memory leaking when reading compressed arrow files

[JesseTsing]

I've posted this when i use python's pandas to read parquet using pyarrow engine, it makes memory leaking problem.
https://issues.apache.org/jira/browse/ARROW-6874?focusedCommentId=17171226&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#comment-17171226

when i use Arrow.jl to read feather, also has the same problem.
code is here:

@showprogress 1 "reading market data" for fp in glob("*.feather","/mnt/Data/market_data/")[1:4]
println(fp)
open(fp) do h
tab = Arrow.Table(read(h))
df = DataFrame(tab)
finalize(tab)
tab = nothing
GC.gc()
end

and mem grows .....
maybe the same problem but different causes....

[quinnj]

In the case of Arrow.jl here, when you do df = DataFrame(tab), the underlying arrow file is not freed, because the columns are re-used from Arrow.Table to DataFrame. If you want to make a copy of the columns, you can do df = DataFrame(tab; copycols=true).