SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry 'commerce_product-2462' for key 1

No. as i told you the product sku's used for this import process are uinique.

And even so shouldn't update the products with the same sku??

(Using update existing products on commerce product processor settings)

No i dont have any existing products and commerce_product database table is empty. Also using the latest dev version

I have made a test importer using rfay feed example (http://d7.randyfay.com/books/feed).

Here is the export.

$feeds_importer = new stdClass;
$feeds_importer->disabled = FALSE; /* Edit this to true to make a default feeds_importer disabled initially */
$feeds_importer->api_version = 1;
$feeds_importer->id = 'test_importer';
$feeds_importer->config = array(
  'name' => 'Test Importer',
  'description' => 'Test import',
  'fetcher' => array(
    'plugin_key' => 'FeedsHTTPFetcher',
    'config' => array(
      'auto_detect_feeds' => FALSE,
      'use_pubsubhubbub' => FALSE,
      'designated_hub' => '',
    ),
  ),
  'parser' => array(
    'plugin_key' => 'FeedsCSVParser',
    'config' => array(
      'delimiter' => ',',
      'no_headers' => 0,
    ),
  ),
  'processor' => array(
    'plugin_key' => 'FeedsCommerceProductProcessor',
    'config' => array(
      'product_type' => 'products_with_voucher',
      'author' => '1',
      'tax_rate' => 'greek_tax_rate',
      'mappings' => array(
        0 => array(
          'source' => 'SKU',
          'target' => 'sku',
          'unique' => 1,
        ),
        1 => array(
          'source' => 'Title',
          'target' => 'title',
          'unique' => FALSE,
        ),
        2 => array(
          'source' => 'Price',
          'target' => 'commerce_price:amount',
          'unique' => FALSE,
        ),
        3 => array(
          'source' => 'Image',
          'target' => 'field_gift_photos',
          'unique' => FALSE,
        ),
        4 => array(
          'source' => 'Description',
          'target' => 'field_description',
          'unique' => FALSE,
        ),
      ),
      'update_existing' => '2',
      'input_format' => 'plain_text',
    ),
  ),
  'content_type' => '',
  'update' => 0,
  'import_period' => '-1',
  'expire_period' => 3600,
  'import_on_create' => 1,
  'process_in_background' => 0,
);

And here is a part of the log data in the test importer.

SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry 'commerce_product-2564' for key 1
Original item
array (
  'sku' => '0471176494',
  'title' => 'The Computer Consultant\'s Guide: Real-Life Strategies for Building a Successful Consulting Career',
  'price' => '5000',
  'image' => 'http://ecx.images-amazon.com/images/I/51nnXx9tUCL.jpg',
  'description' => 'THE COMPUTER CONSULTANT\'S GUIDEIf you\'re ideas od marketing skills * Find and manage the highest paying clients * Set fees and bid on the big jobs * Handle important tax and accounting issues * Work through brokers with confidence',
  'stock' => '100',
)
Entity
stdClass::__set_state(array(
   'type' => 'products_with_voucher',
   'product_id' => '2564',
   'uid' => '1',
   'status' => 1,
   'created' => 1326964794,
   'changed' => 1326964794,
   'feeds_item' => 
  stdClass::__set_state(array(
     'entity_id' => '2564',
     'entity_type' => 'commerce_product',
     'id' => 'test_importer',
     'feed_nid' => 0,
     'imported' => 1326964794,
     'hash' => '422315c389ea35d07a6fcb37aa50e00b',
     'url' => '',
     'guid' => '',
  )),
   'sku' => '0471176494',
   'title' => 'The Computer Consultant\'s Guide: Real-Life Strategies for Building a Successful Consulting Career',
   'commerce_price' => 
  array (
    'und' => 
    array (
      0 => 
      array (
        'currency_code' => 'EUR',
        'amount' => '5000',
        'data' => 
        array (
          'include_tax' => 'greek_tax_rate',
          'components' => 
          array (
          ),
        ),
      ),
    ),
  ),
   'field_gift_photos' => 
  array (
    'und' => 
    array (
      0 => 
      array (
        'fid' => '2656',
        'uri' => 'public://Product Images/51nnXx9tUCL.jpg',
        'filename' => '51nnXx9tUCL.jpg',
        'filemime' => 'image/jpeg',
        'uid' => '1',
        'status' => 1,
        'timestamp' => 1326964794,
        'filesize' => 48724,
        'type' => 'image',
        'display' => 1,
        'width' => 328,
        'height' => 500,
      ),
    ),
  ),
   'field_description' => 
  array (
    'und' => 
    array (
      0 => 
      array (
        'value' => 'THE COMPUTER CONSULTANT\'S GUIDEIf you\'re serious al business and marketing skills * Find and manage the highest paying clients * Set fees and bid on the big jobs * Handle important tax and accounting issues * Work through brokers with confidence',
        'format' => 'plain_text',
      ),
    ),

Ok here is another interesting thing i found.

If i choose the default product type that comes with drupal commerce for the imported products, the process completes successfully.

In the mapping settings i have selected the default fields only ( Product Sku , Title, Price), no custom fields.

So when i change back to my custom product type with the same default fields i get the error message above.

Both of tests with no existing products in any product type

Any idea why this is happening?

Also i can add any product of any product type via the product administration form without any errors

Finally i found what the problem is.

The problem lies in Rules. I had created two custom rules that react on "after saving a product" and "after updating a product" and calculated some of my product fields which are read-only.

After disabling them, the import process completed successfully. So we can't have rules applied "on saving new products " events during the import process i guess?!

Also during the non-successfull import processes download to my server hunderds of images (each of them had 5 duplicates).

After i removed them from the public file and tried to import one product with the same image source i got a similar error for duplicate files.

As i suspect the file_managed table must be emptied in order to avoid this collision??

Yes this is a new site in test mode.. so i think it's safe in this mode..

As far as concerning these rules, could these be fixed..?

Those rules work just fine when i add a product via the product administration form.

Nevertheless, i maybe open another issue if i dont figure this out. Thanks for your posts.