[ARROW-14027] [C++][R] Ensure groupers accept scalar inputs (was: Allow me to group_by + summarise() with partitioning fields)

• Type: Bug
• Status: Resolved
• Priority: Blocker
• Resolution: Fixed
• Fix Version/s: 6.0.0
• Component/s: C++, R
• Labels: kernel pull-request-available
• External issue URL: https://github.com/apache/arrow/issues/29625
• Assignee: David Li
• Reporter: Jonathan Keane
• Created: 17/Sep/21 16:44
• Updated: 11/Jan/23 08:37
• Resolved: 29/Sep/21 17:59

Description

If one puts a field that is one of the partitioning variables in group_by() and then summarises, we get a segfault:

library(arrow)
library(dplyr)

temp <- tempfile()

write_dataset(mtcars, path = temp, partitioning = "cyl")

ds <- open_dataset(temp)

# this works just fine
ds %>% 
  group_by(gear) %>% 
  summarise(
    sum(mpg)
  ) %>% 
  collect()

# however this segfaults (regardless of the aggregation, even simply n()) 
#  *** caught segfault ***
# address 0x0, cause 'memory not mapped'
ds %>% 
  group_by(cyl) %>% 
  summarise(
    sum(mpg)
  ) %>% 
  collect()

Issue Links

• links to: GitHub Pull Request #11191