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Check field nullability for custom extension types (#69)
For custom extension types (currently automatically supported for `Char`
and `Symbol` types), we were failing to take into account whether the
field was nullable or not; this led to the case where a column might be
`['a', missing]`, but when deserializing, the column type was just
`Char` instead of `Union{Char, Missing}`. The fix is to enhance the
`ArrowTypes.extensiontype` function to also take the `field` argument
and check the nullability before returning.
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quinnj committed Nov 19, 2020
1 parent 73e08db commit c33a8186d1f5f3972483c87ab9307afb58d936db
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Showing 2 changed files with 4 additions and 3 deletions.
@@ -131,11 +131,12 @@ const ARROW_TO_JULIA_TYPE_MAPPING = Dict{String, Tuple{Type, Type}}(
"JuliaLang.Symbol" => (Symbol, String),

function extensiontype(meta)
function extensiontype(f, meta)
if haskey(meta, "ARROW:extension:name")
typename = meta["ARROW:extension:name"]
if haskey(ARROW_TO_JULIA_TYPE_MAPPING, typename)
return ARROW_TO_JULIA_TYPE_MAPPING[typename][1]
return f.nullable ? Union{T, Missing} : T
@warn "unsupported ARROW:extension:name type: \"$typename\""
@@ -43,7 +43,7 @@ function juliaeltype(f::Meta.Field, meta::Dict{String, String}, convert::Bool)
TT = juliaeltype(f, convert)
!convert && return TT
T = finaljuliatype(TT)
TTT = ArrowTypes.extensiontype(meta)
TTT = ArrowTypes.extensiontype(f, meta)
return something(TTT, T)

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