Parquetglass: Column Lab

Parquetglass opens a Parquet file and reads only its footer. It verifies the PAR1 magic at both ends of the file, reads the four-byte footer length, and decodes the Thrift compact protocol FileMetaData in pure Swift. Data pages are never decompressed or decoded; every figure on screen comes from the footer. The Summary screen reports format version, writer string, row count, row group count, leaf column count, footer length and offset, data region size, total compressed and uncompressed bytes, the overall compression ratio, and the codecs and encodings used. Footer bytes can be viewed as hex and key-value metadata opened in full. The Schema screen rebuilds the flat element list into a tree. Groups expand, LIST and MAP annotations are labelled, and each leaf shows its physical type, logical or converted type, repetition, field_id, and its max definition and repetition levels. A…