[Minor] Extract interval parsing logic, add unit tests (#2984)

* Extract interval parsing logic, add unit tests

* Update datafusion/sql/src/interval.rs

datafusion/common/src/scalar.rs

@@ -23,7 +23,8 @@ use arrow::{
     compute::kernels::cast::{cast, cast_with_options, CastOptions},
     datatypes::{
         ArrowDictionaryKeyType, ArrowNativeType, DataType, Field, Float32Type,
-        Float64Type, Int16Type, Int32Type, Int64Type, Int8Type, IntervalUnit, TimeUnit,
+        Float64Type, Int16Type, Int32Type, Int64Type, Int8Type, IntervalDayTimeType,
+        IntervalMonthDayNanoType, IntervalUnit, IntervalYearMonthType, TimeUnit,
         TimestampMicrosecondType, TimestampMillisecondType, TimestampNanosecondType,
         TimestampSecondType, UInt16Type, UInt32Type, UInt64Type, UInt8Type,
         DECIMAL_MAX_PRECISION,
@@ -618,6 +619,28 @@ impl ScalarValue {
             precision, scale
         )))
     }
+
+    /// Returns a [`ScalarValue::IntervalYearMonth`] representing
+    /// `years` years and `months` months
+    pub fn new_interval_ym(years: i32, months: i32) -> Self {
+        let val = IntervalYearMonthType::make_value(years, months);
+        ScalarValue::IntervalYearMonth(Some(val))
+    }
+
+    /// Returns a [`ScalarValue::IntervalDayTime`] representing
+    /// `days` days and `millis` milliseconds
+    pub fn new_interval_dt(days: i32, millis: i32) -> Self {
+        let val = IntervalDayTimeType::make_value(days, millis);
+        Self::IntervalDayTime(Some(val))
+    }
+
+    /// Returns a [`ScalarValue::IntervalMonthDayNano`] representing
+    /// `months` months and `days` days, and `nanos` nanoseconds
+    pub fn new_interval_mdn(months: i32, days: i32, nanos: i64) -> Self {
+        let val = IntervalMonthDayNanoType::make_value(months, days, nanos);
+        ScalarValue::IntervalMonthDayNano(Some(val))
+    }
+
     /// Getter for the `DataType` of the value
     pub fn get_datatype(&self) -> DataType {
         match self {

datafusion/sql/src/interval.rs

@@ -0,0 +1,214 @@
+// 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.
+
+//! Interval parsing logic
+use datafusion_common::{DataFusionError, Result, ScalarValue};
+use std::str::FromStr;
+
+const SECONDS_PER_HOUR: f32 = 3_600_f32;
+const MILLIS_PER_SECOND: f32 = 1_000_f32;
+
+/// Parses a string with an interval like `'0.5 MONTH'` to an
+/// appropriately typed [`ScalarValue`]
+pub(crate) fn parse_interval(leading_field: &str, value: &str) -> Result<ScalarValue> {
+    // We are storing parts as integers, it's why we need to align parts fractional
+    // INTERVAL '0.5 MONTH' = 15 days, INTERVAL '1.5 MONTH' = 1 month 15 days
+    // INTERVAL '0.5 DAY' = 12 hours, INTERVAL '1.5 DAY' = 1 day 12 hours
+    let align_interval_parts =
+        |month_part: f32, mut day_part: f32, mut milles_part: f32| -> (i32, i32, f32) {
+            // Convert fractional month to days, It's not supported by Arrow types, but anyway
+            day_part += (month_part - (month_part as i32) as f32) * 30_f32;
+
+            // Convert fractional days to hours
+            milles_part += (day_part - ((day_part as i32) as f32))
+                * 24_f32
+                * SECONDS_PER_HOUR
+                * MILLIS_PER_SECOND;
+
+            (month_part as i32, day_part as i32, milles_part)
+        };
+
+    let calculate_from_part =
+        |interval_period_str: &str, interval_type: &str| -> Result<(i32, i32, f32)> {
+            // @todo It's better to use Decimal in order to protect rounding errors
+            // Wait https://github.com/apache/arrow/pull/9232
+            let interval_period = match f32::from_str(interval_period_str) {
+                Ok(n) => n,
+                Err(_) => {
+                    return Err(DataFusionError::NotImplemented(format!(
+                        "Unsupported Interval Expression with value {:?}",
+                        value
+                    )));
+                }
+            };
+
+            if interval_period > (i32::MAX as f32) {
+                return Err(DataFusionError::NotImplemented(format!(
+                    "Interval field value out of range: {:?}",
+                    value
+                )));
+            }
+
+            match interval_type.to_lowercase().as_str() {
+                "year" => Ok(align_interval_parts(interval_period * 12_f32, 0.0, 0.0)),
+                "month" => Ok(align_interval_parts(interval_period, 0.0, 0.0)),
+                "day" | "days" => Ok(align_interval_parts(0.0, interval_period, 0.0)),
+                "hour" | "hours" => {
+                    Ok((0, 0, interval_period * SECONDS_PER_HOUR * MILLIS_PER_SECOND))
+                }
+                "minutes" | "minute" => {
+                    Ok((0, 0, interval_period * 60_f32 * MILLIS_PER_SECOND))
+                }
+                "seconds" | "second" => Ok((0, 0, interval_period * MILLIS_PER_SECOND)),
+                "milliseconds" | "millisecond" => Ok((0, 0, interval_period)),
+                _ => Err(DataFusionError::NotImplemented(format!(
+                    "Invalid input syntax for type interval: {:?}",
+                    value
+                ))),
+            }
+        };
+
+    let mut result_month: i64 = 0;
+    let mut result_days: i64 = 0;
+    let mut result_millis: i64 = 0;
+
+    let mut parts = value.split_whitespace();
+
+    loop {
+        let interval_period_str = parts.next();
+        if interval_period_str.is_none() {
+            break;
+        }
+
+        let unit = parts.next().unwrap_or(leading_field);
+
+        let (diff_month, diff_days, diff_millis) =
+            calculate_from_part(interval_period_str.unwrap(), unit)?;
+
+        result_month += diff_month as i64;
+
+        if result_month > (i32::MAX as i64) {
+            return Err(DataFusionError::NotImplemented(format!(
+                "Interval field value out of range: {:?}",
+                value
+            )));
+        }
+
+        result_days += diff_days as i64;
+
+        if result_days > (i32::MAX as i64) {
+            return Err(DataFusionError::NotImplemented(format!(
+                "Interval field value out of range: {:?}",
+                value
+            )));
+        }
+
+        result_millis += diff_millis as i64;
+
+        if result_millis > (i32::MAX as i64) {
+            return Err(DataFusionError::NotImplemented(format!(
+                "Interval field value out of range: {:?}",
+                value
+            )));
+        }
+    }
+
+    // Interval is tricky thing
+    // 1 day is not 24 hours because timezones, 1 year != 365/364! 30 days != 1 month
+    // The true way to store and calculate intervals is to store it as it defined
+    // It's why we there are 3 different interval types in Arrow
+    if result_month != 0 && (result_days != 0 || result_millis != 0) {
+        let result: i128 = ((result_month as i128) << 96)
+                | ((result_days as i128) << 64)
+                // IntervalMonthDayNano uses nanos, but IntervalDayTime uses milles
+                | ((result_millis * 1_000_000_i64) as i128);
+
+        return Ok(ScalarValue::IntervalMonthDayNano(Some(result)));
+    }
+
+    // Month interval
+    if result_month != 0 {
+        return Ok(ScalarValue::IntervalYearMonth(Some(result_month as i32)));
+    }
+
+    let result: i64 = (result_days << 32) | result_millis;
+    Ok(ScalarValue::IntervalDayTime(Some(result)))
+}
+
+#[cfg(test)]
+mod test {
+    use crate::assert_contains;
+
+    use super::*;
+
+    #[test]
+    fn test_parse_ym() {
+        assert_eq!(
+            parse_interval("months", "1 month").unwrap(),
+            ScalarValue::new_interval_ym(0, 1)
+        );
+
+        assert_eq!(
+            parse_interval("months", "2 month").unwrap(),
+            ScalarValue::new_interval_ym(0, 2)
+        );
+
+        assert_eq!(
+            parse_interval("months", "3 year 1 month").unwrap(),
+            ScalarValue::new_interval_ym(3, 1)
+        );
+
+        assert_contains!(
+            parse_interval("months", "1 years 1 month")
+                .unwrap_err()
+                .to_string(),
+            r#"Invalid input syntax for type interval: "1 years 1 month""#
+        );
+    }
+
+    #[test]
+    fn test_dt() {
+        assert_eq!(
+            parse_interval("months", "5 days").unwrap(),
+            ScalarValue::new_interval_dt(5, 0)
+        );
+
+        assert_eq!(
+            parse_interval("months", "7 days 3 hours").unwrap(),
+            ScalarValue::new_interval_dt(
+                7,
+                (3.0 * SECONDS_PER_HOUR * MILLIS_PER_SECOND) as i32
+            )
+        );
+
+        assert_eq!(
+            parse_interval("months", "7 days 5 minutes").unwrap(),
+            ScalarValue::new_interval_dt(7, (5.0 * 60.0 * MILLIS_PER_SECOND) as i32)
+        );
+    }
+
+    #[test]
+    // https://github.com/apache/arrow-rs/pull/2235
+    #[ignore]
+    fn test_mdn() {
+        // these should be the same, I think
+        assert_eq!(
+            parse_interval("months", "1 year 25 millisecond").unwrap(),
+            ScalarValue::new_interval_mdn(12, 0, 25 * 1_000_000)
+        );
+    }
+}

datafusion/sql/src/lib.rs

@@ -18,6 +18,7 @@
 //! This module provides a SQL parser that translates SQL queries into an abstract syntax
 //! tree (AST), and a SQL query planner that creates a logical plan from the AST.
 
+mod interval;
 pub mod parser;
 pub mod planner;
 mod table_reference;