This isn't actually about "get file handle", although for, say, a million files that could take a while. This is about having metadata (columns, types, ranges f

This isn't actually about "get file handle", although for, say, a million files that could take a while. This is about having metadata (columns, types, ranges for range partitions, etc) already available to be used in query planning. But these kinds of optimizations only give you dramatic benefits on very specific and relatively small subset of queries rather than on some realistically mixed workload, so to have a fair comparison you'd need to run this realistic workload on a realistic dataset.