Exposing (column) metadata (when reading Parquet files)

[evetion]

Is it possible to expose metadata present in Parquet files read with QuackIO? Ideally it can be attached to objects (e.g. set on a DataFrame via DataAPI metadata) that support metadata.

julia> df = QuackIO.read_parquet(DataFrame, "some.parquet");
julia> metadata(df)
Dict{Any, Any}()  # <-- expect metadata

[evetion]

Something like this would work

# if resulting object supports metadata 
qstr = """select * from parquet_kv_metadata($(kwarg_val_to_db_incomma(fn)))"""
results = DBInterface.execute(DuckDB.DB(), qstr)
for (key, value) in results
	String(key) == "ARROW:schema" && continue  # ignore non-string valued internal metadata
   	metadata!(obj, String(key), value; style=:note)
end

[aplavin]

Agree that would make sense! A PR to add metadata support is definitely welcome :) I'm not that familiar with parquet.