Get all metafields for products

[ReloadSEO]

This has been posted before, but the Shopify support hasn't answered it yet... And it is a good and reasonable question. 

I want to get all the metafields for all the products.

My understanding is that there is no API like:

/admin/products/metafields.json

The only one is like this:

/admin/products/#productid#/metafields.json

Therefore, the only way is to get all the metafields for all the products is to make one API call per product!

It is also impossible to cache the data, because it takes one API call per product just to check if the metafields for that product have been updated!  For large stores, it is handicapping API applications and forcing one call per product, resulting in extremely time-consuming fetches for tiny amounts of data.

Can you please add an API call that works like this?  /admin/products/metafields.json

It would return all the metafields for all the products, 250 at a time.  We can then page through in a reasonable amount of time.

Or, does anyone know some other workaround to get all the product metafields at once?