Unparse map to sql (#13532)

* map to sql

* fix sqllogictest for map arg len error

* match array expr concisely

datafusion/functions-nested/src/map.rs

@@ -214,9 +214,9 @@ impl ScalarUDFImpl for MapFunc {
     }
 
     fn return_type(&self, arg_types: &[DataType]) -> Result<DataType> {
-        if arg_types.len() % 2 != 0 {
+        if arg_types.len() != 2 {
             return exec_err!(
-                "map requires an even number of arguments, got {} instead",
+                "map requires exactly 2 arguments, got {} instead",
                 arg_types.len()
             );
         }

datafusion/sql/src/unparser/expr.rs

@@ -464,6 +464,7 @@ impl Unparser<'_> {
             "array_element" => self.array_element_to_sql(args),
             "named_struct" => self.named_struct_to_sql(args),
             "get_field" => self.get_field_to_sql(args),
+            "map" => self.map_to_sql(args),
             // TODO: support for the construct and access functions of the `map` type
             _ => self.scalar_function_to_sql_internal(func_name, args),
         }
@@ -567,6 +568,39 @@ impl Unparser<'_> {
         Ok(ast::Expr::CompoundIdentifier(id))
     }
 
+    fn map_to_sql(&self, args: &[Expr]) -> Result<ast::Expr> {
+        if args.len() != 2 {
+            return internal_err!("map must have exactly 2 arguments");
+        }
+
+        let ast::Expr::Array(Array { elem: keys, .. }) = self.expr_to_sql(&args[0])?
+        else {
+            return internal_err!(
+                "map expects first argument to be an array, but received: {:?}",
+                &args[0]
+            );
+        };
+
+        let ast::Expr::Array(Array { elem: values, .. }) = self.expr_to_sql(&args[1])?
+        else {
+            return internal_err!(
+                "map expects second argument to be an array, but received: {:?}",
+                &args[1]
+            );
+        };
+
+        let entries = keys
+            .into_iter()
+            .zip(values)
+            .map(|(key, value)| ast::MapEntry {
+                key: Box::new(key),
+                value: Box::new(value),
+            })
+            .collect();
+
+        Ok(ast::Expr::Map(ast::Map { entries }))
+    }
+
     pub fn sort_to_sql(&self, sort: &Sort) -> Result<ast::OrderByExpr> {
         let Sort {
             expr,
@@ -1581,6 +1615,7 @@ mod tests {
     use datafusion_functions_aggregate::count::count_udaf;
     use datafusion_functions_aggregate::expr_fn::sum;
     use datafusion_functions_nested::expr_fn::{array_element, make_array};
+    use datafusion_functions_nested::map::map;
     use datafusion_functions_window::row_number::row_number_udwf;
 
     use crate::unparser::dialect::{
@@ -1996,6 +2031,10 @@ mod tests {
                 "{a: '1', b: 2}",
             ),
             (get_field(col("a.b"), "c"), "a.b.c"),
+            (
+                map(vec![lit("a"), lit("b")], vec![lit(1), lit(2)]),
+                "MAP {'a': 1, 'b': 2}",
+            ),
         ];
 
         for (expr, expected) in tests {

datafusion/sql/tests/cases/plan_to_sql.rs

@@ -27,6 +27,7 @@ use datafusion_expr::{col, lit, table_scan, wildcard, LogicalPlanBuilder};
 use datafusion_functions::unicode;
 use datafusion_functions_aggregate::grouping::grouping_udaf;
 use datafusion_functions_nested::make_array::make_array_udf;
+use datafusion_functions_nested::map::map_udf;
 use datafusion_functions_window::rank::rank_udwf;
 use datafusion_sql::planner::{ContextProvider, PlannerContext, SqlToRel};
 use datafusion_sql::unparser::dialect::{
@@ -190,7 +191,8 @@ fn roundtrip_statement() -> Result<()> {
             "SELECT [1, 2, 3][1]",
             "SELECT left[1] FROM array",
             "SELECT {a:1, b:2}",
-            "SELECT s.a FROM (SELECT {a:1, b:2} AS s)"
+            "SELECT s.a FROM (SELECT {a:1, b:2} AS s)",
+            "SELECT MAP {'a': 1, 'b': 2}"
     ];
 
     // For each test sql string, we transform as follows:
@@ -206,6 +208,7 @@ fn roundtrip_statement() -> Result<()> {
         let state = MockSessionState::default()
             .with_scalar_function(make_array_udf())
             .with_scalar_function(array_element_udf())
+            .with_scalar_function(map_udf())
             .with_aggregate_function(sum_udaf())
             .with_aggregate_function(count_udaf())
             .with_aggregate_function(max_udaf())

datafusion/sqllogictest/test_files/map.slt

@@ -185,7 +185,7 @@ SELECT MAP([[1,2], [3,4]], ['a', 'b']);
 query error
 SELECT MAP()
 
-query error DataFusion error: Execution error: map requires an even number of arguments, got 1 instead
+query error DataFusion error: Execution error: map requires exactly 2 arguments, got 1 instead
 SELECT MAP(['POST', 'HEAD'])
 
 query error DataFusion error: Execution error: Expected list, large_list or fixed_size_list, got Null