Redshift: Support APPROXIMATE PERCENTILE_DISC

src/dialect/mod.rs

@@ -598,6 +598,11 @@ pub trait Dialect: Debug + Any {
         None
     }
 
+    /// Does the dialect support the `APPROXIMATE PERCENTILE_DISC` function syntax?
+    fn supports_approximate_percentile_disc(&self) -> bool {
+        false
+    }
+
     /// Does the dialect support trailing commas around the query?
     fn supports_trailing_commas(&self) -> bool {
         false

src/dialect/redshift.rs

@@ -128,6 +128,10 @@ impl Dialect for RedshiftSqlDialect {
         true
     }
 
+    fn supports_approximate_percentile_disc(&self) -> bool {
+        true
+    }
+
     fn supports_geometric_types(&self) -> bool {
         true
     }

src/parser/mod.rs

@@ -1836,6 +1836,20 @@ impl<'a> Parser<'a> {
 
         let dialect = self.dialect;
 
+        if dialect.supports_approximate_percentile_disc()
+            && matches!(&self.peek_token_ref().token, Token::Word(word) if word.value.eq_ignore_ascii_case("approximate"))
+            && matches!(&self.peek_nth_token_ref(1).token, Token::Word(word) if word.value.eq_ignore_ascii_case("percentile_disc"))
+        {
+            self.next_token();
+            let function_name = self.parse_object_name(false)?;
+            return self
+                .parse_function(function_name)
+                .map(|function| Expr::Prefixed {
+                    prefix: "APPROXIMATE".into(),
+                    value: Box::new(function),
+                });
+        }
+
         self.advance_token();
         let next_token_index = self.get_current_index();
         let next_token = self.get_current_token();

tests/sqlparser_redshift.rs

@@ -557,3 +557,10 @@ fn parse_unpivot_expression() {
 fn test_interval_as_column_name() {
     redshift().verified_stmt("SELECT * FROM table_name WHERE interval = 78");
 }
+
+#[test]
+fn parse_approximate_percentile_disc() {
+    redshift().verified_stmt(
+        "SELECT APPROXIMATE PERCENTILE_DISC(0.5) WITHIN GROUP (ORDER BY totalprice)",
+    );
+}