From 6b28d1ca0f89a483e03d12151a3f9e5cce60265c Mon Sep 17 00:00:00 2001
From: BharatDeva <278575558+BharatDeva@users.noreply.github.com>
Date: Wed, 3 Jun 2026 19:29:53 -0500
Subject: [PATCH] Clarify DateTime32 precision errors

---
 src/DataTypes/registerDataTypeDateTime.cpp       |  5 +++++
 .../tests/gtest_data_types_binary_encoding.cpp   | 16 ++++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/src/DataTypes/registerDataTypeDateTime.cpp b/src/DataTypes/registerDataTypeDateTime.cpp
index 58ddec112cc..8ba3ca5b0d6 100644
--- a/src/DataTypes/registerDataTypeDateTime.cpp
+++ b/src/DataTypes/registerDataTypeDateTime.cpp
@@ -86,6 +86,11 @@ static DataTypePtr create32(const ASTPtr & arguments, [[maybe_unused]] bool comp
         throw Exception(ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH,
                         "The datetime32 data type can optionally have only one argument - time zone name");
 
+    const auto * argument = arguments->children[0]->as<ASTLiteral>();
+    if (argument && argument->value.getType() == Field::Types::Which::UInt64)
+        throw Exception(ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT,
+                        "The datetime32 data type does not support precision. Use datetime64 for fractional seconds");
+
     const auto timezone = getArgument<String, ArgumentKind::Mandatory>(arguments, 0, "timezone", "datetime32");
 
     return std::make_shared<DataTypeDateTime>(timezone);
diff --git a/src/DataTypes/tests/gtest_data_types_binary_encoding.cpp b/src/DataTypes/tests/gtest_data_types_binary_encoding.cpp
index 85d110762c7..19c8871b95c 100644
--- a/src/DataTypes/tests/gtest_data_types_binary_encoding.cpp
+++ b/src/DataTypes/tests/gtest_data_types_binary_encoding.cpp
@@ -1,5 +1,6 @@
 #include <gtest/gtest.h>
 #include <Core/Field.h>
+#include <Common/Exception.h>
 #include <DataTypes/DataTypesBinaryEncoding.h>
 #include <DataTypes/DataTypeDateTime64.h>
 #include <DataTypes/DataTypeFixedString.h>
@@ -27,6 +28,7 @@ using namespace DB;
 namespace DB::ErrorCodes
 {
 extern const int UNSUPPORTED_METHOD;
+extern const int ILLEGAL_TYPE_OF_ARGUMENT;
 }
 
 
@@ -135,3 +137,17 @@ GTEST_TEST(DataTypesBinaryEncoding, EncodeAndDecode)
     check(DataTypeFactory::instance().get("json(max_dynamic_paths=10)"));
     check(DataTypeFactory::instance().get("json(max_dynamic_paths=10, max_dynamic_types=10, a.b.c uint32, SKIP a.c, b.g string, SKIP l.d.f)"));
 }
+
+GTEST_TEST(DataTypeFactory, DateTime32PrecisionError)
+{
+    try
+    {
+        DataTypeFactory::instance().get("datetime32(3)");
+        FAIL() << "Expected datetime32 precision to throw";
+    }
+    catch (const Exception & e)
+    {
+        EXPECT_EQ(e.code(), ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
+        EXPECT_NE(std::string(e.what()).find("datetime32 data type does not support precision"), std::string::npos);
+    }
+}