feat: create union type for virtual tables (#269)

* add ability to create union type

* rework to use proper union functions

* check for panic

* swap for if

* tweak import

* remove workaround

* remove deref

* Remove duplicate use

src/vtab/logical_type.rs

@@ -217,6 +217,23 @@ impl LogicalType {
         }
     }
 
+    /// Make a `LogicalType` for `union`
+    pub fn union_type(fields: &[(&str, LogicalType)]) -> Self {
+        let keys: Vec<CString> = fields.iter().map(|f| CString::new(f.0).unwrap()).collect();
+        let values: Vec<duckdb_logical_type> = fields.iter().map(|it| it.1.ptr).collect();
+        let name_ptrs = keys.iter().map(|it| it.as_ptr()).collect::<Vec<*const c_char>>();
+
+        unsafe {
+            Self {
+                ptr: duckdb_create_union_type(
+                    values.as_slice().as_ptr().cast_mut(),
+                    name_ptrs.as_slice().as_ptr().cast_mut(),
+                    fields.len() as idx_t,
+                ),
+            }
+        }
+    }
+
     /// Logical type ID
     pub fn id(&self) -> LogicalTypeId {
         let duckdb_type_id = unsafe { duckdb_get_type_id(self.ptr) };
@@ -227,16 +244,22 @@ impl LogicalType {
     pub fn num_children(&self) -> usize {
         match self.id() {
             LogicalTypeId::Struct => unsafe { duckdb_struct_type_child_count(self.ptr) as usize },
+            LogicalTypeId::Union => unsafe { duckdb_union_type_member_count(self.ptr) as usize },
             LogicalTypeId::List => 1,
             _ => 0,
         }
     }
 
     /// Logical type child name by idx
+    ///
+    /// Panics if the logical type is not a struct or union
     pub fn child_name(&self, idx: usize) -> String {
-        assert_eq!(self.id(), LogicalTypeId::Struct);
         unsafe {
-            let child_name_ptr = duckdb_struct_type_child_name(self.ptr, idx as u64);
+            let child_name_ptr = match self.id() {
+                LogicalTypeId::Struct => duckdb_struct_type_child_name(self.ptr, idx as u64),
+                LogicalTypeId::Union => duckdb_union_type_member_name(self.ptr, idx as u64),
+                _ => panic!("not a struct or union"),
+            };
             let c_str = CString::from_raw(child_name_ptr);
             let name = c_str.to_str().unwrap();
             name.to_string()
@@ -245,14 +268,20 @@ impl LogicalType {
 
     /// Logical type child by idx
     pub fn child(&self, idx: usize) -> Self {
-        let c_logical_type = unsafe { duckdb_struct_type_child_type(self.ptr, idx as u64) };
+        let c_logical_type = unsafe {
+            match self.id() {
+                LogicalTypeId::Struct => duckdb_struct_type_child_type(self.ptr, idx as u64),
+                LogicalTypeId::Union => duckdb_union_type_member_type(self.ptr, idx as u64),
+                _ => panic!("not a struct or union"),
+            }
+        };
         Self::from(c_logical_type)
     }
 }
 
 #[cfg(test)]
 mod test {
-    use crate::vtab::LogicalType;
+    use super::{LogicalType, LogicalTypeId};
 
     #[test]
     fn test_struct() {
@@ -280,4 +309,21 @@ mod test {
         assert_eq!(typ.decimal_width(), 0);
         assert_eq!(typ.decimal_scale(), 0);
     }
+
+    #[test]
+    fn test_union_type() {
+        let fields = &[
+            ("hello", LogicalType::new(LogicalTypeId::Boolean)),
+            ("world", LogicalType::new(LogicalTypeId::Integer)),
+        ];
+        let typ = LogicalType::union_type(fields);
+
+        assert_eq!(typ.num_children(), 2);
+
+        assert_eq!(typ.child_name(0), "hello");
+        assert_eq!(typ.child(0).id(), LogicalTypeId::Boolean);
+
+        assert_eq!(typ.child_name(1), "world");
+        assert_eq!(typ.child(1).id(), LogicalTypeId::Integer);
+    }
 }