allow DateTimeField::Custom with EXTRACT in Postgres

src/dialect/generic.rs

@@ -78,4 +78,12 @@ impl Dialect for GenericDialect {
     fn support_map_literal_syntax(&self) -> bool {
         true
     }
+
+    fn allow_extract_custom(&self) -> bool {
+        true
+    }
+
+    fn allow_extract_single_quotes(&self) -> bool {
+        true
+    }
 }

src/dialect/mod.rs

@@ -499,6 +499,16 @@ pub trait Dialect: Debug + Any {
     fn describe_requires_table_keyword(&self) -> bool {
         false
     }
+
+    /// Returns true if this dialect allows the `EXTRACT` function to words other than [`Keyword`].
+    fn allow_extract_custom(&self) -> bool {
+        false
+    }
+
+    /// Returns true if this dialect allows the `EXTRACT` function to use single quotes in the part being extracted.
+    fn allow_extract_single_quotes(&self) -> bool {
+        false
+    }
 }
 
 /// This represents the operators for which precedence must be defined

src/dialect/postgresql.rs

@@ -154,6 +154,14 @@ impl Dialect for PostgreSqlDialect {
             Precedence::Or => OR_PREC,
         }
     }
+
+    fn allow_extract_custom(&self) -> bool {
+        true
+    }
+
+    fn allow_extract_single_quotes(&self) -> bool {
+        true
+    }
 }
 
 pub fn parse_comment(parser: &mut Parser) -> Result<Statement, ParserError> {

src/dialect/snowflake.rs

@@ -158,6 +158,14 @@ impl Dialect for SnowflakeDialect {
     fn describe_requires_table_keyword(&self) -> bool {
         true
     }
+
+    fn allow_extract_custom(&self) -> bool {
+        true
+    }
+
+    fn allow_extract_single_quotes(&self) -> bool {
+        true
+    }
 }
 
 /// Parse snowflake create table statement.

src/parser/mod.rs

@@ -1970,15 +1970,14 @@ impl<'a> Parser<'a> {
                 Keyword::TIMEZONE_HOUR => Ok(DateTimeField::TimezoneHour),
                 Keyword::TIMEZONE_MINUTE => Ok(DateTimeField::TimezoneMinute),
                 Keyword::TIMEZONE_REGION => Ok(DateTimeField::TimezoneRegion),
-                _ if dialect_of!(self is SnowflakeDialect | GenericDialect) => {
+                _ if self.dialect.allow_extract_custom() => {
                     self.prev_token();
                     let custom = self.parse_identifier(false)?;
                     Ok(DateTimeField::Custom(custom))
                 }
                 _ => self.expected("date/time field", next_token),
             },
-            Token::SingleQuotedString(_) if dialect_of!(self is SnowflakeDialect | GenericDialect) =>
-            {
+            Token::SingleQuotedString(_) if self.dialect.allow_extract_single_quotes() => {
                 self.prev_token();
                 let custom = self.parse_identifier(false)?;
                 Ok(DateTimeField::Custom(custom))

tests/sqlparser_common.rs

@@ -2474,7 +2474,7 @@ fn parse_extract() {
     verified_stmt("SELECT EXTRACT(TIMEZONE_REGION FROM d)");
     verified_stmt("SELECT EXTRACT(TIME FROM d)");
 
-    let dialects = all_dialects_except(|d| d.is::<SnowflakeDialect>() || d.is::<GenericDialect>());
+    let dialects = all_dialects_except(|d| d.allow_extract_custom());
     let res = dialects.parse_sql_statements("SELECT EXTRACT(JIFFY FROM d)");
     assert_eq!(
         ParserError::ParserError("Expected: date/time field, found: JIFFY".to_string()),
@@ -2573,7 +2573,7 @@ fn parse_ceil_datetime() {
     verified_stmt("SELECT CEIL(d TO SECOND) FROM df");
     verified_stmt("SELECT CEIL(d TO MILLISECOND) FROM df");
 
-    let dialects = all_dialects_except(|d| d.is::<SnowflakeDialect>() || d.is::<GenericDialect>());
+    let dialects = all_dialects_except(|d| d.allow_extract_custom());
     let res = dialects.parse_sql_statements("SELECT CEIL(d TO JIFFY) FROM df");
     assert_eq!(
         ParserError::ParserError("Expected: date/time field, found: JIFFY".to_string()),
@@ -2600,7 +2600,7 @@ fn parse_floor_datetime() {
     verified_stmt("SELECT FLOOR(d TO SECOND) FROM df");
     verified_stmt("SELECT FLOOR(d TO MILLISECOND) FROM df");
 
-    let dialects = all_dialects_except(|d| d.is::<SnowflakeDialect>() || d.is::<GenericDialect>());
+    let dialects = all_dialects_except(|d| d.allow_extract_custom());
     let res = dialects.parse_sql_statements("SELECT FLOOR(d TO JIFFY) FROM df");
     assert_eq!(
         ParserError::ParserError("Expected: date/time field, found: JIFFY".to_string()),
@@ -10467,3 +10467,75 @@ fn test_group_by_nothing() {
         );
     }
 }
+
+#[test]
+fn test_extract_seconds_ok() {
+    let dialects = all_dialects_where(|d| d.allow_extract_custom());
+    let stmt = dialects.verified_expr("EXTRACT(seconds FROM '2 seconds'::INTERVAL)");
+
+    assert_eq!(
+        stmt,
+        Expr::Extract {
+            field: DateTimeField::Custom(Ident {
+                value: "seconds".to_string(),
+                quote_style: None,
+            }),
+            syntax: ExtractSyntax::From,
+            expr: Box::new(Expr::Cast {
+                kind: CastKind::DoubleColon,
+                expr: Box::new(Expr::Value(Value::SingleQuotedString(
+                    "2 seconds".to_string()
+                ))),
+                data_type: DataType::Interval,
+                format: None,
+            }),
+        }
+    )
+}
+
+#[test]
+fn test_extract_seconds_single_quote_ok() {
+    let dialects = all_dialects_where(|d| d.allow_extract_custom());
+    let stmt = dialects.verified_expr(r#"EXTRACT('seconds' FROM '2 seconds'::INTERVAL)"#);
+
+    assert_eq!(
+        stmt,
+        Expr::Extract {
+            field: DateTimeField::Custom(Ident {
+                value: "seconds".to_string(),
+                quote_style: Some('\''),
+            }),
+            syntax: ExtractSyntax::From,
+            expr: Box::new(Expr::Cast {
+                kind: CastKind::DoubleColon,
+                expr: Box::new(Expr::Value(Value::SingleQuotedString(
+                    "2 seconds".to_string()
+                ))),
+                data_type: DataType::Interval,
+                format: None,
+            }),
+        }
+    )
+}
+
+#[test]
+fn test_extract_seconds_err() {
+    let sql = "SELECT EXTRACT(seconds FROM '2 seconds'::INTERVAL)";
+    let dialects = all_dialects_except(|d| d.allow_extract_custom());
+    let err = dialects.parse_sql_statements(sql).unwrap_err();
+    assert_eq!(
+        err.to_string(),
+        "sql parser error: Expected: date/time field, found: seconds"
+    );
+}
+
+#[test]
+fn test_extract_seconds_single_quote_err() {
+    let sql = r#"SELECT EXTRACT('seconds' FROM '2 seconds'::INTERVAL)"#;
+    let dialects = all_dialects_except(|d| d.allow_extract_single_quotes());
+    let err = dialects.parse_sql_statements(sql).unwrap_err();
+    assert_eq!(
+        err.to_string(),
+        "sql parser error: Expected: date/time field, found: 'seconds'"
+    );
+}