fix(datatables): migrate fork reservations on workspace rename, and lock the parent's data tables for the whole fork

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

backend/windmill-api-workspaces/src/workspaces.rs

@@ -8039,7 +8039,6 @@ async fn point_kept_datatables_at_parent(
     forked_w_id: &str,
     cloned: &[ForkedDatatableInfo],
 ) -> Result<()> {
-    windmill_common::workspaces::lock_fork_datatables(tx, parent_w_id).await?;
     let settings: Option<serde_json::Value> = sqlx::query_scalar!(
         "SELECT datatable FROM workspace_settings WHERE workspace_id = $1",
         forked_w_id
@@ -8607,6 +8606,9 @@ async fn create_workspace_fork(
     }
 
     let mut tx: Transaction<'_, Postgres> = db.begin().await?;
+    // Before the settings clone reads the parent's data tables: a pointer this fork ends up with
+    // must not be written after cleanup of the parent decided that nothing points at its copies.
+    windmill_common::workspaces::lock_fork_datatables(&mut tx, &parent_workspace_id).await?;
 
     if nw.is_dev_workspace {
         // The checks above ran outside a transaction, so the parent's eligibility and the chain's

backend/windmill-api-workspaces/src/workspaces_extra.rs

@@ -110,6 +110,21 @@ pub(crate) async fn change_workspace_id(
     .execute(&mut *tx)
     .await?;
 
+    // A fork copy reserved for the old id would otherwise be unreachable: its creator cannot
+    // import into it or finish its fork under the new id, and nothing else would ever drop it.
+    sqlx::query(
+        r#"UPDATE global_settings SET value = jsonb_set(value, '{databases}', (
+               SELECT COALESCE(jsonb_object_agg(k, CASE WHEN v->>'workspace_id' = $1
+                   THEN jsonb_set(v, '{workspace_id}', to_jsonb($2::text)) ELSE v END), '{}'::jsonb)
+               FROM jsonb_each(COALESCE(value->'databases', '{}'::jsonb)) AS e(k, v)
+           ))
+           WHERE name = 'custom_instance_pg_databases'"#,
+    )
+    .bind(&old_id)
+    .bind(&rw.new_id)
+    .execute(&mut *tx)
+    .await?;
+
     // Duplicate workspace settings (keep copy in old workspace for reference)
     info!("Duplicating workspace_settings table");
     sqlx::query!(