From 60790d6c9299a25189bf5df77bb798e326b65d6b Mon Sep 17 00:00:00 2001
From: cangyin <excangyin@gmail.com>
Date: Fri, 30 Aug 2024 23:48:37 +0800
Subject: [PATCH] More compliant with glibc

---
 src/Common/DateLUT.cpp                                 |  8 +++++---
 tests/queries/0_stateless/03206_timezone_env.reference |  4 ++++
 tests/queries/0_stateless/03206_timezone_env.sh        | 10 ++++++++++
 3 files changed, 19 insertions(+), 3 deletions(-)
 create mode 100644 tests/queries/0_stateless/03206_timezone_env.reference
 create mode 100644 tests/queries/0_stateless/03206_timezone_env.sh

diff --git a/src/Common/DateLUT.cpp b/src/Common/DateLUT.cpp
index 55648bc587a..a0d0b95a381 100644
--- a/src/Common/DateLUT.cpp
+++ b/src/Common/DateLUT.cpp
@@ -46,12 +46,14 @@ std::string determineDefaultTimeZone()
     /// may give wrong timezone names - store the name as it is, if possible.
     std::string tz_name;
 
-    if (!tz_env_var.empty())
+    if (tz_env_var)
     {
         error_prefix = std::string("Could not determine time zone from TZ variable value: '") + tz_env_var + "': ";
 
         if (*tz_env_var == ':')
             ++tz_env_var;
+        else if (*tz_env_var == '\0')
+            tz_env_var = "UTC";
 
         tz_file_path = tz_env_var;
         tz_name = tz_env_var;
@@ -68,7 +70,7 @@ std::string determineDefaultTimeZone()
         /// Read symlink but not transitive.
         /// Example:
         ///  /etc/localtime -> /usr/share/zoneinfo//UTC
-        ///  /usr/share/zoneinfo//UTC -> UCT
+        ///  /usr/share/zoneinfo//UTC -> UTC
         /// But the preferred time zone name is pointed by the first link (UTC), and the second link is just an internal detail.
         if (FS::isSymlink(tz_file_path))
         {
@@ -89,7 +91,7 @@ std::string determineDefaultTimeZone()
             fs::path relative_path = tz_file_path.lexically_relative(tz_database_path);
 
             if (!relative_path.empty() && *relative_path.begin() != ".." && *relative_path.begin() != ".")
-                return tz_name.empty() ? relative_path.string() : tz_name;
+                return relative_path.string();
         }
 
         /// Try the same with full symlinks resolution
diff --git a/tests/queries/0_stateless/03206_timezone_env.reference b/tests/queries/0_stateless/03206_timezone_env.reference
new file mode 100644
index 00000000000..8508f8a7772
--- /dev/null
+++ b/tests/queries/0_stateless/03206_timezone_env.reference
@@ -0,0 +1,4 @@
+UTC
+Asia/Shanghai
+Asia/Shanghai
+Europe/Amsterdam
diff --git a/tests/queries/0_stateless/03206_timezone_env.sh b/tests/queries/0_stateless/03206_timezone_env.sh
new file mode 100644
index 00000000000..d1cc4bf0e35
--- /dev/null
+++ b/tests/queries/0_stateless/03206_timezone_env.sh
@@ -0,0 +1,10 @@
+#!/usr/bin/env bash
+
+CUR_DIR=$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)
+# shellcheck source=../shell_config.sh
+. "$CUR_DIR"/../shell_config.sh
+
+TZ='' ${CLICKHOUSE_LOCAL} --query "SELECT timezone()";
+TZ='Asia/Shanghai' ${CLICKHOUSE_LOCAL} --query "SELECT timezone()";
+TZ=':Asia/Shanghai' ${CLICKHOUSE_LOCAL} --query "SELECT timezone()";
+TZ=':/usr/share/zoneinfo/Europe/Amsterdam' ${CLICKHOUSE_LOCAL} --query "SELECT timezone()";