From abf26d4935a831ba663554377f3ac5967ec68795 Mon Sep 17 00:00:00 2001
From: Amos Bird <amosbird@gmail.com>
Date: Wed, 24 Feb 2021 14:45:14 +0800
Subject: [PATCH] disable null_as_default when type is Nullable

---
 .../Formats/Impl/ValuesBlockInputFormat.cpp          | 12 +++++++++---
 .../0_stateless/01736_null_as_default.reference      |  2 ++
 tests/queries/0_stateless/01736_null_as_default.sql  |  5 +++++
 3 files changed, 16 insertions(+), 3 deletions(-)
 create mode 100644 tests/queries/0_stateless/01736_null_as_default.reference
 create mode 100644 tests/queries/0_stateless/01736_null_as_default.sql

diff --git a/src/Processors/Formats/Impl/ValuesBlockInputFormat.cpp b/src/Processors/Formats/Impl/ValuesBlockInputFormat.cpp
index 34a4a98f16b..7860498e4ff 100644
--- a/src/Processors/Formats/Impl/ValuesBlockInputFormat.cpp
+++ b/src/Processors/Formats/Impl/ValuesBlockInputFormat.cpp
@@ -255,9 +255,15 @@ bool ValuesBlockInputFormat::parseExpression(IColumn & column, size_t column_idx
             bool found_in_cache = false;
             const auto & result_type = header.getByPosition(column_idx).type;
             const char * delimiter = (column_idx + 1 == num_columns) ? ")" : ",";
-            auto structure = templates_cache.getFromCacheOrConstruct(result_type, format_settings.null_as_default,
-                                                                     TokenIterator(tokens), token_iterator,
-                                                                     ast, *context, &found_in_cache, delimiter);
+            auto structure = templates_cache.getFromCacheOrConstruct(
+                result_type,
+                !result_type->isNullable() && format_settings.null_as_default,
+                TokenIterator(tokens),
+                token_iterator,
+                ast,
+                *context,
+                &found_in_cache,
+                delimiter);
             templates[column_idx].emplace(structure);
             if (found_in_cache)
                 ++attempts_to_deduce_template_cached[column_idx];
diff --git a/tests/queries/0_stateless/01736_null_as_default.reference b/tests/queries/0_stateless/01736_null_as_default.reference
new file mode 100644
index 00000000000..baf83eb21d7
--- /dev/null
+++ b/tests/queries/0_stateless/01736_null_as_default.reference
@@ -0,0 +1,2 @@
+A
+\N
diff --git a/tests/queries/0_stateless/01736_null_as_default.sql b/tests/queries/0_stateless/01736_null_as_default.sql
new file mode 100644
index 00000000000..f9a4bc69acf
--- /dev/null
+++ b/tests/queries/0_stateless/01736_null_as_default.sql
@@ -0,0 +1,5 @@
+drop table if exists test_num;
+create table test_enum (c Nullable(Enum16('A' = 1, 'B' = 2))) engine Log;
+insert into test_enum values (1), (NULL);
+select * from test_enum;
+drop table if exists test_num;