Postgres: Support INTERVAL data type options

[Postgres] allows extra options for the `INTERVAL` data type; namely
fields and subsecond precision. For example `'3 years 1
second'::interval year to month` casts the interval and strips the
seconds, and `'1.3333 seconds'::interval(1)` returns `1.3` seconds.

This is supported by adding two optional fields to `DataType::Interval`,
along with a new `enum` for the allowed fields.

Note that MSSQL also supports similar options, but with more complicated
precision syntax, e.g. `INTERVAL HOUR(p) TO SECOND(q)`. This is not
implemented in this commit because I don't have a way to test it.

[Postgres]: https://www.postgresql.org/docs/17/datatype-datetime.html
[MSSQL]: https://learn.microsoft.com/en-us/sql/odbc/reference/appendixes/sql-data-types?view=sql-server-ver17

Author: mvzink

src/ast/data_type.rs

@@ -346,7 +346,11 @@ pub enum DataType {
     /// [1]: https://docs.databricks.com/aws/en/sql/language-manual/data-types/timestamp-ntz-type
     TimestampNtz,
     /// Interval type.
-    Interval,
+    ///
+    /// Optional [Postgres] field list and precision: `interval [ fields ] [ (p) ]`
+    ///
+    /// [Postgres]: https://www.postgresql.org/docs/17/datatype-datetime.html
+    Interval(Option<IntervalFields>, Option<u64>),
     /// JSON type.
     JSON,
     /// Binary JSON type.
@@ -635,7 +639,16 @@ impl fmt::Display for DataType {
                     timezone,
                 )
             }
-            DataType::Interval => write!(f, "INTERVAL"),
+            DataType::Interval(fields, precision) => {
+                write!(f, "INTERVAL")?;
+                if let Some(fields) = fields {
+                    write!(f, " {fields}")?;
+                }
+                if let Some(precision) = precision {
+                    write!(f, "({precision})")?;
+                }
+                Ok(())
+            }
             DataType::JSON => write!(f, "JSON"),
             DataType::JSONB => write!(f, "JSONB"),
             DataType::Regclass => write!(f, "REGCLASS"),
@@ -889,6 +902,48 @@ impl fmt::Display for TimezoneInfo {
     }
 }
 
+/// Fields for [Postgres] `INTERVAL` type.
+///
+/// [Postgres]: https://www.postgresql.org/docs/17/datatype-datetime.html
+#[derive(Debug, Copy, Clone, PartialEq, PartialOrd, Eq, Ord, Hash)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "visitor", derive(Visit, VisitMut))]
+pub enum IntervalFields {
+    Year,
+    Month,
+    Day,
+    Hour,
+    Minute,
+    Second,
+    YearToMonth,
+    DayToHour,
+    DayToMinute,
+    DayToSecond,
+    HourToMinute,
+    HourToSecond,
+    MinuteToSecond,
+}
+
+impl fmt::Display for IntervalFields {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            IntervalFields::Year => write!(f, "YEAR"),
+            IntervalFields::Month => write!(f, "MONTH"),
+            IntervalFields::Day => write!(f, "DAY"),
+            IntervalFields::Hour => write!(f, "HOUR"),
+            IntervalFields::Minute => write!(f, "MINUTE"),
+            IntervalFields::Second => write!(f, "SECOND"),
+            IntervalFields::YearToMonth => write!(f, "YEAR TO MONTH"),
+            IntervalFields::DayToHour => write!(f, "DAY TO HOUR"),
+            IntervalFields::DayToMinute => write!(f, "DAY TO MINUTE"),
+            IntervalFields::DayToSecond => write!(f, "DAY TO SECOND"),
+            IntervalFields::HourToMinute => write!(f, "HOUR TO MINUTE"),
+            IntervalFields::HourToSecond => write!(f, "HOUR TO SECOND"),
+            IntervalFields::MinuteToSecond => write!(f, "MINUTE TO SECOND"),
+        }
+    }
+}
+
 /// Additional information for `NUMERIC`, `DECIMAL`, and `DEC` data types
 /// following the 2016 [SQL Standard].
 ///

src/ast/mod.rs

@@ -52,7 +52,7 @@ use crate::{
 
 pub use self::data_type::{
     ArrayElemTypeDef, BinaryLength, CharLengthUnits, CharacterLength, DataType, EnumMember,
-    ExactNumberInfo, StructBracketKind, TimezoneInfo,
+    ExactNumberInfo, IntervalFields, StructBracketKind, TimezoneInfo,
 };
 pub use self::dcl::{
     AlterRoleOperation, ResetConfig, RoleOption, SecondaryRoles, SetConfigValue, Use,

src/dialect/generic.rs

@@ -183,4 +183,8 @@ impl Dialect for GenericDialect {
     fn supports_select_wildcard_exclude(&self) -> bool {
         true
     }
+
+    fn supports_interval_options(&self) -> bool {
+        true
+    }
 }

src/dialect/mod.rs

@@ -1136,6 +1136,13 @@ pub trait Dialect: Debug + Any {
     fn supports_notnull_operator(&self) -> bool {
         false
     }
+
+    /// Returns true if the dialect supports the `INTERVAL` data type with [Postgres]-style options.
+    ///
+    /// [Postgres]: https://www.postgresql.org/docs/17/datatype-datetime.html
+    fn supports_interval_options(&self) -> bool {
+        false
+    }
 }
 
 /// This represents the operators for which precedence must be defined

src/dialect/postgresql.rs

@@ -269,4 +269,11 @@ impl Dialect for PostgreSqlDialect {
     fn supports_notnull_operator(&self) -> bool {
         true
     }
+
+    /// [Postgres] supports optional field and precision options for `INTERVAL` data type.
+    ///
+    /// [Postgres]: https://www.postgresql.org/docs/17/datatype-datetime.html
+    fn supports_interval_options(&self) -> bool {
+        true
+    }
 }

src/parser/mod.rs

@@ -1534,7 +1534,7 @@ impl<'a> Parser<'a> {
         let loc = self.peek_token_ref().span.start;
         let opt_expr = self.maybe_parse(|parser| {
             match parser.parse_data_type()? {
-                DataType::Interval => parser.parse_interval(),
+                DataType::Interval(..) => parser.parse_interval(),
                 // PostgreSQL allows almost any identifier to be used as custom data type name,
                 // and we support that in `parse_data_type()`. But unlike Postgres we don't
                 // have a list of globally reserved keywords (since they vary across dialects),
@@ -10026,7 +10026,15 @@ impl<'a> Parser<'a> {
                 // Interval types can be followed by a complicated interval
                 // qualifier that we don't currently support. See
                 // parse_interval for a taste.
-                Keyword::INTERVAL => Ok(DataType::Interval),
+                Keyword::INTERVAL => {
+                    if self.dialect.supports_interval_options() {
+                        let fields = self.parse_optional_interval_fields()?;
+                        let precision = self.parse_optional_precision()?;
+                        Ok(DataType::Interval(fields, precision))
+                    } else {
+                        Ok(DataType::Interval(None, None))
+                    }
+                }
                 Keyword::JSON => Ok(DataType::JSON),
                 Keyword::JSONB => Ok(DataType::JSONB),
                 Keyword::REGCLASS => Ok(DataType::Regclass),
@@ -10995,6 +11003,85 @@ impl<'a> Parser<'a> {
         }
     }
 
+    pub fn parse_optional_interval_fields(
+        &mut self,
+    ) -> Result<Option<IntervalFields>, ParserError> {
+        match self.parse_one_of_keywords(&[
+            // Can be followed by `TO` option
+            Keyword::YEAR,
+            Keyword::DAY,
+            Keyword::HOUR,
+            Keyword::MINUTE,
+            // No `TO` option
+            Keyword::MONTH,
+            Keyword::SECOND,
+        ]) {
+            Some(Keyword::YEAR) => {
+                if self.peek_keyword(Keyword::TO) {
+                    self.expect_keyword(Keyword::TO)?;
+                    self.expect_keyword(Keyword::MONTH)?;
+                    Ok(Some(IntervalFields::YearToMonth))
+                } else {
+                    Ok(Some(IntervalFields::Year))
+                }
+            }
+            Some(Keyword::DAY) => {
+                if self.peek_keyword(Keyword::TO) {
+                    self.expect_keyword(Keyword::TO)?;
+                    match self.expect_one_of_keywords(&[
+                        Keyword::HOUR,
+                        Keyword::MINUTE,
+                        Keyword::SECOND,
+                    ])? {
+                        Keyword::HOUR => Ok(Some(IntervalFields::DayToHour)),
+                        Keyword::MINUTE => Ok(Some(IntervalFields::DayToMinute)),
+                        Keyword::SECOND => Ok(Some(IntervalFields::DayToSecond)),
+                        _ => {
+                            self.prev_token();
+                            self.expected("HOUR, MINUTE, or SECOND", self.peek_token())
+                        }
+                    }
+                } else {
+                    Ok(Some(IntervalFields::Day))
+                }
+            }
+            Some(Keyword::HOUR) => {
+                if self.peek_keyword(Keyword::TO) {
+                    self.expect_keyword(Keyword::TO)?;
+                    match self.expect_one_of_keywords(&[Keyword::MINUTE, Keyword::SECOND])? {
+                        Keyword::MINUTE => Ok(Some(IntervalFields::HourToMinute)),
+                        Keyword::SECOND => Ok(Some(IntervalFields::HourToSecond)),
+                        _ => {
+                            self.prev_token();
+                            self.expected("MINUTE or SECOND", self.peek_token())
+                        }
+                    }
+                } else {
+                    Ok(Some(IntervalFields::Hour))
+                }
+            }
+            Some(Keyword::MINUTE) => {
+                if self.peek_keyword(Keyword::TO) {
+                    self.expect_keyword(Keyword::TO)?;
+                    self.expect_keyword(Keyword::SECOND)?;
+                    Ok(Some(IntervalFields::MinuteToSecond))
+                } else {
+                    Ok(Some(IntervalFields::Minute))
+                }
+            }
+            Some(Keyword::MONTH) => Ok(Some(IntervalFields::Month)),
+            Some(Keyword::SECOND) => Ok(Some(IntervalFields::Second)),
+            Some(_) => {
+                self.prev_token();
+                self.expected(
+                    "YEAR, MONTH, DAY, HOUR, MINUTE, or SECOND",
+                    self.peek_token(),
+                )
+            }
+            None => Ok(None),
+        }
+    }
+
     /// Parse datetime64 [1]
     /// Syntax
     /// ```sql

tests/sqlparser_bigquery.rs

@@ -961,7 +961,7 @@ fn parse_typed_struct_syntax_bigquery() {
             })],
             fields: vec![StructField {
                 field_name: None,
-                field_type: DataType::Interval,
+                field_type: DataType::Interval(None, None),
                 options: None,
             }]
         },
@@ -1300,7 +1300,7 @@ fn parse_typed_struct_syntax_bigquery_and_generic() {
             })],
             fields: vec![StructField {
                 field_name: None,
-                field_type: DataType::Interval,
+                field_type: DataType::Interval(None, None),
                 options: None,
             }]
         },

tests/sqlparser_common.rs

@@ -12841,7 +12841,7 @@ fn test_extract_seconds_ok() {
                 expr: Box::new(Expr::Value(
                     (Value::SingleQuotedString("2 seconds".to_string())).with_empty_span()
                 )),
-                data_type: DataType::Interval,
+                data_type: DataType::Interval(None, None),
                 format: None,
             }),
         }
@@ -12866,7 +12866,7 @@ fn test_extract_seconds_ok() {
                     expr: Box::new(Expr::Value(
                         (Value::SingleQuotedString("2 seconds".to_string())).with_empty_span(),
                     )),
-                    data_type: DataType::Interval,
+                    data_type: DataType::Interval(None, None),
                     format: None,
                 }),
             })],
@@ -12920,7 +12920,7 @@ fn test_extract_seconds_single_quote_ok() {
                 expr: Box::new(Expr::Value(
                     (Value::SingleQuotedString("2 seconds".to_string())).with_empty_span()
                 )),
-                data_type: DataType::Interval,
+                data_type: DataType::Interval(None, None),
                 format: None,
             }),
         }

tests/sqlparser_postgres.rs

@@ -5332,6 +5332,44 @@ fn parse_at_time_zone() {
     );
 }
 
+#[test]
+fn parse_interval_data_type() {
+    pg_and_generic().verified_stmt("CREATE TABLE t (i INTERVAL)");
+    for p in 0..=6 {
+        pg_and_generic().verified_stmt(&format!("CREATE TABLE t (i INTERVAL({p}))"));
+        pg_and_generic().verified_stmt(&format!("SELECT '1 second'::INTERVAL({p})"));
+        pg_and_generic().verified_stmt(&format!("SELECT CAST('1 second' AS INTERVAL({p}))"));
+    }
+    let fields = [
+        "YEAR",
+        "MONTH",
+        "DAY",
+        "HOUR",
+        "MINUTE",
+        "SECOND",
+        "YEAR TO MONTH",
+        "DAY TO HOUR",
+        "DAY TO MINUTE",
+        "DAY TO SECOND",
+        "HOUR TO MINUTE",
+        "HOUR TO SECOND",
+        "MINUTE TO SECOND",
+    ];
+    for field in fields {
+        pg_and_generic().verified_stmt(&format!("CREATE TABLE t (i INTERVAL {field})"));
+        pg_and_generic().verified_stmt(&format!("SELECT '1 second'::INTERVAL {field}"));
+        pg_and_generic().verified_stmt(&format!("SELECT CAST('1 second' AS INTERVAL {field})"));
+    }
+    for p in 0..=6 {
+        for field in fields {
+            pg_and_generic().verified_stmt(&format!("CREATE TABLE t (i INTERVAL {field}({p}))"));
+            pg_and_generic().verified_stmt(&format!("SELECT '1 second'::INTERVAL {field}({p})"));
+            pg_and_generic()
+                .verified_stmt(&format!("SELECT CAST('1 second' AS INTERVAL {field}({p}))"));
+        }
+    }
+}
+
 #[test]
 fn parse_create_table_with_options() {
     let sql = "CREATE TABLE t (c INT) WITH (foo = 'bar', a = 123)";