marberts opened a new issue, #54682:
URL: https://github.com/apache/arrow/issues/54682
### Describe the bug, including details regarding any error messages,
version, and platform.
`?Schema` says the following about metadata and list columns.
>When converting a data.frame to an Arrow Table or RecordBatch, attributes
from the data.frame are saved alongside tables so that the object can be
reconstructed faithfully in R (e.g. with as.data.frame()). This metadata can be
both at the top-level of the data.frame (e.g. attributes(df)) or at the column
(e.g. attributes(df$col_a)) or for list columns only: element level (e.g.
attributes(df[1, "col_a"])).
Here's an example showing that top-level attributes for a data frame and
attributes for individual columns are preserved, but not for elements of a list
column.
``` r
x <- structure(1:2, comment = "test")
test_df <- list(
x1 = x,
x2 = list(1, x)
) |>
list2DF() |>
structure(comment = "test")
attributes(test_df[1, "x2"]) <- list(comment = "TEST")
str(test_df)
#> 'data.frame': 2 obs. of 2 variables:
#> $ x1: int 1 2
#> ..- attr(*, "comment")= chr "test"
#> $ x2:List of 2
#> ..$ : num 1
#> ..$ : int 1 2
#> .. ..- attr(*, "comment")= chr "test"
#> - attr(*, "comment")= chr "test"
arrow_table <- arrow::as_arrow_table(test_df)
arrow_table$metadata
#> $r
#> $r$attributes
#> $r$attributes$comment
#> [1] "test"
#>
#>
#> $r$columns
#> $r$columns$x1
#> $r$columns$x1$attributes
#> $r$columns$x1$attributes$comment
#> [1] "test"
#>
#>
#> $r$columns$x1$columns
#> NULL
#>
#>
#> $r$columns$x2
#> NULL
str(as.data.frame(arrow_table))
#> 'data.frame': 2 obs. of 2 variables:
#> $ x1: int 1 2
#> ..- attr(*, "comment")= chr "test"
#> $ x2: list<double> [1:2]
#> ..$ : num 1
#> ..$ : num 1 2
#> ..@ ptype: num
#> - attr(*, "comment")= chr "test"
```
<sup>Created on 2026-10-19 with [reprex
v2.1.1](https://reprex.tidyverse.org)</sup>
I ran into this issue when trying to write a data frame with a list column
of named vector with `arrow::write_parquet()` and losing the vector names.
This seems to be related to #42220 and #51695.
```r
> sessionInfo()
R version 4.6.1 (2026-06-24)
Platform: x86_64-pc-linux-gnu
Running under: Ubuntu 24.04.5 LTS
Matrix products: default
BLAS: /usr/lib/x86_64-linux-gnu/blas/libblas.so.3.12.0
LAPACK: /usr/lib/x86_64-linux-gnu/lapack/liblapack.so.3.12.0 LAPACK version
3.12.0
locale:
[1] LC_CTYPE=en_US.UTF-8 LC_NUMERIC=C
LC_TIME=en_US.UTF-8
[4] LC_COLLATE=en_US.UTF-8 LC_MONETARY=en_US.UTF-8
LC_MESSAGES=en_US.UTF-8
[7] LC_PAPER=en_US.UTF-8 LC_NAME=C LC_ADDRESS=C
[10] LC_TELEPHONE=C LC_MEASUREMENT=en_US.UTF-8
LC_IDENTIFICATION=C
time zone: America/Toronto
tzcode source: system (glibc)
attached base packages:
[1] stats graphics grDevices utils datasets methods base
loaded via a namespace (and not attached):
[1] digest_0.6.39 R6_2.6.1 fastmap_1.2.0 xfun_0.57
magrittr_2.0.5
[6] glue_1.8.1 tibble_3.3.1 knitr_1.51 pkgconfig_2.0.3
htmltools_0.5.9
[11] rmarkdown_2.31 lifecycle_1.0.5 ps_1.9.3 cli_3.6.6
processx_3.9.0
[16] callr_3.7.6 vctrs_0.7.3 reprex_2.1.1 withr_3.0.2
compiler_4.6.1
[21] rstudioapi_0.18.0 tools_4.6.1 clipr_0.8.0 pillar_1.11.1
evaluate_1.0.5
[26] yaml_2.3.12 otel_0.2.0 rlang_1.2.0 fs_2.1.0
```
### Component(s)
R
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