polars_time/
truncate.rs

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

polars_time/
truncate.rs
