使用新缩略图PHP设置Woocommerce产品缩略图

I have created a custom plugin to import and export woocommerce products. I am facing an issue that when i try to import the CSV, the thumbnails of the products got changed and set to the old one which were added to the products earlier.

I have full image URL in the CSV. Here is my import code:

    $product_img = $row[13]; //Product Image
    $res = $wpdb->get_results('select post_id from ' . $wpdb->prefix . 'postmeta where meta_value like "%' . basename($product_img). '%"');
    if(count($res) == 0)
    {
        $res = $wpdb->get_results('select ID as post_id from ' . $wpdb->prefix . 'posts where guid="' . $product_img . '"');
    }
    $thumbnail_id = $res[0]->post_id;

    set_post_thumbnail( $product_id, $thumbnail_id );
    $attach_data = wp_generate_attachment_metadata( $thumbnail_id, $product_img );
    wp_update_attachment_metadata( $thumbnail_id,  $attach_data );

Can anyone tell me where I am wrong and why the thumbnails are updating with the old one. I am trying to find the issue from last 1 day but didn't found it yet.

Thanks in advance.

I found the bug. The first query was returning all the matching result and as picked the first post id so, it returns the first matching post id. The code should be like:

$product_img = $row[13]; //Product Image

    $res = $wpdb->get_results('select ID as post_id from ' . $wpdb->prefix . 'posts where guid="' . $product_img . '"');

$thumbnail_id = $res[0]->post_id;

set_post_thumbnail( $product_id, $thumbnail_id );

This works fine.