feat: expose relation_id and relation_attribution_no on PgColumn (#3492)

* expose relation_id and relation_attribution_no on PgColumn

* Update sqlx-postgres/src/message/row_description.rs

Co-authored-by: Austin Bonander <[email protected]>

* Update sqlx-postgres/src/column.rs

Co-authored-by: Austin Bonander <[email protected]>

* Update sqlx-postgres/src/message/row_description.rs

Co-authored-by: Austin Bonander <[email protected]>

* Update sqlx-postgres/src/column.rs

Co-authored-by: Austin Bonander <[email protected]>

* Update sqlx-postgres/src/message/row_description.rs

Co-authored-by: Austin Bonander <[email protected]>

* fix

---------

Co-authored-by: Austin Bonander <[email protected]>

sqlx-postgres/src/column.rs

@@ -10,11 +10,33 @@ pub struct PgColumn {
     pub(crate) name: UStr,
     pub(crate) type_info: PgTypeInfo,
     #[cfg_attr(feature = "offline", serde(skip))]
-    pub(crate) relation_id: Option<i32>,
+    pub(crate) relation_id: Option<crate::types::Oid>,
     #[cfg_attr(feature = "offline", serde(skip))]
     pub(crate) relation_attribute_no: Option<i16>,
 }
 
+impl PgColumn {
+    /// Returns the OID of the table this column is from, if applicable.
+    ///
+    /// This will be `None` if the column is the result of an expression.
+    ///
+    /// Corresponds to column `attrelid` of the `pg_catalog.pg_attribute` table:
+    /// <https://www.postgresql.org/docs/current/catalog-pg-attribute.html>
+    pub fn relation_id(&self) -> Option<crate::types::Oid> {
+        self.relation_id
+    }
+
+    /// Returns the 1-based index of this column in its parent table, if applicable.
+    ///
+    /// This will be `None` if the column is the result of an expression.
+    ///
+    /// Corresponds to column `attnum` of the `pg_catalog.pg_attribute` table:
+    /// <https://www.postgresql.org/docs/current/catalog-pg-attribute.html>
+    pub fn relation_attribute_no(&self) -> Option<i16> {
+        self.relation_attribute_no
+    }
+}
+
 impl Column for PgColumn {
     type Database = Postgres;
 

sqlx-postgres/src/message/row_description.rs

@@ -17,7 +17,7 @@ pub struct Field {
 
     /// If the field can be identified as a column of a specific table, the
     /// object ID of the table; otherwise zero.
-    pub relation_id: Option<i32>,
+    pub relation_id: Option<Oid>,
 
     /// If the field can be identified as a column of a specific table, the attribute number of
     /// the column; otherwise zero.
@@ -65,7 +65,7 @@ impl BackendMessage for RowDescription {
                 ));
             }
 
-            let relation_id = buf.get_i32();
+            let relation_id = buf.get_u32();
             let relation_attribute_no = buf.get_i16();
             let data_type_id = Oid(buf.get_u32());
             let data_type_size = buf.get_i16();
@@ -77,7 +77,7 @@ impl BackendMessage for RowDescription {
                 relation_id: if relation_id == 0 {
                     None
                 } else {
-                    Some(relation_id)
+                    Some(Oid(relation_id))
                 },
                 relation_attribute_no: if relation_attribute_no == 0 {
                     None