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https://issues.apache.org/jira/browse/ARROW-15833?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Dragoș Moldovan-Grünfeld closed ARROW-15833.
--------------------------------------------
Resolution: Duplicate
> [C++] Support casting from duration to string/utf8
> --------------------------------------------------
>
> Key: ARROW-15833
> URL: https://issues.apache.org/jira/browse/ARROW-15833
> Project: Apache Arrow
> Issue Type: Improvement
> Components: C++, R
> Affects Versions: 7.0.0
> Reporter: Dragoș Moldovan-Grünfeld
> Priority: Major
>
> Cast from {{duration[s]}} to {{utf8}} is not supported. This surfaced in R as
> an error when trying to write to CSV.
> {code:r}
> arrow::write_csv_arrow(data.frame(time = as.difftime(1, units="secs")),
> "test.csv")
> #> Error: NotImplemented: Unsupported cast from duration[s] to utf8 using
> function cast_string
> {code}
>
> {code:r}
> library(arrow, warn.conflicts = FALSE)
> #> See arrow_info() for available features
> c <- Array$create(as.difftime(32, units = "secs"))
> c
> #> Array
> #> <duration[s]>
> #> [
> #> 32
> #> ]
> c$cast(string())
> #> Error: NotImplemented: Unsupported cast from duration[s] to utf8 using
> function cast_string
> #> /Users/dragos/Documents/arrow/cpp/src/arrow/compute/function.cc:231
> DispatchBest(&inputs)
> {code}
> I guess the desired output would be to cast to "current" units even if we
> lose the metadata. Casting to {{int64()}} works (in a similar, lossy way).
> {code:r}
> c$cast(int64())$cast(string())
> #> Array
> #> <string>
> #> [
> #> "32"
> #> ]
> c$cast(duration(unit = "ms"))$cast(int64())$cast(string())
> #> Array
> #> <string>
> #> [
> #> "32000"
> #> ]
> {code}
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