tested nested merging with anchors

src/merger/mod.rs

@@ -403,6 +403,23 @@ impl Merger {
   > {
     let type_name = type_def.name.as_str();
 
+    // 🚀 Anchor Short-Circuit Optimization
+    // An anchor is STRICTLY a struct containing merely an `id` and `type`.
+    // We aggressively bypass Database SPI `SELECT` fetches because there are no primitive
+    // mutations to apply to the row. PostgreSQL inherently protects relationships via Foreign Keys downstream.
+    let is_anchor = entity_fields.len() == 2 
+      && entity_fields.contains_key("id") 
+      && entity_fields.contains_key("type");
+
+    let has_valid_id = entity_fields
+      .get("id")
+      .and_then(|v| v.as_str())
+      .map_or(false, |s| !s.is_empty());
+
+    if is_anchor && has_valid_id {
+      return Ok((entity_fields, None, None));
+    }
+
     let entity_fetched = self.fetch_entity(&entity_fields, type_def)?;
 
     let system_keys = vec![

src/tests/fixtures.rs

@@ -8548,3 +8548,9 @@ fn test_merger_0_8() {
     let path = format!("{}/fixtures/merger.json", env!("CARGO_MANIFEST_DIR"));
     crate::tests::runner::run_test_case(&path, 0, 8).unwrap();
 }
+
+#[test]
+fn test_merger_0_9() {
+    let path = format!("{}/fixtures/merger.json", env!("CARGO_MANIFEST_DIR"));
+    crate::tests::runner::run_test_case(&path, 0, 9).unwrap();
+}