sql: render PostgreSQL array literals as ARRAY[...] in unparser

datafusion/sql/src/unparser/dialect.rs

@@ -51,6 +51,11 @@ pub trait Dialect: Send + Sync {
     /// Return the character used to quote identifiers.
     fn identifier_quote_style(&self, _identifier: &str) -> Option<char>;
 
+    /// Whether array literals should be rendered with the `ARRAY[...]` keyword.
+    fn array_keyword(&self) -> bool {
+        false
+    }
+
     /// Does the dialect support specifying `NULLS FIRST/LAST` in `ORDER BY` clauses?
     fn supports_nulls_first_in_sort(&self) -> bool {
         true
@@ -321,6 +326,10 @@ impl Dialect for DefaultDialect {
 pub struct PostgreSqlDialect {}
 
 impl Dialect for PostgreSqlDialect {
+    fn array_keyword(&self) -> bool {
+        true
+    }
+
     fn supports_qualify(&self) -> bool {
         false
     }

datafusion/sql/src/unparser/expr.rs

@@ -604,7 +604,7 @@ impl Unparser<'_> {
             .collect::<Result<Vec<_>>>()?;
         Ok(ast::Expr::Array(Array {
             elem: args,
-            named: false,
+            named: self.dialect.array_keyword(),
         }))
     }
 
@@ -615,7 +615,10 @@ impl Unparser<'_> {
             elem.push(self.scalar_to_sql(&value)?);
         }
 
-        Ok(ast::Expr::Array(Array { elem, named: false }))
+        Ok(ast::Expr::Array(Array {
+            elem,
+            named: self.dialect.array_keyword(),
+        }))
     }
 
     fn array_element_to_sql(&self, args: &[Expr]) -> Result<ast::Expr> {

datafusion/sql/tests/cases/plan_to_sql.rs

@@ -2728,6 +2728,17 @@ fn test_unparse_window() -> Result<()> {
     Ok(())
 }
 
+#[test]
+fn test_array_to_sql_postgres() -> Result<(), DataFusionError> {
+    roundtrip_statement_with_dialect_helper!(
+        sql: "SELECT [1, 2, 3, 4, 5]",
+        parser_dialect: GenericDialect {},
+        unparser_dialect: UnparserPostgreSqlDialect {},
+        expected: @"SELECT ARRAY[1, 2, 3, 4, 5]",
+    );
+    Ok(())
+}
+
 #[test]
 fn test_like_filter() {
     let statement = generate_round_trip_statement(