Clarify the Parquet FileMetadata value formatting (UTF8 string, JSON-encoded) #6
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Closes #7
The keys and values of Parquet key-value metadata is required to be a string. See the definition in the thrift spec at https://github.com/apache/parquet-format/blob/54e53e5d7794d383529dd30746378f19a12afd58/src/main/thrift/parquet.thrift#L680-L683. In thrift, a
stringis defined as "A text string encoded using UTF-8 encoding".Our current specification of the geo metadata should be fully compliant to this, as it only includes string fields and values, and the whole is JSON encoded, so still a valid UTF8 string.
While removing the TODO item about this, I realized we currently actually don't really mention how the key-values are stored (JSON-encoded string, at least that's what we currently do). So I added a sentence about that to clarify this. This is documenting the current status, although it could maybe also use a broader discussion if we are happy with the JSON encoding (-> opened #7).