# Error when performing join on Distributed Tables (JuliaDB)

**URL:** <https://discourse.julialang.org/t/error-when-performing-join-on-distributed-tables-juliadb/35800>\
**Category:** New to Julia\
**Tags:** distributed, juliadb\
**Created:** [March 10, 2020, 2:40pm UTC](https://discourse.julialang.org/t/error-when-performing-join-on-distributed-tables-juliadb/35800 "2020-03-10T14:40:53Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![Jakob](https://avatars.discourse-cdn.com/v4/letter/j/71c47a/32.png) [@Jakob](https://discourse.julialang.org/u/Jakob)\
**Post date:** [March 10, 2020, 2:40pm UTC](https://discourse.julialang.org/t/error-when-performing-join-on-distributed-tables-juliadb/35800/1 "2020-03-10T14:40:53Z")

</div>

Hi,

I get the error message shown below when trying to do the following out-of-core join:

```julia
t209_expanded = join(t209, t201_sel, broadcast = :right, how = :left, lkey = :appln_id, rkey = :appln_id)

```

Both input tables are large Distributed Tables, only the right one fits into memory, as required by the manual. I’m not that sure what `broadcast = :right` does, but it was also specified in the documentation on out-of-core joins.

```julia
<strong>MethodError: Cannot `convert` an object of type Nullables.Nullable{Array{Pair{Dagger.OSProc,Int64},1}} to an object of type Array{Pair{Dagger.OSProc,Int64},1}</strong>

<strong>Closest candidates are:
convert(::Type{Array{S,N}}, !Matched::DataValueArray{T,N}) where {S, T, N} at C:\Users\Jakob\.julia\packages\DataValues\N7oeL\src\array\primitives.jl:272
convert(::Type{Array{S,N}}, !Matched::DataValueArray{T,N}, !Matched::Any) where {S, T, N} at C:\Users\Jakob\.julia\packages\DataValues\N7oeL\src\array\primitives.jl:301
convert(::Type{Array{S,N}}, !Matched::PooledArrays.PooledArray{T,R,N,RA} where RA) where {S, T, R, N} at C:\Users\Jakob\.julia\packages\PooledArrays\yiLq3\src\PooledArrays.jl:294
...</strong>

```

Anybody have an idea what’s going wrong?

Thanks!  
Jakob