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 the groups may overlap, as is typically the case with `rolling`
260        // or `dynamic_group_by`.
261        // Example use cases: avoid memory explosion when calling aggregation; unroll groups
262        // when exploding an aggregated list with overlapping groups.
263        overlapping: bool,
264    },
265}
266
267impl Default for GroupsType {
268    fn default() -> Self {
269        GroupsType::Idx(GroupsIdx::default())
270    }
271}
272
273impl GroupsType {
274    pub fn into_idx(self) -> GroupsIdx {
275        match self {
276            GroupsType::Idx(groups) => groups,
277            GroupsType::Slice { groups, .. } => {
278                polars_warn!(
279                    "Had to reallocate groups, missed an optimization opportunity. Please open an issue."
280                );
281                groups
282                    .iter()
283                    .map(|&[first, len]| (first, (first..first + len).collect::<IdxVec>()))
284                    .collect()
285            },
286        }
287    }
288
289    pub(crate) fn prepare_list_agg(
290        &self,
291        total_len: usize,
292    ) -> (Option<IdxCa>, OffsetsBuffer<i64>, bool) {
293        let mut can_fast_explode = true;
294        match self {
295            GroupsType::Idx(groups) => {
296                let mut list_offset = Vec::with_capacity(self.len() + 1);
297                let mut gather_offsets = Vec::with_capacity(total_len);
298
299                let mut len_so_far = 0i64;
300                list_offset.push(len_so_far);
301
302                for idx in groups {
303                    let idx = idx.1;
304                    gather_offsets.extend_from_slice(idx);
305                    len_so_far += idx.len() as i64;
306                    list_offset.push(len_so_far);
307                    can_fast_explode &= !idx.is_empty();
308                }
309                unsafe {
310                    (
311                        Some(IdxCa::from_vec(PlSmallStr::EMPTY, gather_offsets)),
312                        OffsetsBuffer::new_unchecked(list_offset.into()),
313                        can_fast_explode,
314                    )
315                }
316            },
317            GroupsType::Slice { groups, .. } => {
318                let mut list_offset = Vec::with_capacity(self.len() + 1);
319                let mut gather_offsets = Vec::with_capacity(total_len);
320                let mut len_so_far = 0i64;
321                list_offset.push(len_so_far);
322
323                for g in groups {
324                    let len = g[1];
325                    let offset = g[0];
326                    gather_offsets.extend(offset..offset + len);
327
328                    len_so_far += len as i64;
329                    list_offset.push(len_so_far);
330                    can_fast_explode &= len > 0;
331                }
332
333                unsafe {
334                    (
335                        Some(IdxCa::from_vec(PlSmallStr::EMPTY, gather_offsets)),
336                        OffsetsBuffer::new_unchecked(list_offset.into()),
337                        can_fast_explode,
338                    )
339                }
340            },
341        }
342    }
343
344    pub fn iter(&self) -> GroupsTypeIter<'_> {
345        GroupsTypeIter::new(self)
346    }
347
348    pub fn sort(&mut self) {
349        match self {
350            GroupsType::Idx(groups) => {
351                if !groups.is_sorted_flag() {
352                    groups.sort()
353                }
354            },
355            GroupsType::Slice { .. } => {
356                // invariant of the type
357            },
358        }
359    }
360
361    pub(crate) fn is_sorted_flag(&self) -> bool {
362        match self {
363            GroupsType::Idx(groups) => groups.is_sorted_flag(),
364            GroupsType::Slice { .. } => true,
365        }
366    }
367
368    pub fn is_overlapping(&self) -> bool {
369        matches!(
370            self,
371            GroupsType::Slice {
372                overlapping: true,
373                ..
374            }
375        )
376    }
377
378    pub fn take_group_firsts(self) -> Vec<IdxSize> {
379        match self {
380            GroupsType::Idx(mut groups) => std::mem::take(&mut groups.first),
381            GroupsType::Slice { groups, .. } => {
382                groups.into_iter().map(|[first, _len]| first).collect()
383            },
384        }
385    }
386
387    /// # Safety
388    /// This will not do any bounds checks. The caller must ensure
389    /// all groups have members.
390    pub unsafe fn take_group_lasts(self) -> Vec<IdxSize> {
391        match self {
392            GroupsType::Idx(groups) => groups
393                .all
394                .iter()
395                .map(|idx| *idx.get_unchecked(idx.len() - 1))
396                .collect(),
397            GroupsType::Slice { groups, .. } => groups
398                .into_iter()
399                .map(|[first, len]| first + len - 1)
400                .collect(),
401        }
402    }
403
404    pub fn par_iter(&self) -> GroupsTypeParIter<'_> {
405        GroupsTypeParIter::new(self)
406    }
407
408    /// Get a reference to the `GroupsIdx`.
409    ///
410    /// # Panic
411    ///
412    /// panics if the groups are a slice.
413    pub fn unwrap_idx(&self) -> &GroupsIdx {
414        match self {
415            GroupsType::Idx(groups) => groups,
416            GroupsType::Slice { .. } => panic!("groups are slices not index"),
417        }
418    }
419
420    /// Get a reference to the `GroupsSlice`.
421    ///
422    /// # Panic
423    ///
424    /// panics if the groups are an idx.
425    pub fn unwrap_slice(&self) -> &GroupsSlice {
426        match self {
427            GroupsType::Slice { groups, .. } => groups,
428            GroupsType::Idx(_) => panic!("groups are index not slices"),
429        }
430    }
431
432    pub fn get(&self, index: usize) -> GroupsIndicator<'_> {
433        match self {
434            GroupsType::Idx(groups) => {
435                let first = groups.first[index];
436                let all = &groups.all[index];
437                GroupsIndicator::Idx((first, all))
438            },
439            GroupsType::Slice { groups, .. } => GroupsIndicator::Slice(groups[index]),
440        }
441    }
442
443    /// Get a mutable reference to the `GroupsIdx`.
444    ///
445    /// # Panic
446    ///
447    /// panics if the groups are a slice.
448    pub fn idx_mut(&mut self) -> &mut GroupsIdx {
449        match self {
450            GroupsType::Idx(groups) => groups,
451            GroupsType::Slice { .. } => panic!("groups are slices not index"),
452        }
453    }
454
455    pub fn len(&self) -> usize {
456        match self {
457            GroupsType::Idx(groups) => groups.len(),
458            GroupsType::Slice { groups, .. } => groups.len(),
459        }
460    }
461
462    pub fn is_empty(&self) -> bool {
463        self.len() == 0
464    }
465
466    pub fn group_count(&self) -> IdxCa {
467        match self {
468            GroupsType::Idx(groups) => {
469                let ca: NoNull<IdxCa> = groups
470                    .iter()
471                    .map(|(_first, idx)| idx.len() as IdxSize)
472                    .collect_trusted();
473                ca.into_inner()
474            },
475            GroupsType::Slice { groups, .. } => {
476                let ca: NoNull<IdxCa> = groups.iter().map(|[_first, len]| *len).collect_trusted();
477                ca.into_inner()
478            },
479        }
480    }
481    pub fn as_list_chunked(&self) -> ListChunked {
482        match self {
483            GroupsType::Idx(groups) => groups
484                .iter()
485                .map(|(_first, idx)| {
486                    let ca: NoNull<IdxCa> = idx.iter().map(|&v| v as IdxSize).collect();
487                    ca.into_inner().into_series()
488                })
489                .collect_trusted(),
490            GroupsType::Slice { groups, .. } => groups
491                .iter()
492                .map(|&[first, len]| {
493                    let ca: NoNull<IdxCa> = (first..first + len).collect_trusted();
494                    ca.into_inner().into_series()
495                })
496                .collect_trusted(),
497        }
498    }
499
500    pub fn into_sliceable(self) -> GroupPositions {
501        let len = self.len();
502        slice_groups(Arc::new(self), 0, len)
503    }
504
505    pub fn check_lengths(self: &GroupsType, other: &GroupsType) -> PolarsResult<()> {
506        if std::ptr::eq(self, other) {
507            return Ok(());
508        }
509        polars_ensure!(self.iter().zip(other.iter()).all(|(a, b)| {
510            a.len() == b.len()
511        }), ComputeError: "expressions must have matching group lengths");
512        Ok(())
513    }
514}
515
516impl From<GroupsIdx> for GroupsType {
517    fn from(groups: GroupsIdx) -> Self {
518        GroupsType::Idx(groups)
519    }
520}
521
522pub enum GroupsIndicator<'a> {
523    Idx(BorrowIdxItem<'a>),
524    Slice([IdxSize; 2]),
525}
526
527impl GroupsIndicator<'_> {
528    pub fn len(&self) -> usize {
529        match self {
530            GroupsIndicator::Idx(g) => g.1.len(),
531            GroupsIndicator::Slice([_, len]) => *len as usize,
532        }
533    }
534    pub fn first(&self) -> IdxSize {
535        match self {
536            GroupsIndicator::Idx(g) => g.0,
537            GroupsIndicator::Slice([first, _]) => *first,
538        }
539    }
540    pub fn is_empty(&self) -> bool {
541        self.len() == 0
542    }
543}
544
545pub struct GroupsTypeIter<'a> {
546    vals: &'a GroupsType,
547    len: usize,
548    idx: usize,
549}
550
551impl<'a> GroupsTypeIter<'a> {
552    fn new(vals: &'a GroupsType) -> Self {
553        let len = vals.len();
554        let idx = 0;
555        GroupsTypeIter { vals, len, idx }
556    }
557}
558
559impl<'a> Iterator for GroupsTypeIter<'a> {
560    type Item = GroupsIndicator<'a>;
561
562    fn nth(&mut self, n: usize) -> Option<Self::Item> {
563        self.idx = self.idx.saturating_add(n);
564        self.next()
565    }
566
567    fn next(&mut self) -> Option<Self::Item> {
568        if self.idx >= self.len {
569            return None;
570        }
571
572        let out = unsafe {
573            match self.vals {
574                GroupsType::Idx(groups) => {
575                    let item = groups.get_unchecked(self.idx);
576                    Some(GroupsIndicator::Idx(item))
577                },
578                GroupsType::Slice { groups, .. } => {
579                    Some(GroupsIndicator::Slice(*groups.get_unchecked(self.idx)))
580                },
581            }
582        };
583        self.idx += 1;
584        out
585    }
586}
587
588pub struct GroupsTypeParIter<'a> {
589    vals: &'a GroupsType,
590    len: usize,
591}
592
593impl<'a> GroupsTypeParIter<'a> {
594    fn new(vals: &'a GroupsType) -> Self {
595        let len = vals.len();
596        GroupsTypeParIter { vals, len }
597    }
598}
599
600impl<'a> ParallelIterator for GroupsTypeParIter<'a> {
601    type Item = GroupsIndicator<'a>;
602
603    fn drive_unindexed<C>(self, consumer: C) -> C::Result
604    where
605        C: UnindexedConsumer<Self::Item>,
606    {
607        (0..self.len)
608            .into_par_iter()
609            .map(|i| unsafe {
610                match self.vals {
611                    GroupsType::Idx(groups) => GroupsIndicator::Idx(groups.get_unchecked(i)),
612                    GroupsType::Slice { groups, .. } => {
613                        GroupsIndicator::Slice(*groups.get_unchecked(i))
614                    },
615                }
616            })
617            .drive_unindexed(consumer)
618    }
619}
620
621#[derive(Debug)]
622pub struct GroupPositions {
623    // SAFETY: sliced is a shallow clone of original
624    // It emulates a shared reference, not an exclusive reference
625    // Its data must not be mutated through direct access
626    sliced: ManuallyDrop<GroupsType>,
627    // Unsliced buffer
628    original: Arc<GroupsType>,
629    offset: i64,
630    len: usize,
631}
632
633impl Clone for GroupPositions {
634    fn clone(&self) -> Self {
635        let sliced = slice_groups_inner(&self.original, self.offset, self.len);
636
637        Self {
638            sliced,
639            original: self.original.clone(),
640            offset: self.offset,
641            len: self.len,
642        }
643    }
644}
645
646impl PartialEq for GroupPositions {
647    fn eq(&self, other: &Self) -> bool {
648        self.offset == other.offset && self.len == other.len && self.sliced == other.sliced
649    }
650}
651
652impl AsRef<GroupsType> for GroupPositions {
653    fn as_ref(&self) -> &GroupsType {
654        self.sliced.deref()
655    }
656}
657
658impl Deref for GroupPositions {
659    type Target = GroupsType;
660
661    fn deref(&self) -> &Self::Target {
662        self.sliced.deref()
663    }
664}
665
666impl Default for GroupPositions {
667    fn default() -> Self {
668        GroupsType::default().into_sliceable()
669    }
670}
671
672impl GroupPositions {
673    pub fn slice(&self, offset: i64, len: usize) -> Self {
674        let offset = self.offset + offset;
675        slice_groups(
676            self.original.clone(),
677            offset,
678            // invariant that len should be in bounds, so truncate if not
679            if len > self.len { self.len } else { len },
680        )
681    }
682
683    pub fn sort(&mut self) {
684        if !self.as_ref().is_sorted_flag() {
685            let original = Arc::make_mut(&mut self.original);
686            original.sort();
687
688            self.sliced = slice_groups_inner(original, self.offset, self.len);
689        }
690    }
691
692    pub fn unroll(mut self) -> GroupPositions {
693        match self.sliced.deref_mut() {
694            GroupsType::Idx(_) => self,
695            GroupsType::Slice {
696                overlapping: false, ..
697            } => self,
698            GroupsType::Slice { groups, .. } => {
699                // SAFETY: sliced is a shallow partial clone of original.
700                // A new owning Vec is required per GH issue #21859
701                let mut cum_offset = 0 as IdxSize;
702                let groups: Vec<_> = groups
703                    .iter()
704                    .map(|[_, len]| {
705                        let new = [cum_offset, *len];
706                        cum_offset += *len;
707                        new
708                    })
709                    .collect();
710
711                GroupsType::Slice {
712                    groups,
713                    overlapping: false,
714                }
715                .into_sliceable()
716            },
717        }
718    }
719
720    pub fn as_unrolled_slice(&self) -> Option<&GroupsSlice> {
721        match &*self.sliced {
722            GroupsType::Idx(_) => None,
723            GroupsType::Slice {
724                overlapping: true, ..
725            } => None,
726            GroupsType::Slice {
727                groups,
728                overlapping: false,
729            } => Some(groups),
730        }
731    }
732}
733
734fn slice_groups_inner(g: &GroupsType, offset: i64, len: usize) -> ManuallyDrop<GroupsType> {
735    // SAFETY:
736    // we create new `Vec`s from the sliced groups. But we wrap them in ManuallyDrop
737    // so that we never call drop on them.
738    // These groups lifetimes are bounded to the `g`. This must remain valid
739    // for the scope of the aggregation.
740    match g {
741        GroupsType::Idx(groups) => {
742            let first = unsafe {
743                let first = slice_slice(groups.first(), offset, len);
744                let ptr = first.as_ptr() as *mut _;
745                Vec::from_raw_parts(ptr, first.len(), first.len())
746            };
747
748            let all = unsafe {
749                let all = slice_slice(groups.all(), offset, len);
750                let ptr = all.as_ptr() as *mut _;
751                Vec::from_raw_parts(ptr, all.len(), all.len())
752            };
753            ManuallyDrop::new(GroupsType::Idx(GroupsIdx::new(
754                first,
755                all,
756                groups.is_sorted_flag(),
757            )))
758        },
759        GroupsType::Slice {
760            groups,
761            overlapping,
762        } => {
763            let groups = unsafe {
764                let groups = slice_slice(groups, offset, len);
765                let ptr = groups.as_ptr() as *mut _;
766                Vec::from_raw_parts(ptr, groups.len(), groups.len())
767            };
768
769            ManuallyDrop::new(GroupsType::Slice {
770                groups,
771                overlapping: *overlapping,
772            })
773        },
774    }
775}
776
777fn slice_groups(g: Arc<GroupsType>, offset: i64, len: usize) -> GroupPositions {
778    let sliced = slice_groups_inner(g.as_ref(), offset, len);
779
780    GroupPositions {
781        sliced,
782        original: g,
783        offset,
784        len,
785    }
786}
polars_core/frame/group_by/position.rs

polars_core/frame/group_by/
position.rs
