Copy comment when using CREATE AS statement

src/Backups/DDLAdjustingForBackupVisitor.cpp

@@ -20,7 +20,7 @@ namespace
         /// If this is a definition of a system table we'll remove columns and comment because they're redundant for backups.
         auto & create = data.create_query->as<ASTCreateQuery &>();
         create.reset(create.columns_list);
-        create.reset(create.comment);
+        create.comment.reset();
     }
 
     void visitStorageReplicatedTableEngine(ASTStorage & storage, const DDLAdjustingForBackupVisitor::Data & data)

src/Databases/DatabaseFilesystem.cpp

@@ -192,7 +192,7 @@ ASTPtr DatabaseFilesystem::getCreateDatabaseQuery() const
     if (const auto database_comment = getDatabaseComment(); !database_comment.empty())
     {
         auto & ast_create_query = ast->as<ASTCreateQuery &>();
-        ast_create_query.set(ast_create_query.comment, std::make_shared<ASTLiteral>(database_comment));
+        ast_create_query.comment = std::make_shared<ASTLiteral>(database_comment);
     }
 
     return ast;

src/Databases/DatabaseMemory.cpp

@@ -107,7 +107,7 @@ ASTPtr DatabaseMemory::getCreateDatabaseQuery() const
     create_query->storage->set(create_query->storage->engine, engine);
 
     if (const auto comment_value = getDatabaseComment(); !comment_value.empty())
-        create_query->set(create_query->comment, std::make_shared<ASTLiteral>(comment_value));
+        create_query->comment = std::make_shared<ASTLiteral>(comment_value);
 
     return create_query;
 }

src/Databases/DatabaseOnDisk.cpp

@@ -535,7 +535,7 @@ ASTPtr DatabaseOnDisk::getCreateDatabaseQuery() const
     if (const auto database_comment = getDatabaseComment(); !database_comment.empty())
     {
         auto & ast_create_query = ast->as<ASTCreateQuery &>();
-        ast_create_query.set(ast_create_query.comment, std::make_shared<ASTLiteral>(database_comment));
+        ast_create_query.comment = std::make_shared<ASTLiteral>(database_comment);
     }
 
     return ast;
@@ -784,8 +784,7 @@ ASTPtr DatabaseOnDisk::getCreateQueryFromStorage(const String & table_name, cons
         static_cast<unsigned>(settings.max_parser_backtracks),
         throw_on_error);
 
-    create_table_query->set(create_table_query->as<ASTCreateQuery>()->comment,
+    create_table_query->as<ASTCreateQuery>()->comment = std::make_shared<ASTLiteral>("SYSTEM TABLE is built on the fly.");
-                            std::make_shared<ASTLiteral>("SYSTEM TABLE is built on the fly."));
 
     return create_table_query;
 }

src/Databases/DatabasesCommon.cpp

@@ -114,9 +114,9 @@ void applyMetadataChangesToCreateQuery(const ASTPtr & query, const StorageInMemo
     }
 
     if (metadata.comment.empty())
-        ast_create_query.reset(ast_create_query.comment);
+        ast_create_query.comment.reset();
     else
-        ast_create_query.set(ast_create_query.comment, std::make_shared<ASTLiteral>(metadata.comment));
+        ast_create_query.comment = std::make_shared<ASTLiteral>(metadata.comment);
 }
 
 

src/Interpreters/InterpreterCreateQuery.cpp

@@ -785,6 +785,9 @@ InterpreterCreateQuery::TableProperties InterpreterCreateQuery::getTableProperti
         auto as_storage_metadata = as_storage->getInMemoryMetadataPtr();
         properties.columns = as_storage_metadata->getColumns();
 
+        if (!create.comment)
+            create.comment = std::make_shared<ASTLiteral>(Field(as_storage_metadata->comment));
+
         /// Secondary indices and projections make sense only for MergeTree family of storage engines.
         /// We should not copy them for other storages.
         if (create.storage && endsWith(create.storage->engine->name, "MergeTree"))

src/Interpreters/SystemLog.cpp

@@ -656,7 +656,7 @@ ASTPtr SystemLog<LogElement>::getCreateTableQuery()
     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);
+    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.

src/Parsers/ASTCreateQuery.cpp

@@ -255,7 +255,7 @@ ASTPtr ASTCreateQuery::clone() const
     if (as_table_function)
         res->set(res->as_table_function, as_table_function->clone());
     if (comment)
-        res->set(res->comment, comment->clone());
+        res->comment = comment->clone();
 
     cloneOutputOptions(*res);
     cloneTableOptions(*res);

src/Parsers/ASTCreateQuery.h

@@ -112,7 +112,7 @@ public:
     String as_table;
     IAST * as_table_function = nullptr;
     ASTSelectWithUnionQuery * select = nullptr;
-    IAST * comment = nullptr;
+    ASTPtr comment = nullptr;
     ASTPtr sql_security = nullptr;
 
     ASTTableOverrideList * table_overrides = nullptr; /// For CREATE DATABASE with engines that automatically create tables

src/Parsers/ParserCreateQuery.cpp

@@ -861,7 +861,7 @@ bool ParserCreateTableQuery::parseImpl(Pos & pos, ASTPtr & node, Expected & expe
     query->set(query->as_table_function, as_table_function);
 
     if (comment)
-        query->set(query->comment, comment);
+        query->comment = comment;
 
     if (query->columns_list && query->columns_list->primary_key)
     {
@@ -1012,8 +1012,7 @@ bool ParserCreateLiveViewQuery::parseImpl(Pos & pos, ASTPtr & node, Expected & e
     query->set(query->select, select);
 
     if (comment)
-        query->set(query->comment, comment);
+        query->comment = comment;
-
     if (sql_security)
         query->sql_security = typeid_cast<std::shared_ptr<ASTSQLSecurity>>(sql_security);
 
@@ -1414,7 +1413,8 @@ bool ParserCreateDatabaseQuery::parseImpl(Pos & pos, ASTPtr & node, Expected & e
 
     query->set(query->storage, storage);
     if (comment)
-        query->set(query->comment, comment);
+        query->comment = comment;
+
     if (table_overrides && !table_overrides->children.empty())
         query->set(query->table_overrides, table_overrides);
 
@@ -1617,7 +1617,7 @@ bool ParserCreateViewQuery::parseImpl(Pos & pos, ASTPtr & node, Expected & expec
     if (refresh_strategy)
         query->set(query->refresh_strategy, refresh_strategy);
     if (comment)
-        query->set(query->comment, comment);
+        query->comment = comment;
     if (sql_security)
         query->sql_security = typeid_cast<std::shared_ptr<ASTSQLSecurity>>(sql_security);
 
@@ -1794,7 +1794,7 @@ bool ParserCreateDictionaryQuery::parseImpl(IParser::Pos & pos, ASTPtr & node, E
     query->cluster = cluster_str;
 
     if (comment)
-        query->set(query->comment, comment);
+        query->comment = comment;
 
     return true;
 }

tests/queries/0_stateless/03033_create_as_copies_comment.reference

@@ -0,0 +1,3 @@
+original comment
+original comment
+new comment

tests/queries/0_stateless/03033_create_as_copies_comment.sql

@@ -0,0 +1,11 @@
+DROP TABLE IF EXISTS base;
+DROP TABLE IF EXISTS copy_without_comment;
+DROP TABLE IF EXISTS copy_with_comment;
+
+CREATE TABLE base (a Int32) ENGINE = MergeTree ORDER BY a COMMENT 'original comment';
+CREATE TABLE copy_without_comment as base;
+CREATE TABLE copy_with_comment as base COMMENT 'new comment';
+
+SELECT comment FROM system.tables WHERE name = 'base';
+SELECT comment FROM system.tables WHERE name = 'copy_without_comment';
+SELECT comment FROM system.tables WHERE name = 'copy_with_comment';