[Story] Unsupported `polars.Expressions` in cudf-polars

[mroeschke]

In conjunction with developing an agent skill to implement unsupported polars.Expressions, #23078, the following table is the result of an accompanying agent investigation of polars.Expressions that are not supported in our single or multiple partition execution paths. This investigation was done with Polars expressions available as of 1.41.

Fill in the entries in the table with a link to the pull request that implements each expression:

Polars expression (not implemented in cudf-polars)	Single-partition implementation	Multi-partition implementation
append
bitwise_and
bitwise_or
bitwise_xor
bitwise_count_ones		Pointwise - not applicable
bitwise_count_zeros		Pointwise - not applicable
bitwise_leading_ones		Pointwise - not applicable
bitwise_leading_zeros		Pointwise - not applicable
bitwise_trailing_ones		Pointwise - not applicable
bitwise_trailing_zeros		Pointwise - not applicable
cumulative_eval
explode
flatten
map_batches
map_elements		Pointwise - not applicable
sample
shuffle
cut		Pointwise - not applicable
qcut
reshape
rolling_mean
rolling_sum
rolling_max
rolling_min
rolling_median
rolling_quantile
rolling_std
rolling_var
rolling_skew
rolling_kurtosis
rolling_rank
rolling_map
rolling_mean_by
rolling_sum_by
rolling_max_by
rolling_min_by
rolling_median_by
rolling_quantile_by
rolling_std_by
rolling_var_by
rolling_rank_by
agg_groups	Deprecated in 1.35 https://docs.pola.rs/api/python/dev/reference/expressions/api/polars.Expr.agg_groups.html
approx_n_unique	#23211
unique_counts	#23244
arg_max	#23212
arg_min	#23212
arg_sort	#23212
arg_true	#23284
arg_unique	#23212
bottom_k_by	#23213
top_k_by	#23213
max_by	#23224
min_by	#23224
clip	#23162	Pointwise - not applicable
cot	#23191	Pointwise - not applicable
degrees	#23210	Pointwise - not applicable
radians	#23210	Pointwise - not applicable
log1p	#23191	Pointwise - not applicable
sign	#23250	Pointwise - not applicable
cum_count	#23163
diff	#23225
pct_change	#23225
drop_nans	#23165
entropy	#23384
skew	#23353
kurtosis	#23353
extend_constant	#23167
gather_every	#23166
hash	#23313	Pointwise - not applicable
has_nulls	#23168
is_empty	#23170
is_close	#23254	Pointwise - not applicable
hist	#23254
implode	#23226
item	#23226
index_of	#23252
search_sorted	#23252
interpolate
interpolate_by
mode	#23226
product	#23169
peak_max
peak_min
rechunk	#23192	Pointwise - not applicable
reinterpret	#23210	Pointwise - not applicable
to_physical	#23313	Pointwise - not applicable
repeat_by	#23227
replace	#23253	Pointwise - not applicable
replace_strict	#23253	Pointwise - not applicable
reverse	#23164
rle
rle_id
round_sig_figs	#23250	Pointwise - not applicable
truncate	#23244	Pointwise - not applicable
rolling (base time-indexed)
quantile (interpolation="equiprobable")	✅*
rank (method="random")	✅*
over (mapping_strategy ∈ {join,explode})	✅*
cum_sum (reverse=True)	✅* #23164
cum_max (reverse=True)	✅* #23164
cum_min (reverse=True)	✅* #23164
cum_prod (reverse=True)	✅* #23164
fill_null (strategy / limit=…)	✅*
forward_fill	✅
backward_fill	✅
all	✅
any	✅
std	✅
var	✅
median	✅
sort	✅
sort_by	✅
gather	✅
get	✅
filter	✅
where	✅
shift	✅
top_k	✅
bottom_k	✅
value_counts	✅
is_duplicated	✅
is_unique	✅
is_first_distinct	✅
is_last_distinct	✅
str.extract_many		Pointwise - not applicable
str.find_many		Pointwise - not applicable
str.encode		Pointwise - not applicable
str.decode		Pointwise - not applicable
str.escape_regex	#23171	Pointwise - not applicable
str.extract_all		Pointwise - not applicable
str.normalize		Pointwise - not applicable
str.split		Pointwise - not applicable
str.explode
str.to_decimal	#23243	Pointwise - not applicable
str.to_integer	#23194	Pointwise - not applicable
str.to_time		Pointwise - not applicable
str.contains	✅* #23240	Pointwise - not applicable
str.count_matches	✅* #23243	Pointwise - not applicable
str.extract	✅* #23243	Pointwise - not applicable
str.find	✅* #23240	Pointwise - not applicable
str.replace	✅*	Pointwise - not applicable
str.replace_all	✅*	Pointwise - not applicable
str.replace_many	✅*	Pointwise - not applicable
str.slice	✅*	Pointwise - not applicable
str.split_exact	✅*	Pointwise - not applicable
str.strptime	✅*	Pointwise - not applicable
str.to_date	✅*	Pointwise - not applicable
str.to_datetime	✅*	Pointwise - not applicable
str.strip_chars	✅*	Pointwise - not applicable
str.strip_chars_start	✅*	Pointwise - not applicable
str.strip_chars_end	✅*	Pointwise - not applicable
str.head	✅* #23240	Pointwise - not applicable
str.tail	✅* #23240	Pointwise - not applicable
str.zfill	✅* #23193	Pointwise - not applicable
str.concat	✅
str.join	✅
dt.add_business_days		Pointwise - not applicable
dt.is_business_day		Pointwise - not applicable
dt.base_utc_offset		Pointwise - not applicable
dt.convert_time_zone	#23424	Pointwise - not applicable
dt.dst_offset		Pointwise - not applicable
dt.replace_time_zone	#23424	Pointwise - not applicable
dt.century	#23153	Pointwise - not applicable
dt.millennium	#23154	Pointwise - not applicable
dt.combine		Pointwise - not applicable
dt.time		Pointwise - not applicable
dt.date	#23155	Pointwise - not applicable
dt.datetime	Deprecated since 0.20.4 https://docs.pola.rs/api/python/stable/reference/expressions/api/polars.Expr.dt.datetime.html	Pointwise - not applicable
dt.with_time_unit	Deprecated since 0.20.5 https://docs.pola.rs/api/python/stable/reference/expressions/api/polars.Expr.dt.with_time_unit.html	Pointwise - not applicable
dt.days_in_month	#23156	Pointwise - not applicable
dt.quarter	#23157	Pointwise - not applicable
dt.round	#23158	Pointwise - not applicable
dt.offset_by		Pointwise - not applicable
dt.replace		Pointwise - not applicable
dt.total_days	#18171	Pointwise - not applicable
dt.total_hours	#18171	Pointwise - not applicable
dt.total_minutes	#18171	Pointwise - not applicable
dt.total_seconds	#18171	Pointwise - not applicable
dt.total_milliseconds	#18171	Pointwise - not applicable
dt.total_microseconds	#18171	Pointwise - not applicable
dt.total_nanoseconds	#18171	Pointwise - not applicable
dt.truncate (unit > day / non-1<unit>)	✅*	Pointwise - not applicable
list.agg		Pointwise - not applicable
list.all		Pointwise - not applicable
list.any		Pointwise - not applicable
list.eval		Pointwise - not applicable
list.filter		Pointwise - not applicable
list.n_unique		Pointwise - not applicable
list.reverse		Pointwise - not applicable
list.unique		Pointwise - not applicable
list.explode
list.arg_max		Pointwise - not applicable
list.arg_min		Pointwise - not applicable
list.concat		Pointwise - not applicable
list.contains		Pointwise - not applicable
list.count_matches		Pointwise - not applicable
list.diff		Pointwise - not applicable
list.drop_nulls		Pointwise - not applicable
list.first		Pointwise - not applicable
list.gather		Pointwise - not applicable
list.gather_every		Pointwise - not applicable
list.get		Pointwise - not applicable
list.head		Pointwise - not applicable
list.join		Pointwise - not applicable
list.last		Pointwise - not applicable
list.len		Pointwise - not applicable
list.max		Pointwise - not applicable
list.mean		Pointwise - not applicable
list.median		Pointwise - not applicable
list.min		Pointwise - not applicable
list.sample		Pointwise - not applicable
list.set_difference		Pointwise - not applicable
list.set_intersection		Pointwise - not applicable
list.set_symmetric_difference		Pointwise - not applicable
list.set_union		Pointwise - not applicable
list.shift		Pointwise - not applicable
list.slice		Pointwise - not applicable
list.sort		Pointwise - not applicable
list.std		Pointwise - not applicable
list.sum		Pointwise - not applicable
list.tail		Pointwise - not applicable
list.to_struct		Pointwise - not applicable
list.var		Pointwise - not applicable
list.to_array		Pointwise - not applicable
arr.arg_max		Pointwise - not applicable
arr.arg_min		Pointwise - not applicable
arr.contains		Pointwise - not applicable
arr.count_matches		Pointwise - not applicable
arr.explode
arr.first		Pointwise - not applicable
arr.get		Pointwise - not applicable
arr.join		Pointwise - not applicable
arr.last		Pointwise - not applicable
arr.len		Pointwise - not applicable
arr.max		Pointwise - not applicable
arr.mean		Pointwise - not applicable
arr.median		Pointwise - not applicable
arr.min		Pointwise - not applicable
arr.std		Pointwise - not applicable
arr.sum		Pointwise - not applicable
arr.var		Pointwise - not applicable
arr.to_list		Pointwise - not applicable
arr.to_struct		Pointwise - not applicable
arr.agg		Pointwise - not applicable
arr.all		Pointwise - not applicable
arr.any		Pointwise - not applicable
arr.eval		Pointwise - not applicable
arr.head		Pointwise - not applicable
arr.n_unique		Pointwise - not applicable
arr.reverse		Pointwise - not applicable
arr.shift		Pointwise - not applicable
arr.slice		Pointwise - not applicable
arr.sort		Pointwise - not applicable
arr.tail		Pointwise - not applicable
arr.unique		Pointwise - not applicable
struct.with_fields		Pointwise - not applicable
struct.unnest
cat.get_categories
cat.len_bytes		Pointwise - not applicable
cat.len_chars		Pointwise - not applicable
cat.slice		Pointwise - not applicable
cat.starts_with		Pointwise - not applicable
cat.ends_with		Pointwise - not applicable
bin.contains		Pointwise - not applicable
bin.starts_with		Pointwise - not applicable
bin.ends_with		Pointwise - not applicable
bin.get		Pointwise - not applicable
bin.size		Pointwise - not applicable
bin.encode		Pointwise - not applicable
bin.reinterpret		Pointwise - not applicable
bin.decode		Pointwise - not applicable
bin.head		Pointwise - not applicable
bin.tail		Pointwise - not applicable
bin.slice		Pointwise - not applicable
name.map_fields		Pointwise - not applicable
pl.sum_horizontal	#23427	Pointwise - not applicable
pl.min_horizontal	#23427	Pointwise - not applicable
pl.max_horizontal	#23160	Pointwise - not applicable
pl.mean_horizontal	#23427	Pointwise - not applicable
pl.cum_sum_horizontal		Pointwise - not applicable
pl.concat_list		Pointwise - not applicable
pl.fold		Pointwise - not applicable
pl.reduce		Pointwise - not applicable
pl.cum_fold		Pointwise - not applicable
pl.cum_reduce		Pointwise - not applicable
pl.format		Pointwise - not applicable
pl.coalesce	#23159	Pointwise - not applicable
pl.arg_where	#23284
pl.int_range
pl.arange
pl.repeat	#23227
pl.struct	✅

✅* marks expressions that already have a single-partition implementation but reject the specific parameter value(s) noted in parentheses. pl.struct is pointwise expression but is able to have a custom multiple partition implementation