polars_core/frame/group_by/
position.rs

1use std::mem::ManuallyDrop;
2use std::ops::{Deref, DerefMut};
3
4use arrow::offset::OffsetsBuffer;
5use polars_utils::idx_vec::IdxVec;
6use rayon::iter::plumbing::UnindexedConsumer;
7use rayon::prelude::*;
8
9use crate::POOL;
10use crate::prelude::*;
11use crate::utils::{NoNull, flatten, slice_slice};
12
13/// Indexes of the groups, the first index is stored separately.
14/// this make sorting fast.
15#[derive(Debug, Clone, PartialEq, Eq, Default)]
16pub struct GroupsIdx {
17    pub(crate) sorted: bool,
18    first: Vec<IdxSize>,
19    all: Vec<IdxVec>,
20}
21
22pub type IdxItem = (IdxSize, IdxVec);
23pub type BorrowIdxItem<'a> = (IdxSize, &'a IdxVec);
24
25impl Drop for GroupsIdx {
26    fn drop(&mut self) {
27        let v = std::mem::take(&mut self.all);
28        // ~65k took approximately 1ms on local machine, so from that point we drop on other thread
29        // to stop query from being blocked
30        #[cfg(not(target_family = "wasm"))]
31        if v.len() > 1 << 16 {
32            std::thread::spawn(move || drop(v));
33        } else {
34            drop(v);
35        }
36
37        #[cfg(target_family = "wasm")]
38        drop(v);
39    }
40}
41
42impl From<Vec<IdxItem>> for GroupsIdx {
43    fn from(v: Vec<IdxItem>) -> Self {
44        v.into_iter().collect()
45    }
46}
47
48impl From<Vec<Vec<IdxItem>>> for GroupsIdx {
49    fn from(v: Vec<Vec<IdxItem>>) -> Self {
50        // single threaded flatten: 10% faster than `iter().flatten().collect()
51        // this is the multi-threaded impl of that
52        let (cap, offsets) = flatten::cap_and_offsets(&v);
53        let mut first = Vec::with_capacity(cap);
54        let first_ptr = first.as_ptr() as usize;
55        let mut all = Vec::with_capacity(cap);
56        let all_ptr = all.as_ptr() as usize;
57
58        POOL.install(|| {
59            v.into_par_iter()
60                .zip(offsets)
61                .for_each(|(mut inner, offset)| {
62                    unsafe {
63                        let first = (first_ptr as *const IdxSize as *mut IdxSize).add(offset);
64                        let all = (all_ptr as *const IdxVec as *mut IdxVec).add(offset);
65
66                        let inner_ptr = inner.as_mut_ptr();
67                        for i in 0..inner.len() {
68                            let (first_val, vals) = std::ptr::read(inner_ptr.add(i));
69                            std::ptr::write(first.add(i), first_val);
70                            std::ptr::write(all.add(i), vals);
71                        }
72                        // set len to 0 so that the contents will not get dropped
73                        // they are moved to `first` and `all`
74                        inner.set_len(0);
75                    }
76                });
77        });
78        unsafe {
79            all.set_len(cap);
80            first.set_len(cap);
81        }
82        GroupsIdx {
83            sorted: false,
84            first,
85            all,
86        }
87    }
88}
89
90impl GroupsIdx {
91    pub fn new(first: Vec<IdxSize>, all: Vec<IdxVec>, sorted: bool) -> Self {
92        Self { sorted, first, all }
93    }
94
95    pub fn sort(&mut self) {
96        if self.sorted {
97            return;
98        }
99        let mut idx = 0;
100        let first = std::mem::take(&mut self.first);
101        // store index and values so that we can sort those
102        let mut idx_vals = first
103            .into_iter()
104            .map(|v| {
105                let out = [idx, v];
106                idx += 1;
107                out
108            })
109            .collect_trusted::<Vec<_>>();
110        idx_vals.sort_unstable_by_key(|v| v[1]);
111
112        let take_first = || idx_vals.iter().map(|v| v[1]).collect_trusted::<Vec<_>>();
113        let take_all = || {
114            idx_vals
115                .iter()
116                .map(|v| unsafe {
117                    let idx = v[0] as usize;
118                    std::mem::take(self.all.get_unchecked_mut(idx))
119                })
120                .collect_trusted::<Vec<_>>()
121        };
122        let (first, all) = POOL.install(|| rayon::join(take_first, take_all));
123        self.first = first;
124        self.all = all;
125        self.sorted = true
126    }
127    pub fn is_sorted_flag(&self) -> bool {
128        self.sorted
129    }
130
131    pub fn iter(
132        &self,
133    ) -> std::iter::Zip<
134        std::iter::Copied<std::slice::Iter<'_, IdxSize>>,
135        std::slice::Iter<'_, IdxVec>,
136    > {
137        self.into_iter()
138    }
139
140    pub fn all(&self) -> &[IdxVec] {
141        &self.all
142    }
143
144    pub fn first(&self) -> &[IdxSize] {
145        &self.first
146    }
147
148    pub fn first_mut(&mut self) -> &mut Vec<IdxSize> {
149        &mut self.first
150    }
151
152    pub(crate) fn len(&self) -> usize {
153        self.first.len()
154    }
155
156    pub(crate) unsafe fn get_unchecked(&self, index: usize) -> BorrowIdxItem<'_> {
157        let first = *self.first.get_unchecked(index);
158        let all = self.all.get_unchecked(index);
159        (first, all)
160    }
161
162    // Create an 'empty group', containing 1 group of length 0
163    pub fn new_empty() -> Self {
164        Self {
165            sorted: false,
166            first: vec![0],
167            all: vec![vec![].into()],
168        }
169    }
170}
171
172impl FromIterator<IdxItem> for GroupsIdx {
173    fn from_iter<T: IntoIterator<Item = IdxItem>>(iter: T) -> Self {
174        let (first, all) = iter.into_iter().unzip();
175        GroupsIdx {
176            sorted: false,
177            first,
178            all,
179        }
180    }
181}
182
183impl<'a> IntoIterator for &'a GroupsIdx {
184    type Item = BorrowIdxItem<'a>;
185    type IntoIter = std::iter::Zip<
186        std::iter::Copied<std::slice::Iter<'a, IdxSize>>,
187        std::slice::Iter<'a, IdxVec>,
188    >;
189
190    fn into_iter(self) -> Self::IntoIter {
191        self.first.iter().copied().zip(self.all.iter())
192    }
193}
194
195impl IntoIterator for GroupsIdx {
196    type Item = IdxItem;
197    type IntoIter = std::iter::Zip<std::vec::IntoIter<IdxSize>, std::vec::IntoIter<IdxVec>>;
198
199    fn into_iter(mut self) -> Self::IntoIter {
200        let first = std::mem::take(&mut self.first);
201        let all = std::mem::take(&mut self.all);
202        first.into_iter().zip(all)
203    }
204}
205
206impl FromParallelIterator<IdxItem> for GroupsIdx {
207    fn from_par_iter<I>(par_iter: I) -> Self
208    where
209        I: IntoParallelIterator<Item = IdxItem>,
210    {
211        let (first, all) = par_iter.into_par_iter().unzip();
212        GroupsIdx {
213            sorted: false,
214            first,
215            all,
216        }
217    }
218}
219
220impl<'a> IntoParallelIterator for &'a GroupsIdx {
221    type Iter = rayon::iter::Zip<
222        rayon::iter::Copied<rayon::slice::Iter<'a, IdxSize>>,
223        rayon::slice::Iter<'a, IdxVec>,
224    >;
225    type Item = BorrowIdxItem<'a>;
226
227    fn into_par_iter(self) -> Self::Iter {
228        self.first.par_iter().copied().zip(self.all.par_iter())
229    }
230}
231
232impl IntoParallelIterator for GroupsIdx {
233    type Iter = rayon::iter::Zip<rayon::vec::IntoIter<IdxSize>, rayon::vec::IntoIter<IdxVec>>;
234    type Item = IdxItem;
235
236    fn into_par_iter(mut self) -> Self::Iter {
237        let first = std::mem::take(&mut self.first);
238        let all = std::mem::take(&mut self.all);
239        first.into_par_iter().zip(all.into_par_iter())
240    }
241}
242
243/// Every group is indicated by an array where the
244///  - first value is an index to the start of the group
245///  - second value is the length of the group
246///
247/// Only used when group values are stored together
248///
249/// This type should have the invariant that it is always sorted in ascending order.
250pub type GroupsSlice = Vec<[IdxSize; 2]>;
251
252#[derive(Debug, Clone, PartialEq, Eq)]
253pub enum GroupsType {
254    Idx(GroupsIdx),
255    /// Slice is always sorted in ascending order.
256    Slice {
257        // the groups slices
258        groups: GroupsSlice,
259        // indicates if we do a rolling group_by
260        rolling: bool,
261    },
262}
263
264impl Default for GroupsType {
265    fn default() -> Self {
266        GroupsType::Idx(GroupsIdx::default())
267    }
268}
269
270impl GroupsType {
271    pub fn into_idx(self) -> GroupsIdx {
272        match self {
273            GroupsType::Idx(groups) => groups,
274            GroupsType::Slice { groups, .. } => {
275                polars_warn!(
276                    "Had to reallocate groups, missed an optimization opportunity. Please open an issue."
277                );
278                groups
279                    .iter()
280                    .map(|&[first, len]| (first, (first..first + len).collect::<IdxVec>()))
281                    .collect()
282            },
283        }
284    }
285
286    pub(crate) fn prepare_list_agg(
287        &self,
288        total_len: usize,
289    ) -> (Option<IdxCa>, OffsetsBuffer<i64>, bool) {
290        let mut can_fast_explode = true;
291        match self {
292            GroupsType::Idx(groups) => {
293                let mut list_offset = Vec::with_capacity(self.len() + 1);
294                let mut gather_offsets = Vec::with_capacity(total_len);
295
296                let mut len_so_far = 0i64;
297                list_offset.push(len_so_far);
298
299                for idx in groups {
300                    let idx = idx.1;
301                    gather_offsets.extend_from_slice(idx);
302                    len_so_far += idx.len() as i64;
303                    list_offset.push(len_so_far);
304                    can_fast_explode &= !idx.is_empty();
305                }
306                unsafe {
307                    (
308                        Some(IdxCa::from_vec(PlSmallStr::EMPTY, gather_offsets)),
309                        OffsetsBuffer::new_unchecked(list_offset.into()),
310                        can_fast_explode,
311                    )
312                }
313            },
314            GroupsType::Slice { groups, .. } => {
315                let mut list_offset = Vec::with_capacity(self.len() + 1);
316                let mut gather_offsets = Vec::with_capacity(total_len);
317                let mut len_so_far = 0i64;
318                list_offset.push(len_so_far);
319
320                for g in groups {
321                    let len = g[1];
322                    let offset = g[0];
323                    gather_offsets.extend(offset..offset + len);
324
325                    len_so_far += len as i64;
326                    list_offset.push(len_so_far);
327                    can_fast_explode &= len > 0;
328                }
329
330                unsafe {
331                    (
332                        Some(IdxCa::from_vec(PlSmallStr::EMPTY, gather_offsets)),
333                        OffsetsBuffer::new_unchecked(list_offset.into()),
334                        can_fast_explode,
335                    )
336                }
337            },
338        }
339    }
340
341    pub fn iter(&self) -> GroupsTypeIter<'_> {
342        GroupsTypeIter::new(self)
343    }
344
345    pub fn sort(&mut self) {
346        match self {
347            GroupsType::Idx(groups) => {
348                if !groups.is_sorted_flag() {
349                    groups.sort()
350                }
351            },
352            GroupsType::Slice { .. } => {
353                // invariant of the type
354            },
355        }
356    }
357
358    pub(crate) fn is_sorted_flag(&self) -> bool {
359        match self {
360            GroupsType::Idx(groups) => groups.is_sorted_flag(),
361            GroupsType::Slice { .. } => true,
362        }
363    }
364
365    pub fn take_group_firsts(self) -> Vec<IdxSize> {
366        match self {
367            GroupsType::Idx(mut groups) => std::mem::take(&mut groups.first),
368            GroupsType::Slice { groups, .. } => {
369                groups.into_iter().map(|[first, _len]| first).collect()
370            },
371        }
372    }
373
374    /// # Safety
375    /// This will not do any bounds checks. The caller must ensure
376    /// all groups have members.
377    pub unsafe fn take_group_lasts(self) -> Vec<IdxSize> {
378        match self {
379            GroupsType::Idx(groups) => groups
380                .all
381                .iter()
382                .map(|idx| *idx.get_unchecked(idx.len() - 1))
383                .collect(),
384            GroupsType::Slice { groups, .. } => groups
385                .into_iter()
386                .map(|[first, len]| first + len - 1)
387                .collect(),
388        }
389    }
390
391    pub fn par_iter(&self) -> GroupsTypeParIter<'_> {
392        GroupsTypeParIter::new(self)
393    }
394
395    /// Get a reference to the `GroupsIdx`.
396    ///
397    /// # Panic
398    ///
399    /// panics if the groups are a slice.
400    pub fn unwrap_idx(&self) -> &GroupsIdx {
401        match self {
402            GroupsType::Idx(groups) => groups,
403            GroupsType::Slice { .. } => panic!("groups are slices not index"),
404        }
405    }
406
407    /// Get a reference to the `GroupsSlice`.
408    ///
409    /// # Panic
410    ///
411    /// panics if the groups are an idx.
412    pub fn unwrap_slice(&self) -> &GroupsSlice {
413        match self {
414            GroupsType::Slice { groups, .. } => groups,
415            GroupsType::Idx(_) => panic!("groups are index not slices"),
416        }
417    }
418
419    pub fn get(&self, index: usize) -> GroupsIndicator<'_> {
420        match self {
421            GroupsType::Idx(groups) => {
422                let first = groups.first[index];
423                let all = &groups.all[index];
424                GroupsIndicator::Idx((first, all))
425            },
426            GroupsType::Slice { groups, .. } => GroupsIndicator::Slice(groups[index]),
427        }
428    }
429
430    /// Get a mutable reference to the `GroupsIdx`.
431    ///
432    /// # Panic
433    ///
434    /// panics if the groups are a slice.
435    pub fn idx_mut(&mut self) -> &mut GroupsIdx {
436        match self {
437            GroupsType::Idx(groups) => groups,
438            GroupsType::Slice { .. } => panic!("groups are slices not index"),
439        }
440    }
441
442    pub fn len(&self) -> usize {
443        match self {
444            GroupsType::Idx(groups) => groups.len(),
445            GroupsType::Slice { groups, .. } => groups.len(),
446        }
447    }
448
449    pub fn is_empty(&self) -> bool {
450        self.len() == 0
451    }
452
453    pub fn group_count(&self) -> IdxCa {
454        match self {
455            GroupsType::Idx(groups) => {
456                let ca: NoNull<IdxCa> = groups
457                    .iter()
458                    .map(|(_first, idx)| idx.len() as IdxSize)
459                    .collect_trusted();
460                ca.into_inner()
461            },
462            GroupsType::Slice { groups, .. } => {
463                let ca: NoNull<IdxCa> = groups.iter().map(|[_first, len]| *len).collect_trusted();
464                ca.into_inner()
465            },
466        }
467    }
468    pub fn as_list_chunked(&self) -> ListChunked {
469        match self {
470            GroupsType::Idx(groups) => groups
471                .iter()
472                .map(|(_first, idx)| {
473                    let ca: NoNull<IdxCa> = idx.iter().map(|&v| v as IdxSize).collect();
474                    ca.into_inner().into_series()
475                })
476                .collect_trusted(),
477            GroupsType::Slice { groups, .. } => groups
478                .iter()
479                .map(|&[first, len]| {
480                    let ca: NoNull<IdxCa> = (first..first + len).collect_trusted();
481                    ca.into_inner().into_series()
482                })
483                .collect_trusted(),
484        }
485    }
486
487    pub fn into_sliceable(self) -> GroupPositions {
488        let len = self.len();
489        slice_groups(Arc::new(self), 0, len)
490    }
491}
492
493impl From<GroupsIdx> for GroupsType {
494    fn from(groups: GroupsIdx) -> Self {
495        GroupsType::Idx(groups)
496    }
497}
498
499pub enum GroupsIndicator<'a> {
500    Idx(BorrowIdxItem<'a>),
501    Slice([IdxSize; 2]),
502}
503
504impl GroupsIndicator<'_> {
505    pub fn len(&self) -> usize {
506        match self {
507            GroupsIndicator::Idx(g) => g.1.len(),
508            GroupsIndicator::Slice([_, len]) => *len as usize,
509        }
510    }
511    pub fn first(&self) -> IdxSize {
512        match self {
513            GroupsIndicator::Idx(g) => g.0,
514            GroupsIndicator::Slice([first, _]) => *first,
515        }
516    }
517    pub fn is_empty(&self) -> bool {
518        self.len() == 0
519    }
520}
521
522pub struct GroupsTypeIter<'a> {
523    vals: &'a GroupsType,
524    len: usize,
525    idx: usize,
526}
527
528impl<'a> GroupsTypeIter<'a> {
529    fn new(vals: &'a GroupsType) -> Self {
530        let len = vals.len();
531        let idx = 0;
532        GroupsTypeIter { vals, len, idx }
533    }
534}
535
536impl<'a> Iterator for GroupsTypeIter<'a> {
537    type Item = GroupsIndicator<'a>;
538
539    fn nth(&mut self, n: usize) -> Option<Self::Item> {
540        self.idx = self.idx.saturating_add(n);
541        self.next()
542    }
543
544    fn next(&mut self) -> Option<Self::Item> {
545        if self.idx >= self.len {
546            return None;
547        }
548
549        let out = unsafe {
550            match self.vals {
551                GroupsType::Idx(groups) => {
552                    let item = groups.get_unchecked(self.idx);
553                    Some(GroupsIndicator::Idx(item))
554                },
555                GroupsType::Slice { groups, .. } => {
556                    Some(GroupsIndicator::Slice(*groups.get_unchecked(self.idx)))
557                },
558            }
559        };
560        self.idx += 1;
561        out
562    }
563}
564
565pub struct GroupsTypeParIter<'a> {
566    vals: &'a GroupsType,
567    len: usize,
568}
569
570impl<'a> GroupsTypeParIter<'a> {
571    fn new(vals: &'a GroupsType) -> Self {
572        let len = vals.len();
573        GroupsTypeParIter { vals, len }
574    }
575}
576
577impl<'a> ParallelIterator for GroupsTypeParIter<'a> {
578    type Item = GroupsIndicator<'a>;
579
580    fn drive_unindexed<C>(self, consumer: C) -> C::Result
581    where
582        C: UnindexedConsumer<Self::Item>,
583    {
584        (0..self.len)
585            .into_par_iter()
586            .map(|i| unsafe {
587                match self.vals {
588                    GroupsType::Idx(groups) => GroupsIndicator::Idx(groups.get_unchecked(i)),
589                    GroupsType::Slice { groups, .. } => {
590                        GroupsIndicator::Slice(*groups.get_unchecked(i))
591                    },
592                }
593            })
594            .drive_unindexed(consumer)
595    }
596}
597
598#[derive(Debug)]
599pub struct GroupPositions {
600    // SAFETY: sliced is a shallow clone of original
601    // It emulates a shared reference, not an exclusive reference
602    // Its data must not be mutated through direct access
603    sliced: ManuallyDrop<GroupsType>,
604    // Unsliced buffer
605    original: Arc<GroupsType>,
606    offset: i64,
607    len: usize,
608}
609
610impl Clone for GroupPositions {
611    fn clone(&self) -> Self {
612        let sliced = slice_groups_inner(&self.original, self.offset, self.len);
613
614        Self {
615            sliced,
616            original: self.original.clone(),
617            offset: self.offset,
618            len: self.len,
619        }
620    }
621}
622
623impl PartialEq for GroupPositions {
624    fn eq(&self, other: &Self) -> bool {
625        self.offset == other.offset && self.len == other.len && self.sliced == other.sliced
626    }
627}
628
629impl AsRef<GroupsType> for GroupPositions {
630    fn as_ref(&self) -> &GroupsType {
631        self.sliced.deref()
632    }
633}
634
635impl Deref for GroupPositions {
636    type Target = GroupsType;
637
638    fn deref(&self) -> &Self::Target {
639        self.sliced.deref()
640    }
641}
642
643impl Default for GroupPositions {
644    fn default() -> Self {
645        GroupsType::default().into_sliceable()
646    }
647}
648
649impl GroupPositions {
650    pub fn slice(&self, offset: i64, len: usize) -> Self {
651        let offset = self.offset + offset;
652        slice_groups(
653            self.original.clone(),
654            offset,
655            // invariant that len should be in bounds, so truncate if not
656            if len > self.len { self.len } else { len },
657        )
658    }
659
660    pub fn sort(&mut self) {
661        if !self.as_ref().is_sorted_flag() {
662            let original = Arc::make_mut(&mut self.original);
663            original.sort();
664
665            self.sliced = slice_groups_inner(original, self.offset, self.len);
666        }
667    }
668
669    pub fn unroll(mut self) -> GroupPositions {
670        match self.sliced.deref_mut() {
671            GroupsType::Idx(_) => self,
672            GroupsType::Slice { rolling: false, .. } => self,
673            GroupsType::Slice { groups, .. } => {
674                // SAFETY: sliced is a shallow partial clone of original.
675                // A new owning Vec is required per GH issue #21859
676                let mut cum_offset = 0 as IdxSize;
677                let groups: Vec<_> = groups
678                    .iter()
679                    .map(|[_, len]| {
680                        let new = [cum_offset, *len];
681                        cum_offset += *len;
682                        new
683                    })
684                    .collect();
685
686                GroupsType::Slice {
687                    groups,
688                    rolling: false,
689                }
690                .into_sliceable()
691            },
692        }
693    }
694}
695
696fn slice_groups_inner(g: &GroupsType, offset: i64, len: usize) -> ManuallyDrop<GroupsType> {
697    // SAFETY:
698    // we create new `Vec`s from the sliced groups. But we wrap them in ManuallyDrop
699    // so that we never call drop on them.
700    // These groups lifetimes are bounded to the `g`. This must remain valid
701    // for the scope of the aggregation.
702    match g {
703        GroupsType::Idx(groups) => {
704            let first = unsafe {
705                let first = slice_slice(groups.first(), offset, len);
706                let ptr = first.as_ptr() as *mut _;
707                Vec::from_raw_parts(ptr, first.len(), first.len())
708            };
709
710            let all = unsafe {
711                let all = slice_slice(groups.all(), offset, len);
712                let ptr = all.as_ptr() as *mut _;
713                Vec::from_raw_parts(ptr, all.len(), all.len())
714            };
715            ManuallyDrop::new(GroupsType::Idx(GroupsIdx::new(
716                first,
717                all,
718                groups.is_sorted_flag(),
719            )))
720        },
721        GroupsType::Slice { groups, rolling } => {
722            let groups = unsafe {
723                let groups = slice_slice(groups, offset, len);
724                let ptr = groups.as_ptr() as *mut _;
725                Vec::from_raw_parts(ptr, groups.len(), groups.len())
726            };
727
728            ManuallyDrop::new(GroupsType::Slice {
729                groups,
730                rolling: *rolling,
731            })
732        },
733    }
734}
735
736fn slice_groups(g: Arc<GroupsType>, offset: i64, len: usize) -> GroupPositions {
737    let sliced = slice_groups_inner(g.as_ref(), offset, len);
738
739    GroupPositions {
740        sliced,
741        original: g,
742        offset,
743        len,
744    }
745}
polars_core/frame/group_by/position.rs

polars_core/frame/group_by/
position.rs
