fix: render race branches in explain output (#276)

Treat RACE nodes like JOIN nodes when rendering df.explain() trees,
so both left and right branches are shown instead of rendering RACE as
a leaf node.

Keep join3 extra_nodes handling scoped to JOIN nodes, since RACE is a
binary fan-out and should only render left_node and right_node.

Add e2e coverage for both the race operator and df.race(...) dry-run
explain output, plus a live race instance that verifies the losing
branch is rendered with the skipped marker.

Author: Saithej2k

src/explain.rs

@@ -618,7 +618,7 @@ fn render_children(
                 );
             }
         }
-        "JOIN" => {
+        "JOIN" | "RACE" => {
             let mut branches = Vec::new();
             if let Some(ref left_id) = node.left_node {
                 branches.push(left_id.clone());
@@ -627,13 +627,15 @@ fn render_children(
                 branches.push(right_id.clone());
             }
 
-            // Check for extra nodes in join3
-            if let Some(ref query) = node.query {
-                if let Ok(cfg) = serde_json::from_str::<serde_json::Value>(query) {
-                    if let Some(extras) = cfg["extra_nodes"].as_array() {
-                        for extra in extras {
-                            if let Some(extra_id) = extra.as_str() {
-                                branches.push(extra_id.to_string());
+            if node.node_type == "JOIN" {
+                // Check for extra nodes in join3
+                if let Some(ref query) = node.query {
+                    if let Ok(cfg) = serde_json::from_str::<serde_json::Value>(query) {
+                        if let Some(extras) = cfg["extra_nodes"].as_array() {
+                            for extra in extras {
+                                if let Some(extra_id) = extra.as_str() {
+                                    branches.push(extra_id.to_string());
+                                }
                             }
                         }
                     }

tests/e2e/sql/05_monitoring_and_explain.sql

@@ -77,6 +77,34 @@ BEGIN
     RAISE NOTICE 'Dry-run explain passed';
 END $body$;
 
+-- Test dry-run explain renders RACE branches for both operator and function forms
+DO $body$
+DECLARE
+    explain_output TEXT;
+BEGIN
+    SELECT df.explain($$ 'SELECT ''winner''' | df.sleep(30) $$) INTO explain_output;
+
+    IF explain_output NOT LIKE '%RACE%'
+        OR explain_output NOT LIKE '%branch 1:%'
+        OR explain_output NOT LIKE '%branch 2:%'
+        OR explain_output NOT LIKE '%SELECT ''winner''%'
+        OR explain_output NOT LIKE '%SLEEP 30s%' THEN
+        RAISE EXCEPTION 'TEST FAILED: operator RACE explain should show both branches, got: %', explain_output;
+    END IF;
+
+    SELECT df.explain($$ df.race('SELECT ''winner''', df.sleep(30)) $$) INTO explain_output;
+
+    IF explain_output NOT LIKE '%RACE%'
+        OR explain_output NOT LIKE '%branch 1:%'
+        OR explain_output NOT LIKE '%branch 2:%'
+        OR explain_output NOT LIKE '%SELECT ''winner''%'
+        OR explain_output NOT LIKE '%SLEEP 30s%' THEN
+        RAISE EXCEPTION 'TEST FAILED: df.race() explain should show both branches, got: %', explain_output;
+    END IF;
+
+    RAISE NOTICE 'Dry-run RACE explain passed';
+END $body$;
+
 -- Test live instance explain
 CREATE TEMP TABLE _test_state (instance_id TEXT);
 
@@ -108,6 +136,45 @@ END $$;
 
 DROP TABLE _test_state;
 
+-- Test live RACE explain shows the skipped losing branch
+CREATE TEMP TABLE _test_race_explain_state (instance_id TEXT);
+
+INSERT INTO _test_race_explain_state
+SELECT df.start(df.race('SELECT ''winner''', df.sleep(10)), 'test-race-explain');
+
+DO $$
+DECLARE
+    inst_id TEXT;
+    status TEXT;
+    explain_output TEXT;
+BEGIN
+    SELECT instance_id INTO inst_id FROM _test_race_explain_state;
+
+    SELECT df.await_instance(inst_id, 20) INTO status;
+
+    IF status != 'completed' THEN
+        RAISE EXCEPTION 'TEST FAILED: expected completed RACE instance, got %', status;
+    END IF;
+
+    SELECT df.explain(inst_id) INTO explain_output;
+
+    IF explain_output NOT LIKE '%RACE%'
+        OR explain_output NOT LIKE '%branch 1:%'
+        OR explain_output NOT LIKE '%branch 2:%'
+        OR explain_output NOT LIKE '%SELECT ''winner''%'
+        OR explain_output NOT LIKE '%SLEEP 10s%' THEN
+        RAISE EXCEPTION 'TEST FAILED: live RACE explain should show both branches, got: %', explain_output;
+    END IF;
+
+    IF explain_output NOT LIKE '%⊘%' THEN
+        RAISE EXCEPTION 'TEST FAILED: live RACE explain should show skipped marker for losing branch, got: %', explain_output;
+    END IF;
+
+    RAISE NOTICE 'TEST PASSED: live race explain';
+END $$;
+
+DROP TABLE _test_race_explain_state;
+
 -- === Test: 31_explain_plain_sql ===
 
 DO $body$