colinhacks · Nov 4, 2026 · Nov 4, 2026 · Nov 4, 2026 · Nov 4, 2026 · Nov 4, 2026
diff --git a/engine/facade/src/clients/tokio_postgres.rs b/engine/facade/src/clients/tokio_postgres.rs
@@ -33,7 +33,7 @@ impl AsyncAnswerer<Describe> for Answers<'_> {
                     let columns: Vec<Value> = stmt
                         .columns()
                         .iter()
-                        .map(|c| json!({ "name": c.name(), "oid": c.type_().oid(), "table": c.table_oid().unwrap_or(0), "attnum": c.column_id().map_or(0, i32::from) }))
+                        .map(|c| json!({ "name": c.name(), "oid": c.type_().oid(), "table": c.table_oid().unwrap_or(0), "attnum": c.column_id().map_or(0, i32::from), "typmod": c.type_modifier() }))
                         .collect();
                     serde_json::from_value(json!({ "params": params, "columns": columns })).map(Ok).map_err(|e| HostError(e.to_string()))
                 }

diff --git a/engine/native/src/postgres.rs b/engine/native/src/postgres.rs
@@ -141,7 +141,7 @@ impl Program for Postgres {
                         Ok(stmt) => json!({
                             "status": "described",
                             "params": stmt.params().iter().map(tokio_postgres::types::Type::oid).collect::<Vec<_>>(),
-                            "columns": stmt.columns().iter().map(|col| json!({ "name": col.name(), "oid": col.type_().oid(), "table": col.table_oid().unwrap_or(0), "attnum": col.column_id().map_or(0, i32::from) })).collect::<Vec<_>>(),
+                            "columns": stmt.columns().iter().map(|col| json!({ "name": col.name(), "oid": col.type_().oid(), "table": col.table_oid().unwrap_or(0), "attnum": col.column_id().map_or(0, i32::from), "typmod": col.type_modifier() })).collect::<Vec<_>>(),
                         }),
                         Err(e) => failure(&e),
                     }

diff --git a/engine/postgres/src/api.rs b/engine/postgres/src/api.rs
@@ -33,6 +33,10 @@ pub struct RawColumn {
     pub table: u32,
     #[serde(default)]
     pub attnum: i32,
+    /// The column's type modifier as RowDescription reports it (`varchar(20)`, `numeric(10,2)`);
+    /// -1, none, where the host sends none.
+    #[serde(default = "crate::pgtypes::no_typmod")]
+    pub typmod: i32,
 }
 
 /// Postgres, for [`reylo_engine_core::api::call`].

diff --git a/engine/postgres/src/infer.rs b/engine/postgres/src/infer.rs
@@ -3597,7 +3597,7 @@ mod tests {
     }
 
     fn col(nullable: bool, type_oid: u32) -> DescribedColumn {
-        DescribedColumn { name: "a".into(), type_oid, type_name: String::new(), nullable, nullable_items: None, values: None, document: None, non_finite: Default::default(), whole_row: false }
+        DescribedColumn { name: "a".into(), type_oid, typmod: -1, type_name: String::new(), nullable, nullable_items: None, values: None, document: None, non_finite: Default::default(), whole_row: false }
     }
 
     #[test]
@@ -4473,8 +4473,8 @@ mod tests {
         assert_eq!(p.head[1], None);
         assert_eq!(p.leaves.as_deref(), Some("SELECT u AS a0 FROM users u WHERE u.id = NULL"));
         // The probe says whether it was the row after all: a column named like the alias is not.
-        let row = DescribedColumn { name: "whole".into(), type_oid: 16500, type_name: "users".into(), nullable: true, nullable_items: None, values: None, document: None, non_finite: Default::default(), whole_row: false };
-        let column = DescribedColumn { name: "whole".into(), type_oid: oid::TEXT, type_name: "text".into(), nullable: true, nullable_items: None, values: None, document: None, non_finite: Default::default(), whole_row: false };
+        let row = DescribedColumn { name: "whole".into(), type_oid: 16500, typmod: -1, type_name: "users".into(), nullable: true, nullable_items: None, values: None, document: None, non_finite: Default::default(), whole_row: false };
+        let column = DescribedColumn { name: "whole".into(), type_oid: oid::TEXT, typmod: -1, type_name: "text".into(), nullable: true, nullable_items: None, values: None, document: None, non_finite: Default::default(), whole_row: false };
         assert!(resolve(p.head[0].as_ref().unwrap(), Some(&[row])).non_null);
         assert!(!resolve(p.head[0].as_ref().unwrap(), Some(&[column])).non_null);
         assert_eq!(pg("SELECT p FROM users u LEFT JOIN posts p ON p.user_id = u.id").head[0], None);

diff --git a/engine/postgres/src/jsonshape.rs b/engine/postgres/src/jsonshape.rs
@@ -1476,9 +1476,9 @@ impl ResolveCtx<'_> {
     /// A probe's column as a type: what the catalog says of it, with what the probe's own
     /// analysis said of an array it builds (`array[x, null]` holds a NULL element) and of the
     /// values, the document and the non-finite values a CHECK keeps it to or out of, as a result
-    /// column gets them.
+    /// column gets them, under the type modifier its describe reported (`varchar(20)`'s size).
     fn column(&self, col: &DescribedColumn) -> Type {
-        let ty = if col.whole_row { self.registry.render_row(col.type_oid) } else { self.registry.render(col.type_oid) };
+        let ty = if col.whole_row { self.registry.render_row(col.type_oid) } else { self.registry.render_typmod(col.type_oid, col.typmod) };
         col.non_finite.apply(crate::postgres::with_document(crate::postgres::with_values(crate::postgres::with_items(ty, col.nullable_items), col.values.as_deref(), self.registry.is_string(col.type_oid)), col.document.as_ref()))
     }
 
@@ -2390,7 +2390,7 @@ mod tests {
     const BYTEA: u32 = 17;
 
     fn column(name: &str, type_oid: u32, type_name: &str, nullable: bool) -> DescribedColumn {
-        DescribedColumn { name: name.into(), type_oid, type_name: type_name.into(), nullable, nullable_items: None, values: None, document: None, non_finite: Default::default(), whole_row: false }
+        DescribedColumn { name: name.into(), type_oid, typmod: -1, type_name: type_name.into(), nullable, nullable_items: None, values: None, document: None, non_finite: Default::default(), whole_row: false }
     }
 
     #[test]