceRows, $isGlobal);

app/code/Magento/Catalog/Test/Unit/Model/Attribute/Backend/TierPrice/UpdateHandlerTest.php

@@ -108,6 +108,7 @@ public function testExecute(): void
         ];
         $linkField = 'entity_id';
         $productId = 10;
+        $originalProductId = 11;
 
         /** @var \PHPUnit_Framework_MockObject_MockObject $product */
         $product = $this->getMockBuilder(\Magento\Catalog\Api\Data\ProductInterface::class)
@@ -124,7 +125,7 @@ public function testExecute(): void
             ->willReturnMap(
                 [
                     ['tier_price', $originalTierPrices],
-                    ['entity_id', $productId]
+                    ['entity_id', $originalProductId]
                 ]
             );
         $product->expects($this->atLeastOnce())->method('getStoreId')->willReturn(0);