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    /// Checks if groups are of equal length. The caller is responsible for
388    /// updating the groups by calling `groups()` prior to calling this method.
389    pub fn check_lengths(self: &GroupsType, other: &GroupsType) -> PolarsResult<()> {
390        if std::ptr::eq(self, other) {
391            return Ok(());
392        }
393        polars_ensure!(self.iter().zip(other.iter()).all(|(a, b)| {
394            a.len() == b.len()
395        }), ShapeMismatch: "expressions must have matching group lengths");
396        Ok(())
397    }
398
399    /// # Safety
400    /// This will not do any bounds checks. The caller must ensure
401    /// all groups have members.
402    pub unsafe fn take_group_lasts(self) -> Vec<IdxSize> {
403        match self {
404            GroupsType::Idx(groups) => groups
405                .all
406                .iter()
407                .map(|idx| *idx.get_unchecked(idx.len() - 1))
408                .collect(),
409            GroupsType::Slice { groups, .. } => groups
410                .into_iter()
411                .map(|[first, len]| first + len - 1)
412                .collect(),
413        }
414    }
415
416    pub fn par_iter(&self) -> GroupsTypeParIter<'_> {
417        GroupsTypeParIter::new(self)
418    }
419
420    /// Get a reference to the `GroupsIdx`.
421    ///
422    /// # Panic
423    ///
424    /// panics if the groups are a slice.
425    pub fn unwrap_idx(&self) -> &GroupsIdx {
426        match self {
427            GroupsType::Idx(groups) => groups,
428            GroupsType::Slice { .. } => panic!("groups are slices not index"),
429        }
430    }
431
432    /// Get a reference to the `GroupsSlice`.
433    ///
434    /// # Panic
435    ///
436    /// panics if the groups are an idx.
437    pub fn unwrap_slice(&self) -> &GroupsSlice {
438        match self {
439            GroupsType::Slice { groups, .. } => groups,
440            GroupsType::Idx(_) => panic!("groups are index not slices"),
441        }
442    }
443
444    pub fn get(&self, index: usize) -> GroupsIndicator<'_> {
445        match self {
446            GroupsType::Idx(groups) => {
447                let first = groups.first[index];
448                let all = &groups.all[index];
449                GroupsIndicator::Idx((first, all))
450            },
451            GroupsType::Slice { groups, .. } => GroupsIndicator::Slice(groups[index]),
452        }
453    }
454
455    /// Get a mutable reference to the `GroupsIdx`.
456    ///
457    /// # Panic
458    ///
459    /// panics if the groups are a slice.
460    pub fn idx_mut(&mut self) -> &mut GroupsIdx {
461        match self {
462            GroupsType::Idx(groups) => groups,
463            GroupsType::Slice { .. } => panic!("groups are slices not index"),
464        }
465    }
466
467    pub fn len(&self) -> usize {
468        match self {
469            GroupsType::Idx(groups) => groups.len(),
470            GroupsType::Slice { groups, .. } => groups.len(),
471        }
472    }
473
474    pub fn is_empty(&self) -> bool {
475        self.len() == 0
476    }
477
478    pub fn group_count(&self) -> IdxCa {
479        match self {
480            GroupsType::Idx(groups) => {
481                let ca: NoNull<IdxCa> = groups
482                    .iter()
483                    .map(|(_first, idx)| idx.len() as IdxSize)
484                    .collect_trusted();
485                ca.into_inner()
486            },
487            GroupsType::Slice { groups, .. } => {
488                let ca: NoNull<IdxCa> = groups.iter().map(|[_first, len]| *len).collect_trusted();
489                ca.into_inner()
490            },
491        }
492    }
493    pub fn as_list_chunked(&self) -> ListChunked {
494        match self {
495            GroupsType::Idx(groups) => groups
496                .iter()
497                .map(|(_first, idx)| {
498                    let ca: NoNull<IdxCa> = idx.iter().map(|&v| v as IdxSize).collect();
499                    ca.into_inner().into_series()
500                })
501                .collect_trusted(),
502            GroupsType::Slice { groups, .. } => groups
503                .iter()
504                .map(|&[first, len]| {
505                    let ca: NoNull<IdxCa> = (first..first + len).collect_trusted();
506                    ca.into_inner().into_series()
507                })
508                .collect_trusted(),
509        }
510    }
511
512    pub fn into_sliceable(self) -> GroupPositions {
513        let len = self.len();
514        slice_groups(Arc::new(self), 0, len)
515    }
516}
517
518impl From<GroupsIdx> for GroupsType {
519    fn from(groups: GroupsIdx) -> Self {
520        GroupsType::Idx(groups)
521    }
522}
523
524pub enum GroupsIndicator<'a> {
525    Idx(BorrowIdxItem<'a>),
526    Slice([IdxSize; 2]),
527}
528
529impl GroupsIndicator<'_> {
530    pub fn len(&self) -> usize {
531        match self {
532            GroupsIndicator::Idx(g) => g.1.len(),
533            GroupsIndicator::Slice([_, len]) => *len as usize,
534        }
535    }
536    pub fn first(&self) -> IdxSize {
537        match self {
538            GroupsIndicator::Idx(g) => g.0,
539            GroupsIndicator::Slice([first, _]) => *first,
540        }
541    }
542    pub fn is_empty(&self) -> bool {
543        self.len() == 0
544    }
545}
546
547pub struct GroupsTypeIter<'a> {
548    vals: &'a GroupsType,
549    len: usize,
550    idx: usize,
551}
552
553impl<'a> GroupsTypeIter<'a> {
554    fn new(vals: &'a GroupsType) -> Self {
555        let len = vals.len();
556        let idx = 0;
557        GroupsTypeIter { vals, len, idx }
558    }
559}
560
561impl<'a> Iterator for GroupsTypeIter<'a> {
562    type Item = GroupsIndicator<'a>;
563
564    fn nth(&mut self, n: usize) -> Option<Self::Item> {
565        self.idx = self.idx.saturating_add(n);
566        self.next()
567    }
568
569    fn next(&mut self) -> Option<Self::Item> {
570        if self.idx >= self.len {
571            return None;
572        }
573
574        let out = unsafe {
575            match self.vals {
576                GroupsType::Idx(groups) => {
577                    let item = groups.get_unchecked(self.idx);
578                    Some(GroupsIndicator::Idx(item))
579                },
580                GroupsType::Slice { groups, .. } => {
581                    Some(GroupsIndicator::Slice(*groups.get_unchecked(self.idx)))
582                },
583            }
584        };
585        self.idx += 1;
586        out
587    }
588}
589
590pub struct GroupsTypeParIter<'a> {
591    vals: &'a GroupsType,
592    len: usize,
593}
594
595impl<'a> GroupsTypeParIter<'a> {
596    fn new(vals: &'a GroupsType) -> Self {
597        let len = vals.len();
598        GroupsTypeParIter { vals, len }
599    }
600}
601
602impl<'a> ParallelIterator for GroupsTypeParIter<'a> {
603    type Item = GroupsIndicator<'a>;
604
605    fn drive_unindexed<C>(self, consumer: C) -> C::Result
606    where
607        C: UnindexedConsumer<Self::Item>,
608    {
609        (0..self.len)
610            .into_par_iter()
611            .map(|i| unsafe {
612                match self.vals {
613                    GroupsType::Idx(groups) => GroupsIndicator::Idx(groups.get_unchecked(i)),
614                    GroupsType::Slice { groups, .. } => {
615                        GroupsIndicator::Slice(*groups.get_unchecked(i))
616                    },
617                }
618            })
619            .drive_unindexed(consumer)
620    }
621}
622
623#[derive(Debug)]
624pub struct GroupPositions {
625    // SAFETY: sliced is a shallow clone of original
626    // It emulates a shared reference, not an exclusive reference
627    // Its data must not be mutated through direct access
628    sliced: ManuallyDrop<GroupsType>,
629    // Unsliced buffer
630    original: Arc<GroupsType>,
631    offset: i64,
632    len: usize,
633}
634
635impl Clone for GroupPositions {
636    fn clone(&self) -> Self {
637        let sliced = slice_groups_inner(&self.original, self.offset, self.len);
638
639        Self {
640            sliced,
641            original: self.original.clone(),
642            offset: self.offset,
643            len: self.len,
644        }
645    }
646}
647
648impl AsRef<GroupsType> for GroupPositions {
649    fn as_ref(&self) -> &GroupsType {
650        self.sliced.deref()
651    }
652}
653
654impl Deref for GroupPositions {
655    type Target = GroupsType;
656
657    fn deref(&self) -> &Self::Target {
658        self.sliced.deref()
659    }
660}
661
662impl Default for GroupPositions {
663    fn default() -> Self {
664        GroupsType::default().into_sliceable()
665    }
666}
667
668impl GroupPositions {
669    pub fn slice(&self, offset: i64, len: usize) -> Self {
670        let offset = self.offset + offset;
671        slice_groups(
672            self.original.clone(),
673            offset,
674            // invariant that len should be in bounds, so truncate if not
675            if len > self.len { self.len } else { len },
676        )
677    }
678
679    pub fn sort(&mut self) {
680        if !self.as_ref().is_sorted_flag() {
681            let original = Arc::make_mut(&mut self.original);
682            original.sort();
683
684            self.sliced = slice_groups_inner(original, self.offset, self.len);
685        }
686    }
687
688    pub fn unroll(mut self) -> GroupPositions {
689        match self.sliced.deref_mut() {
690            GroupsType::Idx(_) => self,
691            GroupsType::Slice {
692                overlapping: false, ..
693            } => self,
694            GroupsType::Slice { groups, .. } => {
695                // SAFETY: sliced is a shallow partial clone of original.
696                // A new owning Vec is required per GH issue #21859
697                let mut cum_offset = 0 as IdxSize;
698                let groups: Vec<_> = groups
699                    .iter()
700                    .map(|[_, len]| {
701                        let new = [cum_offset, *len];
702                        cum_offset += *len;
703                        new
704                    })
705                    .collect();
706
707                GroupsType::Slice {
708                    groups,
709                    overlapping: false,
710                }
711                .into_sliceable()
712            },
713        }
714    }
715
716    pub fn as_unrolled_slice(&self) -> Option<&GroupsSlice> {
717        match &*self.sliced {
718            GroupsType::Idx(_) => None,
719            GroupsType::Slice {
720                overlapping: true, ..
721            } => None,
722            GroupsType::Slice {
723                groups,
724                overlapping: false,
725            } => Some(groups),
726        }
727    }
728}
729
730fn slice_groups_inner(g: &GroupsType, offset: i64, len: usize) -> ManuallyDrop<GroupsType> {
731    // SAFETY:
732    // we create new `Vec`s from the sliced groups. But we wrap them in ManuallyDrop
733    // so that we never call drop on them.
734    // These groups lifetimes are bounded to the `g`. This must remain valid
735    // for the scope of the aggregation.
736    match g {
737        GroupsType::Idx(groups) => {
738            let first = unsafe {
739                let first = slice_slice(groups.first(), offset, len);
740                let ptr = first.as_ptr() as *mut _;
741                Vec::from_raw_parts(ptr, first.len(), first.len())
742            };
743
744            let all = unsafe {
745                let all = slice_slice(groups.all(), offset, len);
746                let ptr = all.as_ptr() as *mut _;
747                Vec::from_raw_parts(ptr, all.len(), all.len())
748            };
749            ManuallyDrop::new(GroupsType::Idx(GroupsIdx::new(
750                first,
751                all,
752                groups.is_sorted_flag(),
753            )))
754        },
755        GroupsType::Slice {
756            groups,
757            overlapping,
758        } => {
759            let groups = unsafe {
760                let groups = slice_slice(groups, offset, len);
761                let ptr = groups.as_ptr() as *mut _;
762                Vec::from_raw_parts(ptr, groups.len(), groups.len())
763            };
764
765            ManuallyDrop::new(GroupsType::Slice {
766                groups,
767                overlapping: *overlapping,
768            })
769        },
770    }
771}
772
773fn slice_groups(g: Arc<GroupsType>, offset: i64, len: usize) -> GroupPositions {
774    let sliced = slice_groups_inner(g.as_ref(), offset, len);
775
776    GroupPositions {
777        sliced,
778        original: g,
779        offset,
780        len,
781    }
782}
polars_core/frame/group_by/position.rs

polars_core/frame/group_by/
position.rs
