enhancement: support comment for create external table

src/Parsers/ParserCreateExternalTableQuery.cpp

@@ -8,6 +8,20 @@
 namespace DB
 {
 
+namespace
+{
+ASTPtr parseComment(IParser::Pos & pos, Expected & expected)
+{
+    ParserKeyword s_comment("COMMENT");
+    ParserStringLiteral string_literal_parser;
+    ASTPtr comment;
+
+    s_comment.ignore(pos, expected) && string_literal_parser.parse(pos, comment, expected);
+
+    return comment;
+}
+}
+
 bool DB::ParserCreateExternalTableQuery::parseImpl(Pos & pos, ASTPtr & node, Expected & expected, [[ maybe_unused ]] bool hint)
 {
     ParserKeyword s_create("CREATE");
@@ -52,6 +66,8 @@ bool DB::ParserCreateExternalTableQuery::parseImpl(Pos & pos, ASTPtr & node, Exp
             return false;
     }
 
+    auto comment = parseComment(pos, expected);
+
     auto create_query = std::make_shared<ASTCreateQuery>();
     node = create_query;
 
@@ -72,6 +88,9 @@ bool DB::ParserCreateExternalTableQuery::parseImpl(Pos & pos, ASTPtr & node, Exp
     if (create_query->table)
         create_query->children.push_back(create_query->table);
 
+    if (comment)
+        create_query->set(create_query->comment, comment);
+
     auto storage = std::make_shared<ASTStorage>();
     storage->set(storage->engine, makeASTFunction("ExternalTable"));
     storage->set(storage->settings, settings);

src/Storages/ExternalTable/StorageExternalTable.cpp

@@ -11,11 +11,19 @@ namespace DB
 StorageExternalTable::StorageExternalTable(
     const StorageID & table_id,
     std::unique_ptr<ExternalTableSettings>  settings,
+    const String & comment,
     bool is_attach,
     ContextPtr context_)
 : IStorage(table_id)
 , WithContext(context_)
 {
+    if (!comment.empty())
+    {
+        StorageInMemoryMetadata storage_metadata;
+        storage_metadata.setComment(comment);
+        setInMemoryMetadata(storage_metadata);
+    }
+
     external_table = ExternalTableFactory::instance().getExternalTable(table_id.getTableName(), std::move(settings));
 
     /// Two situations:
@@ -95,6 +103,7 @@ void registerStorageExternalTable(StorageFactory & factory)
         return StorageExternalTable::create(
                 args.table_id,
                 std::move(settings),
+                args.comment,
                 args.attach,
                 args.getContext()->getGlobalContext());
     };

src/Storages/ExternalTable/StorageExternalTable.h

@@ -43,6 +43,7 @@ class StorageExternalTable final : public shared_ptr_helper<StorageExternalTable
     StorageExternalTable(
         const StorageID & table_id,
         std::unique_ptr<ExternalTableSettings> settings,
+        const String & comment,
         bool is_attach,
         ContextPtr context_);