# Mmap(io, Vector{Union{Missing,T}}, ...)

**URL:** <https://discourse.julialang.org/t/mmap-io-vector-union-missing-t/8863>\
**Category:** General Usage\
**Tags:** question\
**Created:** [February 6, 2018, 3:19pm UTC](https://discourse.julialang.org/t/mmap-io-vector-union-missing-t/8863 "2018-02-06T15:19:15Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Tamas\_Papp](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/tamas_papp/32/25949_2.png) [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)\
**Post date:** [February 6, 2018, 3:19pm UTC](https://discourse.julialang.org/t/mmap-io-vector-union-missing-t/8863/1 "2018-02-06T15:19:15Z")

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Is there a way I can `mmap` a vector of eltype `Union{Missing, T}` where `isbits(T)`? Clearly `!isbits(Union{Missing, T})`, but I thought this had a compact memory representation now.

OK if it works only in `v0.7`.

As a workaround, can I `mmap` the missingness mask and the data separately, and somehow combine them into the above for the interface?

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**Author:** ![Tamas\_Papp](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/tamas_papp/32/25949_2.png) [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)\
**Post date:** [March 3, 2018, 7:36am UTC](https://discourse.julialang.org/t/mmap-io-vector-union-missing-t/8863/2 "2018-03-03T07:36:12Z")

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Opened an issue:  
[https://github.com/JuliaLang/julia/issues/26309](https://github.com/JuliaLang/julia/issues/26309)