Added support for SystemLog to specify COMMENT in ENGINE section

src/Interpreters/SystemLog.cpp

@@ -43,6 +43,55 @@ namespace ErrorCodes
     extern const int LOGICAL_ERROR;
 }
 
+namespace
+{
+    class StorageWithComment : public IAST
+    {
+    public:
+        ASTPtr storage;
+        ASTPtr comment;
+
+        String getID(char) const override { return "Storage with comment definition"; }
+
+        ASTPtr clone() const override {
+            throw Exception(ErrorCodes::NOT_IMPLEMENTED, "Method clone is not supported");
+        }
+
+        void formatImpl(const FormatSettings &, FormatState &, FormatStateStacked) const override
+        {
+            throw Exception(ErrorCodes::NOT_IMPLEMENTED, "Method formatImpl is not supported");
+        }
+    };
+
+    class ParserStorageWithComment : public IParserBase
+    {
+    protected:
+        const char * getName() const override { return "storage definition with comment"; }
+        bool parseImpl(Pos & pos, ASTPtr & node, Expected & expected) override
+        {
+            ParserStorage storage_p;
+            ASTPtr storage;
+
+            if (!storage_p.parse(pos, storage, expected))
+                return false;
+
+            ParserKeyword s_comment("COMMENT");
+            ParserStringLiteral string_literal_parser;
+            ASTPtr comment;
+
+            if (s_comment.ignore(pos, expected))
+                string_literal_parser.parse(pos, comment, expected);
+
+            auto storage_with_comment = std::make_shared<StorageWithComment>();
+            storage_with_comment->storage = std::move(storage);
+            storage_with_comment->comment = std::move(comment);
+
+            node = storage_with_comment;
+            return true;
+        }
+    };
+}
+
 namespace
 {
 
@@ -102,8 +151,9 @@ std::shared_ptr<TSystemLog> createSystemLog(
             engine += " TTL " + ttl;
         engine += " ORDER BY (event_date, event_time)";
     }
+
     // Validate engine definition grammatically to prevent some configuration errors
-    ParserStorage storage_parser;
+    ParserStorageWithComment storage_parser;
     parseQuery(storage_parser, engine.data(), engine.data() + engine.size(),
             "Storage to create table for " + config_prefix, 0, DBMS_DEFAULT_MAX_PARSER_DEPTH);
 
@@ -450,7 +500,6 @@ void SystemLog<LogElement>::prepareTable()
     is_prepared = true;
 }
 
-
 template <typename LogElement>
 ASTPtr SystemLog<LogElement>::getCreateTableQuery()
 {
@@ -465,11 +514,16 @@ ASTPtr SystemLog<LogElement>::getCreateTableQuery()
     new_columns_list->set(new_columns_list->columns, InterpreterCreateQuery::formatColumns(ordinary_columns, alias_columns));
     create->set(create->columns_list, new_columns_list);
 
-    ParserStorage storage_parser;
+    ParserStorageWithComment storage_parser;
-    ASTPtr storage_ast = parseQuery(
+
+    ASTPtr storage_with_comment_ast = parseQuery(
         storage_parser, storage_def.data(), storage_def.data() + storage_def.size(),
         "Storage to create table for " + LogElement::name(), 0, DBMS_DEFAULT_MAX_PARSER_DEPTH);
-    create->set(create->storage, storage_ast);
+
+    StorageWithComment & storage_with_comment = storage_with_comment_ast->as<StorageWithComment &>();
+
+    create->set(create->storage, storage_with_comment.storage);
+    create->set(create->comment, storage_with_comment.comment);
 
     /// Write additional (default) settings for MergeTree engine to make it make it possible to compare ASTs
     /// and recreate tables on settings changes.

tests/integration/test_system_logs_comment/test.py

@@ -0,0 +1,42 @@
+# pylint: disable=line-too-long
+# pylint: disable=unused-argument
+# pylint: disable=redefined-outer-name
+
+import pytest
+from helpers.cluster import ClickHouseCluster
+
+cluster = ClickHouseCluster(__file__)
+node = cluster.add_instance('node_default', stay_alive=True)
+
+@pytest.fixture(scope='module', autouse=True)
+def start_cluster():
+    try:
+        cluster.start()
+        yield cluster
+    finally:
+        cluster.shutdown()
+
+
+def test_system_logs_comment():
+    node.exec_in_container(['bash', '-c', f"""echo "
+        <clickhouse>
+            <query_log>
+                <engine>ENGINE = MergeTree
+                        PARTITION BY (event_date)
+                        ORDER BY (event_time)
+                        TTL event_date + INTERVAL 14 DAY DELETE
+                        SETTINGS ttl_only_drop_parts=1
+                        COMMENT 'test_comment'
+                </engine>
+                <partition_by remove='remove'/>
+            </query_log>
+        </clickhouse>
+        " > /etc/clickhouse-server/config.d/yyy-override-query_log.xml
+        """])
+    node.restart_clickhouse()
+
+    node.query("select 1")
+    node.query("system flush logs")
+
+    comment = node.query("SELECT comment FROM system.tables WHERE name = 'query_log'")
+    assert comment =='test_comment\n'