From bf3a3ad607bf1059fc1839fc1ff5c2806dac1b86 Mon Sep 17 00:00:00 2001
From: Yakov Olkhovskiy <yakov@clickhouse.com>
Date: Tue, 8 Oct 2024 02:27:36 +0000
Subject: [PATCH 1/2] fix ephemeral comment

---
 src/Parsers/ParserCreateQuery.h | 24 +++++++++++++++---------
 1 file changed, 15 insertions(+), 9 deletions(-)

diff --git a/src/Parsers/ParserCreateQuery.h b/src/Parsers/ParserCreateQuery.h
index 82da2e7ea0b..a58e190ecd9 100644
--- a/src/Parsers/ParserCreateQuery.h
+++ b/src/Parsers/ParserCreateQuery.h
@@ -237,6 +237,7 @@ bool IParserColumnDeclaration<NameParser>::parseImpl(Pos & pos, ASTPtr & node, E
             null_modifier.emplace(true);
     }
 
+    bool is_comment = false;
     /// Collate is also allowed after NULL/NOT NULL
     if (!collation_expression && s_collate.ignore(pos, expected)
         && !collation_parser.parse(pos, collation_expression, expected))
@@ -254,7 +255,9 @@ bool IParserColumnDeclaration<NameParser>::parseImpl(Pos & pos, ASTPtr & node, E
     else if (s_ephemeral.ignore(pos, expected))
     {
         default_specifier = s_ephemeral.getName();
-        if (!expr_parser.parse(pos, default_expression, expected) && type)
+        if (s_comment.ignore(pos, expected))
+            is_comment = true;
+        if ((is_comment || !expr_parser.parse(pos, default_expression, expected)) && type)
         {
             ephemeral_default = true;
 
@@ -289,19 +292,22 @@ bool IParserColumnDeclaration<NameParser>::parseImpl(Pos & pos, ASTPtr & node, E
     if (require_type && !type && !default_expression)
         return false; /// reject column name without type
 
-    if ((type || default_expression) && allow_null_modifiers && !null_modifier.has_value())
+    if (!is_comment)
     {
-        if (s_not.ignore(pos, expected))
+        if ((type || default_expression) && allow_null_modifiers && !null_modifier.has_value())
         {
-            if (!s_null.ignore(pos, expected))
-                return false;
-            null_modifier.emplace(false);
+            if (s_not.ignore(pos, expected))
+            {
+                if (!s_null.ignore(pos, expected))
+                    return false;
+                null_modifier.emplace(false);
+            }
+            else if (s_null.ignore(pos, expected))
+                null_modifier.emplace(true);
         }
-        else if (s_null.ignore(pos, expected))
-            null_modifier.emplace(true);
     }
 
-    if (s_comment.ignore(pos, expected))
+    if (is_comment || s_comment.ignore(pos, expected))
     {
         /// should be followed by a string literal
         if (!string_literal_parser.parse(pos, comment_expression, expected))

From 3827d90bb0e896320d8281073a266a75fa6773ce Mon Sep 17 00:00:00 2001
From: Yakov Olkhovskiy <yakov@clickhouse.com>
Date: Tue, 8 Oct 2024 02:37:41 +0000
Subject: [PATCH 2/2] add test

---
 .../0_stateless/03250_ephemeral_comment.reference     |  0
 tests/queries/0_stateless/03250_ephemeral_comment.sql | 11 +++++++++++
 2 files changed, 11 insertions(+)
 create mode 100644 tests/queries/0_stateless/03250_ephemeral_comment.reference
 create mode 100644 tests/queries/0_stateless/03250_ephemeral_comment.sql

diff --git a/tests/queries/0_stateless/03250_ephemeral_comment.reference b/tests/queries/0_stateless/03250_ephemeral_comment.reference
new file mode 100644
index 00000000000..e69de29bb2d
diff --git a/tests/queries/0_stateless/03250_ephemeral_comment.sql b/tests/queries/0_stateless/03250_ephemeral_comment.sql
new file mode 100644
index 00000000000..906417b9c29
--- /dev/null
+++ b/tests/queries/0_stateless/03250_ephemeral_comment.sql
@@ -0,0 +1,11 @@
+drop table if exists test;
+CREATE TABLE test (
+    `start_s`  UInt32 EPHEMERAL COMMENT 'start UNIX time' ,
+    `start_us` UInt16 EPHEMERAL COMMENT 'start microseconds',
+    `finish_s`  UInt32 EPHEMERAL COMMENT 'finish UNIX time',
+    `finish_us` UInt16 EPHEMERAL COMMENT 'finish microseconds',
+    `captured` DateTime MATERIALIZED fromUnixTimestamp(start_s),
+    `duration` Decimal32(6) MATERIALIZED finish_s - start_s + (finish_us - start_us)/1000000
+)
+ENGINE Null;
+drop table if exists test;