After upgrading to 4.2.3, I noticed the cscart_seo_redirects table has a ton of entries (double the amount for our products) but nothing in the 'destination' field.
Is it safe to empty this table if I don't need any old URL's to redirect?
Because I'm including the category in the URL, when I change a product's category, the cart inserts the old URL into the seo_redirects table. When the old URL is requested, it is found in this table and CS-Cart uses the product_id in the seo-redirects table to look up the new URL in the seo_names table.
Also, if you change the seo name for a product, it inserts the old seo name into the seo_redirects table (unless you uncheck the checkbox below the seo name).
In my case, since only NEW products are having their categories changed (after import), I TRUNCATE the seo_redirects table after I import products and edit their categories/names/seo name, as none of those URLs are indexed by search engines yet.
You could make a copy of the seo-redirects table (with structure and data), truncate the original and test your results.