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https://issues.apache.org/jira/browse/ARROW-16503?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Joris Van den Bossche reassigned ARROW-16503:
---------------------------------------------
Assignee: Joris Van den Bossche
> [C++] Can't concatenate extension arrays
> ----------------------------------------
>
> Key: ARROW-16503
> URL: https://issues.apache.org/jira/browse/ARROW-16503
> Project: Apache Arrow
> Issue Type: Improvement
> Components: C++
> Reporter: Dewey Dunnington
> Assignee: Joris Van den Bossche
> Priority: Major
> Labels: good-second-issue
>
> It looks like Arrays with an extension type can't be concatenated. From the R
> bindings:
> {code:R}
> library(arrow, warn.conflicts = FALSE)
> arr <- vctrs_extension_array(1:10)
> concat_arrays(arr, arr)
> #> Error: NotImplemented: concatenation of integer(0)
> #>
> /Users/deweydunnington/Desktop/rscratch/arrow/cpp/src/arrow/array/concatenate.cc:195
> VisitTypeInline(*out_->type, this)
> #>
> /Users/deweydunnington/Desktop/rscratch/arrow/cpp/src/arrow/array/concatenate.cc:590
> ConcatenateImpl(data, pool).Concatenate(&out_data)
> {code}
> This shows up more practically when using the query engine:
> {code:R}
> library(arrow, warn.conflicts = FALSE)
> table <- arrow_table(
> group = rep(c("a", "b"), 5),
> col1 = 1:10,
> col2 = vctrs_extension_array(1:10)
> )
> tf <- tempfile()
> table |> dplyr::group_by(group) |> write_dataset(tf)
> open_dataset(tf) |>
> dplyr::arrange(col1) |>
> dplyr::collect()
> #> Error in `dplyr::collect()`:
> #> ! NotImplemented: concatenation of extension<arrow.r.vctrs>
> #>
> /Users/deweydunnington/Desktop/rscratch/arrow/cpp/src/arrow/array/concatenate.cc:195
> VisitTypeInline(*out_->type, this)
> #>
> /Users/deweydunnington/Desktop/rscratch/arrow/cpp/src/arrow/array/concatenate.cc:590
> ConcatenateImpl(data, pool).Concatenate(&out_data)
> #>
> /Users/deweydunnington/Desktop/rscratch/arrow/cpp/src/arrow/compute/kernels/vector_selection.cc:2025
> Concatenate(values.chunks(), ctx->memory_pool())
> #>
> /Users/deweydunnington/Desktop/rscratch/arrow/cpp/src/arrow/compute/kernels/vector_selection.cc:2084
> TakeCA(*table.column(j), indices, options, ctx)
> #>
> /Users/deweydunnington/Desktop/rscratch/arrow/cpp/src/arrow/compute/exec/sink_node.cc:527
> impl_->DoFinish()
> #>
> /Users/deweydunnington/Desktop/rscratch/arrow/cpp/src/arrow/compute/exec/exec_plan.cc:467
> iterator_.Next()
> #>
> /Users/deweydunnington/Desktop/rscratch/arrow/cpp/src/arrow/record_batch.cc:337
> ReadNext(&batch)
> #>
> /Users/deweydunnington/Desktop/rscratch/arrow/cpp/src/arrow/record_batch.cc:351
> ToRecordBatches()
> {code}
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