From d6ec90fb177daf93f6ada5e5e53c0f7dd9137b10 Mon Sep 17 00:00:00 2001
From: kyri-petrou <67301607+kyri-petrou@users.noreply.github.com>
Date: Fri, 23 Feb 2024 14:46:54 +1100
Subject: [PATCH] Add Mixed query execution mode (#2129)

---
 core/src/main/scala/caliban/execution/Executor.scala      | 3 +++
 .../src/main/scala/caliban/execution/QueryExecution.scala | 8 +++++++-
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/core/src/main/scala/caliban/execution/Executor.scala b/core/src/main/scala/caliban/execution/Executor.scala
index 2329f4387..73d6cf0f0 100644
--- a/core/src/main/scala/caliban/execution/Executor.scala
+++ b/core/src/main/scala/caliban/execution/Executor.scala
@@ -58,6 +58,9 @@ object Executor {
         case QueryExecution.Batched             => ZQuery.foreachBatched(in)(as)
         case QueryExecution.Parallel            => ZQuery.foreachPar(in)(as)
         case QueryExecution.Sequential          => ZQuery.foreach(in)(as)
+        case QueryExecution.Mixed               =>
+          if (isTopLevelField) ZQuery.foreachPar(in)(as)
+          else ZQuery.foreachBatched(in)(as)
       }
     }
 
diff --git a/core/src/main/scala/caliban/execution/QueryExecution.scala b/core/src/main/scala/caliban/execution/QueryExecution.scala
index 7716b4abb..d79ccc08f 100644
--- a/core/src/main/scala/caliban/execution/QueryExecution.scala
+++ b/core/src/main/scala/caliban/execution/QueryExecution.scala
@@ -19,7 +19,13 @@ object QueryExecution {
 
   /**
    * Run effectful fields sequentially but batch effects wrapped with `ZQuery.fromRequest`.
-   * This mode is recommended when most of your effects are relying on ZQuery as it avoids forking unnecessary fibers.
+   * This mode is recommended when most of your effects are backed by ZQuery DataSources as it avoids forking unnecessary fibers.
    */
   case object Batched extends QueryExecution
+
+  /**
+   * Run effectful top-level fields in [[Parallel]] mode and nested fields in [[Batched]] mode.
+   * This mode is recommended when most of your effects are backed by ZQuery DataSources but want to guarantee that top-level fields are always executed in parallel.
+   */
+  case object Mixed extends QueryExecution
 }