Re 2. Parquet can easily be used with chunked/partitioned files. Then appending is just adding another file/chunk.
The case of 1. really depends on the workload. For embeddings etc selecting column subsets is rare. In order cases, where one has a a bunch of separate features, doing column subsetting might be rather common. But yes, it is far from every case.
The case of 1. really depends on the workload. For embeddings etc selecting column subsets is rare. In order cases, where one has a a bunch of separate features, doing column subsetting might be rather common. But yes, it is far from every case.