polars_time/
truncate.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::*;
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_deref() == Some("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                        .apply_values(|t| fast_truncate(t, every))
52                        .into_datetime(self.time_unit(), time_zone.clone()));
53                } else {
54                    let w = Window::new(every_parsed, every_parsed, offset);
55                    let out = match self.time_unit() {
56                        TimeUnit::Milliseconds => {
57                            self.try_apply_nonnull_values_generic(|t| w.truncate_ms(t, tz))
58                        },
59                        TimeUnit::Microseconds => {
60                            self.try_apply_nonnull_values_generic(|t| w.truncate_us(t, tz))
61                        },
62                        TimeUnit::Nanoseconds => {
63                            self.try_apply_nonnull_values_generic(|t| w.truncate_ns(t, tz))
64                        },
65                    };
66                    return Ok(out?.into_datetime(self.time_unit(), self.time_zone().clone()));
67                }
68            } else {
69                return Ok(Int64Chunked::full_null(self.name().clone(), self.len())
70                    .into_datetime(self.time_unit(), self.time_zone().clone()));
71            }
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::truncate_ns,
79            TimeUnit::Microseconds => Window::truncate_us,
80            TimeUnit::Milliseconds => Window::truncate_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 truncate 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 PolarsTruncate for DateChunked {
104    fn truncate(&self, _tz: Option<&Tz>, every: &StringChunked) -> PolarsResult<Self> {
105        polars_ensure!(
106            self.len() == every.len() || self.len() == 1 || every.len() == 1,
107            length_mismatch = "dt.truncate",
108            self.len(),
109            every.len()
110        );
111
112        let offset = Duration::new(0);
113        let out = match every.len() {
114            1 => {
115                if let Some(every) = every.get(0) {
116                    let every = Duration::parse(every);
117                    if every.negative {
118                        polars_bail!(ComputeError: "cannot truncate a Date to a negative duration")
119                    }
120                    let w = Window::new(every, every, offset);
121                    self.try_apply_nonnull_values_generic(|t| {
122                        Ok((w.truncate_ms(MILLISECONDS_IN_DAY * t as i64, None)?
123                            / MILLISECONDS_IN_DAY) as i32)
124                    })
125                } else {
126                    Ok(Int32Chunked::full_null(self.name().clone(), self.len()))
127                }
128            },
129            _ => broadcast_try_binary_elementwise(self, every, |opt_t, opt_every| {
130                // A sqrt(n) cache is not too small, not too large.
131                let mut duration_cache =
132                    LruCache::with_capacity((every.len() as f64).sqrt() as usize);
133                match (opt_t, opt_every) {
134                    (Some(t), Some(every)) => {
135                        let every = *duration_cache.get_or_insert_with(every, Duration::parse);
136
137                        if every.negative {
138                            polars_bail!(ComputeError: "cannot truncate a Date to a negative duration")
139                        }
140
141                        let w = Window::new(every, every, offset);
142                        Ok(Some(
143                            (w.truncate_ms(MILLISECONDS_IN_DAY * t as i64, None)?
144                                / MILLISECONDS_IN_DAY) as i32,
145                        ))
146                    },
147                    _ => Ok(None),
148                }
149            }),
150        };
151        Ok(out?.into_date())
152    }
153}
polars_time/truncate.rs

polars_time/
truncate.rs
