Andy Teucher created ARROW-16007:
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Summary: [R] binding for grepl has different behaviour with NA
compared to R base grepl
Key: ARROW-16007
URL: https://issues.apache.org/jira/browse/ARROW-16007
Project: Apache Arrow
Issue Type: Improvement
Affects Versions: 7.0.0
Reporter: Andy Teucher
The arrow binding to {{grepl}} behaves slightly differently than the base R
{{{}grepl{}}}, in that it returns {{NA}} for {{NA}} inputs, whereas base
{{grepl}} returns {{FALSE }}with{{ NA }}inputs. arrow's implementention is
consistent with {{{}stringr::str_detect(){}}}, and both {{str_detect()}} and
{{grepl()}} are bound to {{match_substring_regex}} and {{match_substring}} in
arrow.
I don't know if this is something you would want to change so that the
{{grepl}} behaviour aligns with base {{{}grepl{}}}, or simply document this
difference?
Reprex:
{code:r}
library(arrow, warn.conflicts = FALSE, quietly = TRUE)
library(dplyr, warn.conflicts = FALSE, quietly = TRUE)
library(stringr, quietly = TRUE)
alpha_df <- data.frame(alpha = c("alpha", "bet", NA_character_))
alpha_dataset <- InMemoryDataset$create(alpha_df)
mutate(alpha_df,
grepl_is_a = grepl("a", alpha),
stringr_is_a = str_detect(alpha, "a"))
#> alpha grepl_is_a stringr_is_a
#> 1 alpha TRUE TRUE
#> 2 bet FALSE FALSE
#> 3 <NA> FALSE NA
mutate(alpha_dataset,
grepl_is_a = grepl("a", alpha),
stringr_is_a = str_detect(alpha, "a")) |>
collect()
#> alpha grepl_is_a stringr_is_a
#> 1 alpha TRUE TRUE
#> 2 bet FALSE FALSE
#> 3 <NA> NA NA
# base R grepl returns FALSE for NA
grepl("a", alpha_df$alpha) # bound to arrow_match_substring_regex
#> [1] TRUE FALSE FALSE
grepl("a", alpha_df$alpha, fixed = TRUE) # bound to arrow_match_substring
#> [1] TRUE FALSE FALSE
# stringr::str_dectect returns NA for NA
str_detect(alpha_df$alpha, "a")
#> [1] TRUE FALSE NA
alpha_array <- Array$create(alpha_df$alpha)
# arrow functions return null for null (NA)
call_function("match_substring_regex", alpha_array, options = list(pattern =
"a"))
#> Array
#> <bool>
#> [
#> true,
#> false,
#> null
#> ]
call_function("match_substring", alpha_array, options = list(pattern = "a"))
#> Array
#> <bool>
#> [
#> true,
#> false,
#> null
#> ]
{code}
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