Add fn support_group_by_expr to Dialect trait (apache#896)

Author: jdye64

src/dialect/duckdb.rs

@@ -28,4 +28,8 @@ impl Dialect for DuckDbDialect {
     fn supports_filter_during_aggregation(&self) -> bool {
         true
     }
+
+    fn supports_group_by_expr(&self) -> bool {
+        true
+    }
 }

src/dialect/generic.rs

@@ -28,4 +28,8 @@ impl Dialect for GenericDialect {
             || ch == '#'
             || ch == '_'
     }
+
+    fn supports_group_by_expr(&self) -> bool {
+        true
+    }
 }

src/dialect/mod.rs

@@ -113,6 +113,10 @@ pub trait Dialect: Debug + Any {
     fn supports_within_after_array_aggregation(&self) -> bool {
         false
     }
+    /// Returns true if the dialects supports `group sets, roll up, or cube` expressions.
+    fn supports_group_by_expr(&self) -> bool {
+        false
+    }
     /// Dialect-specific prefix parser override
     fn parse_prefix(&self, _parser: &mut Parser) -> Option<Result<Expr, ParserError>> {
         // return None to fall back to the default behavior

src/dialect/postgresql.rs

@@ -42,6 +42,10 @@ impl Dialect for PostgreSqlDialect {
     fn supports_filter_during_aggregation(&self) -> bool {
         true
     }
+
+    fn supports_group_by_expr(&self) -> bool {
+        true
+    }
 }
 
 pub fn parse_comment(parser: &mut Parser) -> Result<Statement, ParserError> {

src/parser.rs

@@ -975,7 +975,7 @@ impl<'a> Parser<'a> {
     /// parse a group by expr. a group by expr can be one of group sets, roll up, cube, or simple
     /// expr.
     fn parse_group_by_expr(&mut self) -> Result<Expr, ParserError> {
-        if dialect_of!(self is PostgreSqlDialect | DuckDbDialect | GenericDialect) {
+        if self.dialect.supports_group_by_expr() {
             if self.parse_keywords(&[Keyword::GROUPING, Keyword::SETS]) {
                 self.expect_token(&Token::LParen)?;
                 let result = self.parse_comma_separated(|p| p.parse_tuple(false, true))?;