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// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements. See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership. The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License. You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied. See the License for the
// specific language governing permissions and limitations
// under the License.
use crate::error::{ArrowError, Result};
use chrono::{prelude::*, LocalResult};
/// Accepts a string in RFC3339 / ISO8601 standard format and some
/// variants and converts it to a nanosecond precision timestamp.
///
/// Implements the `to_timestamp` function to convert a string to a
/// timestamp, following the model of spark SQL’s to_`timestamp`.
///
/// In addition to RFC3339 / ISO8601 standard timestamps, it also
/// accepts strings that use a space ` ` to separate the date and time
/// as well as strings that have no explicit timezone offset.
///
/// Examples of accepted inputs:
/// * `1997-01-31T09:26:56.123Z` # RCF3339
/// * `1997-01-31T09:26:56.123-05:00` # RCF3339
/// * `1997-01-31 09:26:56.123-05:00` # close to RCF3339 but with a space rather than T
/// * `1997-01-31T09:26:56.123` # close to RCF3339 but no timezone offset specified
/// * `1997-01-31 09:26:56.123` # close to RCF3339 but uses a space and no timezone offset
/// * `1997-01-31 09:26:56` # close to RCF3339, no fractional seconds
//
/// Internally, this function uses the `chrono` library for the
/// datetime parsing
///
/// We hope to extend this function in the future with a second
/// parameter to specifying the format string.
///
/// ## Timestamp Precision
///
/// Function uses the maximum precision timestamps supported by
/// Arrow (nanoseconds stored as a 64-bit integer) timestamps. This
/// means the range of dates that timestamps can represent is ~1677 AD
/// to 2262 AM
///
///
/// ## Timezone / Offset Handling
///
/// Numerical values of timestamps are stored compared to offset UTC.
///
/// This function interprets strings without an explicit time zone as
/// timestamps with offsets of the local time on the machine
///
/// For example, `1997-01-31 09:26:56.123Z` is interpreted as UTC, as
/// it has an explicit timezone specifier (“Z” for Zulu/UTC)
///
/// `1997-01-31T09:26:56.123` is interpreted as a local timestamp in
/// the timezone of the machine. For example, if
/// the system timezone is set to Americas/New_York (UTC-5) the
/// timestamp will be interpreted as though it were
/// `1997-01-31T09:26:56.123-05:00`
#[inline]
pub fn string_to_timestamp_nanos(s: &str) -> Result<i64> {
// Fast path: RFC3339 timestamp (with a T)
// Example: 2020-09-08T13:42:29.190855Z
if let Ok(ts) = DateTime::parse_from_rfc3339(s) {
return Ok(ts.timestamp_nanos());
}
// Implement quasi-RFC3339 support by trying to parse the
// timestamp with various other format specifiers to to support
// separating the date and time with a space ' ' rather than 'T' to be
// (more) compatible with Apache Spark SQL
// timezone offset, using ' ' as a separator
// Example: 2020-09-08 13:42:29.190855-05:00
if let Ok(ts) = DateTime::parse_from_str(s, "%Y-%m-%d %H:%M:%S%.f%:z") {
return Ok(ts.timestamp_nanos());
}
// with an explicit Z, using ' ' as a separator
// Example: 2020-09-08 13:42:29Z
if let Ok(ts) = Utc.datetime_from_str(s, "%Y-%m-%d %H:%M:%S%.fZ") {
return Ok(ts.timestamp_nanos());
}
// Support timestamps without an explicit timezone offset, again
// to be compatible with what Apache Spark SQL does.
// without a timezone specifier as a local time, using T as a separator
// Example: 2020-09-08T13:42:29.190855
if let Ok(ts) = NaiveDateTime::parse_from_str(s, "%Y-%m-%dT%H:%M:%S%.f") {
return naive_datetime_to_timestamp(s, ts);
}
// without a timezone specifier as a local time, using T as a
// separator, no fractional seconds
// Example: 2020-09-08T13:42:29
if let Ok(ts) = NaiveDateTime::parse_from_str(s, "%Y-%m-%dT%H:%M:%S") {
return naive_datetime_to_timestamp(s, ts);
}
// without a timezone specifier as a local time, using ' ' as a separator
// Example: 2020-09-08 13:42:29.190855
if let Ok(ts) = NaiveDateTime::parse_from_str(s, "%Y-%m-%d %H:%M:%S%.f") {
return naive_datetime_to_timestamp(s, ts);
}
// without a timezone specifier as a local time, using ' ' as a
// separator, no fractional seconds
// Example: 2020-09-08 13:42:29
if let Ok(ts) = NaiveDateTime::parse_from_str(s, "%Y-%m-%d %H:%M:%S") {
return naive_datetime_to_timestamp(s, ts);
}
// Note we don't pass along the error message from the underlying
// chrono parsing because we tried several different format
// strings and we don't know which the user was trying to
// match. Ths any of the specific error messages is likely to be
// be more confusing than helpful
Err(ArrowError::CastError(format!(
"Error parsing '{}' as timestamp",
s
)))
}
/// Converts the naive datetime (which has no specific timezone) to a
/// nanosecond epoch timestamp relative to UTC.
fn naive_datetime_to_timestamp(s: &str, datetime: NaiveDateTime) -> Result<i64> {
let l = Local {};
match l.from_local_datetime(&datetime) {
LocalResult::None => Err(ArrowError::CastError(format!(
"Error parsing '{}' as timestamp: local time representation is invalid",
s
))),
LocalResult::Single(local_datetime) => {
Ok(local_datetime.with_timezone(&Utc).timestamp_nanos())
}
// Ambiguous times can happen if the timestamp is exactly when
// a daylight savings time transition occurs, for example, and
// so the datetime could validly be said to be in two
// potential offsets. However, since we are about to convert
// to UTC anyways, we can pick one arbitrarily
LocalResult::Ambiguous(local_datetime, _) => {
Ok(local_datetime.with_timezone(&Utc).timestamp_nanos())
}
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn string_to_timestamp_timezone() -> Result<()> {
// Explicit timezone
assert_eq!(
1599572549190855000,
parse_timestamp("2020-09-08T13:42:29.190855+00:00")?
);
assert_eq!(
1599572549190855000,
parse_timestamp("2020-09-08T13:42:29.190855Z")?
);
assert_eq!(
1599572549000000000,
parse_timestamp("2020-09-08T13:42:29Z")?
); // no fractional part
assert_eq!(
1599590549190855000,
parse_timestamp("2020-09-08T13:42:29.190855-05:00")?
);
Ok(())
}
#[test]
fn string_to_timestamp_timezone_space() -> Result<()> {
// Ensure space rather than T between time and date is accepted
assert_eq!(
1599572549190855000,
parse_timestamp("2020-09-08 13:42:29.190855+00:00")?
);
assert_eq!(
1599572549190855000,
parse_timestamp("2020-09-08 13:42:29.190855Z")?
);
assert_eq!(
1599572549000000000,
parse_timestamp("2020-09-08 13:42:29Z")?
); // no fractional part
assert_eq!(
1599590549190855000,
parse_timestamp("2020-09-08 13:42:29.190855-05:00")?
);
Ok(())
}
/// Interprets a naive_datetime (with no explicit timezone offset)
/// using the local timezone and returns the timestamp in UTC (0
/// offset)
fn naive_datetime_to_timestamp(naive_datetime: &NaiveDateTime) -> i64 {
// Note: Use chrono APIs that are different than
// naive_datetime_to_timestamp to compute the utc offset to
// try and double check the logic
let utc_offset_secs = match Local.offset_from_local_datetime(naive_datetime) {
LocalResult::Single(local_offset) => {
local_offset.fix().local_minus_utc() as i64
}
_ => panic!("Unexpected failure converting to local datetime"),
};
let utc_offset_nanos = utc_offset_secs * 1_000_000_000;
naive_datetime.timestamp_nanos() - utc_offset_nanos
}
#[test]
#[cfg_attr(miri, ignore)] // unsupported operation: can't call foreign function: mktime
fn string_to_timestamp_no_timezone() -> Result<()> {
// This test is designed to succeed in regardless of the local
// timezone the test machine is running. Thus it is still
// somewhat susceptible to bugs in the use of chrono
let naive_datetime = NaiveDateTime::new(
NaiveDate::from_ymd(2020, 9, 8),
NaiveTime::from_hms_nano(13, 42, 29, 190855000),
);
// Ensure both T and ' ' variants work
assert_eq!(
naive_datetime_to_timestamp(&naive_datetime),
parse_timestamp("2020-09-08T13:42:29.190855")?
);
assert_eq!(
naive_datetime_to_timestamp(&naive_datetime),
parse_timestamp("2020-09-08 13:42:29.190855")?
);
// Also ensure that parsing timestamps with no fractional
// second part works as well
let naive_datetime_whole_secs = NaiveDateTime::new(
NaiveDate::from_ymd(2020, 9, 8),
NaiveTime::from_hms(13, 42, 29),
);
// Ensure both T and ' ' variants work
assert_eq!(
naive_datetime_to_timestamp(&naive_datetime_whole_secs),
parse_timestamp("2020-09-08T13:42:29")?
);
assert_eq!(
naive_datetime_to_timestamp(&naive_datetime_whole_secs),
parse_timestamp("2020-09-08 13:42:29")?
);
Ok(())
}
#[test]
fn string_to_timestamp_invalid() {
// Test parsing invalid formats
// It would be nice to make these messages better
expect_timestamp_parse_error("", "Error parsing '' as timestamp");
expect_timestamp_parse_error("SS", "Error parsing 'SS' as timestamp");
expect_timestamp_parse_error(
"Wed, 18 Feb 2015 23:16:09 GMT",
"Error parsing 'Wed, 18 Feb 2015 23:16:09 GMT' as timestamp",
);
}
// Parse a timestamp to timestamp int with a useful human readable error message
fn parse_timestamp(s: &str) -> Result<i64> {
let result = string_to_timestamp_nanos(s);
if let Err(e) = &result {
eprintln!("Error parsing timestamp '{}': {:?}", s, e);
}
result
}
fn expect_timestamp_parse_error(s: &str, expected_err: &str) {
match string_to_timestamp_nanos(s) {
Ok(v) => panic!(
"Expected error '{}' while parsing '{}', but parsed {} instead",
expected_err, s, v
),
Err(e) => {
assert!(e.to_string().contains(expected_err),
"Can not find expected error '{}' while parsing '{}'. Actual error '{}'",
expected_err, s, e);
}
}
}
}