polars_time/
round.rs

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1use arrow::legacy::time_zone::Tz;
2use arrow::temporal_conversions::MILLISECONDS_IN_DAY;
3use polars_core::prelude::arity::broadcast_try_binary_elementwise;
4use polars_core::prelude::*;
5use polars_utils::cache::LruCache;
6
7use crate::prelude::*;
8use crate::truncate::fast_truncate;
9
10#[inline(always)]
11fn fast_round(t: i64, every: i64) -> i64 {
12    fast_truncate(t + every / 2, every)
13}
14
15pub trait PolarsRound {
16    fn round(&self, every: &StringChunked, tz: Option<&Tz>) -> PolarsResult<Self>
17    where
18        Self: Sized;
19}
20
21impl PolarsRound for DatetimeChunked {
22    fn round(&self, every: &StringChunked, tz: Option<&Tz>) -> PolarsResult<Self> {
23        let time_zone = self.time_zone();
24        let offset = Duration::new(0);
25
26        // Let's check if we can use a fastpath...
27        if every.len() == 1 {
28            if let Some(every) = every.get(0) {
29                let every_parsed = Duration::try_parse(every)?;
30                if every_parsed.negative {
31                    polars_bail!(ComputeError: "cannot round a Datetime to a negative duration")
32                }
33                if (time_zone.is_none() || time_zone.as_deref() == Some("UTC"))
34                    && (every_parsed.months() == 0 && every_parsed.weeks() == 0)
35                {
36                    // ... yes we can! Weeks, months, and time zones require extra logic.
37                    // But in this simple case, it's just simple integer arithmetic.
38                    let every = match self.time_unit() {
39                        TimeUnit::Milliseconds => every_parsed.duration_ms(),
40                        TimeUnit::Microseconds => every_parsed.duration_us(),
41                        TimeUnit::Nanoseconds => every_parsed.duration_ns(),
42                    };
43                    return Ok(self
44                        .apply_values(|t| fast_round(t, every))
45                        .into_datetime(self.time_unit(), time_zone.clone()));
46                } else {
47                    let w = Window::new(every_parsed, every_parsed, offset);
48                    let out = match self.time_unit() {
49                        TimeUnit::Milliseconds => {
50                            self.try_apply_nonnull_values_generic(|t| w.round_ms(t, tz))
51                        },
52                        TimeUnit::Microseconds => {
53                            self.try_apply_nonnull_values_generic(|t| w.round_us(t, tz))
54                        },
55                        TimeUnit::Nanoseconds => {
56                            self.try_apply_nonnull_values_generic(|t| w.round_ns(t, tz))
57                        },
58                    };
59                    return Ok(out?.into_datetime(self.time_unit(), self.time_zone().clone()));
60                }
61            } else {
62                return Ok(Int64Chunked::full_null(self.name().clone(), self.len())
63                    .into_datetime(self.time_unit(), self.time_zone().clone()));
64            }
65        }
66
67        polars_ensure!(
68            self.len() == every.len() || self.len() == 1,
69            length_mismatch = "dt.round",
70            self.len(),
71            every.len()
72        );
73
74        // A sqrt(n) cache is not too small, not too large.
75        let mut duration_cache = LruCache::with_capacity((every.len() as f64).sqrt() as usize);
76
77        let func = match self.time_unit() {
78            TimeUnit::Nanoseconds => Window::round_ns,
79            TimeUnit::Microseconds => Window::round_us,
80            TimeUnit::Milliseconds => Window::round_ms,
81        };
82
83        let out = broadcast_try_binary_elementwise(self, every, |opt_timestamp, opt_every| match (
84            opt_timestamp,
85            opt_every,
86        ) {
87            (Some(timestamp), Some(every)) => {
88                let every = *duration_cache.get_or_insert_with(every, Duration::parse);
89
90                if every.negative {
91                    polars_bail!(ComputeError: "cannot round a Datetime to a negative duration")
92                }
93
94                let w = Window::new(every, every, offset);
95                func(&w, timestamp, tz).map(Some)
96            },
97            _ => Ok(None),
98        });
99        Ok(out?.into_datetime(self.time_unit(), self.time_zone().clone()))
100    }
101}
102
103impl PolarsRound for DateChunked {
104    fn round(&self, every: &StringChunked, _tz: Option<&Tz>) -> PolarsResult<Self> {
105        let offset = Duration::new(0);
106        let out = match every.len() {
107            1 => {
108                if let Some(every) = every.get(0) {
109                    let every = Duration::try_parse(every)?;
110                    if every.negative {
111                        polars_bail!(ComputeError: "cannot round a Date to a negative duration")
112                    }
113                    let w = Window::new(every, every, offset);
114                    self.try_apply_nonnull_values_generic(|t| {
115                        Ok(
116                            (w.round_ms(MILLISECONDS_IN_DAY * t as i64, None)?
117                                / MILLISECONDS_IN_DAY) as i32,
118                        )
119                    })
120                } else {
121                    Ok(Int32Chunked::full_null(self.name().clone(), self.len()))
122                }
123            },
124            _ => {
125                polars_ensure!(
126                    self.len() == every.len() || self.len() == 1,
127                    length_mismatch = "dt.round",
128                    self.len(),
129                    every.len()
130                );
131                broadcast_try_binary_elementwise(self, every, |opt_t, opt_every| {
132                    // A sqrt(n) cache is not too small, not too large.
133                    let mut duration_cache =
134                        LruCache::with_capacity((every.len() as f64).sqrt() as usize);
135                    match (opt_t, opt_every) {
136                        (Some(t), Some(every)) => {
137                            let every = *duration_cache.get_or_insert_with(every, Duration::parse);
138
139                            if every.negative {
140                                polars_bail!(ComputeError: "cannot round a Date to a negative duration")
141                            }
142
143                            let w = Window::new(every, every, offset);
144                            Ok(Some(
145                                (w.round_ms(MILLISECONDS_IN_DAY * t as i64, None)?
146                                    / MILLISECONDS_IN_DAY) as i32,
147                            ))
148                        },
149                        _ => Ok(None),
150                    }
151                })
152            },
153        };
154        Ok(out?.into_date())
155    }
156}
polars_time/round.rs

polars_time/
round.rs
