Is it possible to export all metric data for a given metric type?

I have several million metrics of a type “Placed Order” which I have sent via API into Klavio.

This metric is of the form:

{'$value': 279.72, '$event_id': '1615469952', '$attribution': {}, '$extra': {'Items': m{'SKU': 'H05*TL005-END/C', '$value': '259.00', 'vendor': 'H05', 'name': 'GEN E Table', 'price': '259.00', 'qty': '1', 'ext_price': '259.00', 'sys_price': '249.00', 'vend_stk_no': 'TL005-END/C', 'desc': 'GEN ETable'}]}, 'store_no': '92', 'tax_perc': '8.000', 'inv_no': '543570', 'subtotal': '259.00', 'id': '838*543570'}

I wanted to use the “metric export api” to run a query based on the the Items of this metric. However because the Items attribute is a nested field (under $extra→ Items), this is not possible

Further more the metrics api only allows 100 metrics to be given at a time, meaning downloading the entire collection of metrics through the api could take days.

Is there some mechanism to download or dump all this data. Even a solution that sends it to a third party that has more aggressive analytics for nested fields is an option.

Alternatively is is possible to do a one time modification of a metric’s structure to un nest a field?