From 56e9dadce4d268e767a72ec44efd0f830a7ffd65 Mon Sep 17 00:00:00 2001
From: Vlv <190944823+xiaobai0529@users.noreply.github.com>
Date: Wed, 21 Oct 2026 19:25:17 +0800
Subject: [PATCH] fix(substrait): validate decimal precision before
 constructing type

---
 cpp/src/arrow/engine/substrait/serde_test.cc    | 17 +++++++++++++++++
 cpp/src/arrow/engine/substrait/type_internal.cc |  4 +++-
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/cpp/src/arrow/engine/substrait/serde_test.cc b/cpp/src/arrow/engine/substrait/serde_test.cc
index 311876379830..04367d4c20f5 100644
--- a/cpp/src/arrow/engine/substrait/serde_test.cc
+++ b/cpp/src/arrow/engine/substrait/serde_test.cc
@@ -71,6 +71,7 @@
 #include "arrow/type.h"
 #include "arrow/type_fwd.h"
 #include "arrow/util/async_generator_fwd.h"
+#include "arrow/util/base64.h"
 #include "arrow/util/checked_cast.h"
 #include "arrow/util/config.h"
 #include "arrow/util/decimal.h"
@@ -1581,6 +1582,22 @@ TEST(Substrait, InvalidEmptyExtensionDeclaration) {
   ASSERT_RAISES(Invalid, DeserializePlans(*buf, [] { return kNullConsumer; }));
 }
 
+TEST(Substrait, InvalidDecimalPrecisionReturnsStatus) {
+  // GH-50230: a decimal precision outside [1, 38] must produce an error rather
+  // than aborting the process in the Decimal128Type constructor.
+  constexpr std::string_view kPocBase64 =
+      "GswBCskBCsYBEr4BCgJjMAoCYzEKAmMyCgJjMwoCYzQKAmM1CgJjNgoCYzcKAmM4CgJjOQoDYzEw"
+      "CgNjMTEKA2MxMgoDYzEzCgNjMTQKA2MxNQoDYzE2CgNjMTcSbAoCCgAKAhIACgIaAAoCKgAKAjoA"
+      "CgJSAAoCWgAKAmIACgJqAAoCcgAKA4IBAAoDigEACgfCAQQIAhAqCgWqAQIIBAoFsgECCAgKB9oB"
+      "BAoCOgAKC+IBCAoCYgASAjoACgvKAQgKAioACgJiADoDCgF0MgsQLCoHbzItc2VlZA==";
+  ASSERT_OK_AND_ASSIGN(auto poc, util::base64_decode(kPocBase64));
+  ASSERT_EQ(poc.size(), 220);
+
+  EXPECT_THAT(DeserializePlan(*Buffer::FromString(std::move(poc)),
+                              /*registry=*/nullptr, /*ext_set_out=*/nullptr),
+              Raises(StatusCode::Invalid, HasSubstr("Decimal precision out of range")));
+}
+
 TEST(Substrait, JoinPlanBasic) {
   std::string substrait_json = R"({
   "version": { "major_number": 9999, "minor_number": 9999, "patch_number": 9999 },
diff --git a/cpp/src/arrow/engine/substrait/type_internal.cc b/cpp/src/arrow/engine/substrait/type_internal.cc
index 3e8c0dda765b..3abc1ac18bee 100644
--- a/cpp/src/arrow/engine/substrait/type_internal.cc
+++ b/cpp/src/arrow/engine/substrait/type_internal.cc
@@ -171,7 +171,9 @@ Result<std::pair<std::shared_ptr<DataType>, bool>> FromProto(
 
     case substrait::Type::kDecimal: {
       const auto& decimal = type.decimal();
-      return FromProtoImpl<Decimal128Type>(decimal, decimal.precision(), decimal.scale());
+      ARROW_ASSIGN_OR_RAISE(auto decimal_type,
+                            Decimal128Type::Make(decimal.precision(), decimal.scale()));
+      return std::make_pair(std::move(decimal_type), IsNullable(decimal));
     }
 
     case substrait::Type::kStruct: {