Expose type modifier in Column struct

tokio-postgres/src/prepare.rs

@@ -99,6 +99,7 @@ pub async fn prepare(
                 name: field.name().to_string(),
                 table_oid: Some(field.table_oid()).filter(|n| *n != 0),
                 column_id: Some(field.column_id()).filter(|n| *n != 0),
+                type_modifier: field.type_modifier(),
                 r#type: type_,
             };
             columns.push(column);

tokio-postgres/src/statement.rs

@@ -67,6 +67,7 @@ pub struct Column {
     pub(crate) name: String,
     pub(crate) table_oid: Option<u32>,
     pub(crate) column_id: Option<i16>,
+    pub(crate) type_modifier: i32,
     pub(crate) r#type: Type,
 }
 
@@ -86,6 +87,11 @@ impl Column {
         self.column_id
     }
 
+    /// Return the type modifier
+    pub fn type_modifier(&self) -> i32 {
+        self.type_modifier
+    }
+
     /// Returns the type of the column.
     pub fn type_(&self) -> &Type {
         &self.r#type

tokio-postgres/tests/test/main.rs

@@ -163,6 +163,30 @@ async fn pipelined_prepare() {
     assert_eq!(statement2.columns()[0].type_(), &Type::INT8);
 }
 
+#[tokio::test]
+async fn prepare_type_modifier() {
+    let client = connect("user=postgres").await;
+
+    let statement = client
+        .prepare("SELECT $1::BIGINT, $2::VARCHAR(7), $3::VARCHAR(101)")
+        .await
+        .unwrap();
+
+    let varlena_header_length = 4;
+    assert_eq!(statement.columns()[0].type_(), &Type::INT8);
+    assert_eq!(statement.columns()[0].type_modifier(), -1);
+    assert_eq!(statement.columns()[1].type_(), &Type::VARCHAR);
+    assert_eq!(
+        statement.columns()[1].type_modifier(),
+        7 + varlena_header_length
+    );
+    assert_eq!(statement.columns()[2].type_(), &Type::VARCHAR);
+    assert_eq!(
+        statement.columns()[2].type_modifier(),
+        101 + varlena_header_length
+    );
+}
+
 #[tokio::test]
 async fn insert_select() {
     let client = connect("user=postgres").await;