parquet-to-open-table-format

Decides when a directory of Parquet files has stopped being enough to hold a dataset, by naming what that layer cannot do, from correcting a row to surviving two writers, keeping a column somebody added, or giving a reader the same answer twice. Use when files are being rewritten to fix rows, when more than one process writes the same dataset, when a column was added and the older files do not have it, or when a reader needs the data as it stood at a point in time.