[jira] [Commented] (ARROW-7028) Dates in R are different when saved and loaded with parquet

["Uwe Korn (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ARROW-7028?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16962860#comment-16962860 ] 

Uwe Korn commented on ARROW-7028:
---------------------------------

cc [~npr] This is the issue I talked about on Zulip yesterday. This time with an argument why we should ensure better reconstruction.

> Dates in R are different when saved and loaded with parquet
> -----------------------------------------------------------
>
>                 Key: ARROW-7028
>                 URL: https://issues.apache.org/jira/browse/ARROW-7028
>             Project: Apache Arrow
>          Issue Type: Bug
>          Components: R
>    Affects Versions: 0.15.0
>            Reporter: Sascha
>            Priority: Major
>
> When saving R-dataframes with parquet and loading them again, the internal representation of Dates changes, leading e.g. to errors when comparing them in dplyr::if_else.
> {code}
> library(dplyr)
> #> 
> #> Attaching package: 'dplyr'
> #> The following objects are masked from 'package:stats':
> #> 
> #> filter, lag
> #> The following objects are masked from 'package:base':
> #> 
> #> intersect, setdiff, setequal, union
> tmp = tempdir()
> dat = tibble(tag = as.Date("2018-01-01"))
> dat2 = tibble(tag2 = as.Date("2019-01-01"))
> arrow::write_parquet(dat, file.path(tmp, "dat.parquet"))
> dat = arrow::read_parquet(file.path(tmp, "dat.parquet"))
> typeof(dat$tag)
> #> [1] "integer"
> typeof(dat2$tag2)
> #> [1] "double"
> bind_cols(dat, dat2) %>%
>  mutate(comparison = if_else(TRUE, tag, tag2))
> #> `false` must be a `Date` object, not a `Date` object
> {code}
> Created on 2019-10-30 by the [reprex package](https://reprex.tidyverse.org) (v0.3.0)



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