From 1178b77e2902e5c3612011632ca5539babac50e9 Mon Sep 17 00:00:00 2001
From: Alexander Taepper <alexander.taepper@gmail.com>
Date: Wed, 23 Sep 2026 16:40:19 +0200
Subject: [PATCH] [C++] Disable simdjson threading in chunker

---
 cpp/src/arrow/json/chunker.cc | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/cpp/src/arrow/json/chunker.cc b/cpp/src/arrow/json/chunker.cc
index f69c45b93867..c39d3ba5a6e5 100644
--- a/cpp/src/arrow/json/chunker.cc
+++ b/cpp/src/arrow/json/chunker.cc
@@ -55,7 +55,12 @@ Status ConsumeDocument(simdjson::ondemand::document_stream::iterator& it) {
 // and uses actual JSON parsing to delimit them.
 class ParsingBoundaryFinder : public BoundaryFinder {
  public:
-  explicit ParsingBoundaryFinder(MemoryPool* pool) : pool_(pool) {}
+  explicit ParsingBoundaryFinder(MemoryPool* pool) : pool_(pool) {
+    // A simdjson document stream may start a thread to index the next batch in the
+    // background. We do not want to do this eagerly as we might not need to parse
+    // the next block
+    parser_.threaded = false;
+  }
 
   Status FindFirst(std::string_view partial, std::string_view block,
                    int64_t* out_pos) override {