jonkeane commented on a change in pull request #11183:
URL: https://github.com/apache/arrow/pull/11183#discussion_r712522575
##########
File path: r/R/query-engine.R
##########
@@ -20,11 +20,36 @@ do_exec_plan <- function(.data) {
final_node <- plan$Build(.data)
tab <- plan$Run(final_node)
+ # If arrange() created $temp_columns, make sure to omit them from the result
+ # We can't currently handle this in the ExecPlan itself because sorting
+ # happens in the end (SinkNode) so nothing comes after it.
if (length(final_node$sort$temp_columns) > 0) {
- # If arrange() created $temp_columns, make sure to omit them from the
result
tab <- tab[, setdiff(names(tab), final_node$sort$temp_columns), drop =
FALSE]
}
+ if (ncol(tab)) {
+ # Apply any column metadata from the original schema, where appropriate
+ original_schema <- source_data(.data)$schema
+ # TODO: do we care about other (non-R) metadata preservation?
Review comment:
Hmm, Arrow to R conversion losing the metadata sounds like what I
expected. TBH I _am_ a little surprised that the following happens silently,
since the `tab` below _does_ have the pandas metadata there. Though that's been
in Arrow for a while and if no one has complained, I guess it's not that
important.
```
> tab <- read_parquet(system.file("v0.7.1.parquet", package = "arrow"),
as_data_frame = FALSE)
>
> dplyr::select(tab, carat)$metadata
NULL
```
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