Enable Redshift support for specifying null treatment outside window function.

Though not explicitly mentioned in the official docs, it is valid SQL for Redshift.

Author: Roman Borschel

src/dialect/redshift.rs

@@ -156,4 +156,8 @@ impl Dialect for RedshiftSqlDialect {
     fn supports_string_literal_concatenation_with_newline(&self) -> bool {
         true
     }
+
+    fn supports_window_function_null_treatment_arg(&self) -> bool {
+        true
+    }
 }

tests/sqlparser_redshift.rs

@@ -511,3 +511,9 @@ fn test_create_table_backup() {
         "CREATE TABLE public.users_backup_test BACKUP YES DISTSTYLE AUTO AS SELECT id, name, email FROM public.users",
     );
 }
+
+#[test]
+fn test_null_treatment_inside_and_outside_window_function() {
+    redshift().verified_stmt("SELECT FIRST_VALUE(1 IGNORE NULLS) OVER () FROM (SELECT 1) t");
+    redshift().verified_stmt("SELECT FIRST_VALUE(1) IGNORE NULLS OVER () FROM (SELECT 1) t");
+}