Product import with more than 100 rows may result in duplicated products

[mimarcel]

This PR fixes issue described in #5780.

Preconditions:

• have latest M2.1 installed
• install demo data (using bin/magento demodata installation options)

Issue:

Product import with more than 100 rows may result in duplicated products.

How to replicate:

• Import a CSV file which has more than 100 rows where rows 100 and 101 belong to the same sku A (different values per store).
• After running the import, you will realise that in importexport_importdata table, sku A will appear in two batches: in the first batch which contains the first 100 rows and in the 2nd batch which contains the next 100 rows (which includes row 101).

Expected:

• Product with sku A is imported only once.

Actual:

• The import does incorrectly identify product with SKU A as new in both batches and, as a consequence, it does duplicate the product.

Solution:

• Product with SKU A should be inserted in the first batch (new product) and it should updated in the 2nd batch (existing product).
• Note that the fix also changes the count of updated products following the idea:

A sku in a batch should be counted as an updated product only if this sku was not inserted or updated in a previous batch.

[NadiyaS]

Hi @mimarcel ,
the issue was already fixed and delivered to develop branch. See commits:
0b05d4d,
a4c7261,
d48f1e2,
0919256,
7796729.
I will close your PR.
Thank you for your contribution.