fixed comment test.

remove ColumnComment struct.
style fixes

dbms/src/Interpreters/InterpreterCreateQuery.cpp

@@ -220,9 +220,9 @@ static ParsedColumns parseColumns(const ASTExpressionList & column_list_ast, con
                 default_expr_list->children.emplace_back(setAlias(col_decl.default_expression->clone(), col_decl.name));
         }
 
-        if (col_decl.comment_expression)
+        if (!col_decl.comment.empty())
         {
-            comments.emplace(col_decl.name, ColumnComment{col_decl.comment_expression});
+            comments.emplace(col_decl.name, col_decl.comment);
         }
     }
 
@@ -351,7 +351,7 @@ ASTPtr InterpreterCreateQuery::formatColumns(const ColumnsDescription & columns)
         const auto comments_it = columns.comments.find(column.name);
         if (comments_it != std::end(columns.comments))
         {
-            column_declaration->comment_expression = comments_it->second.expression->clone();
+            column_declaration->comment = comments_it->second;
         }
 
         columns_list->children.push_back(column_declaration_ptr);

dbms/src/Interpreters/InterpreterDescribeQuery.cpp

@@ -45,6 +45,10 @@ Block InterpreterDescribeQuery::getSampleBlock()
     col.name = "default_expression";
     block.insert(col);
 
+    // TODO: may be it unneeded
+    col.name = "comment_expression";
+    block.insert(col);
+
     return block;
 }
 
@@ -55,6 +59,7 @@ BlockInputStreamPtr InterpreterDescribeQuery::executeImpl()
 
     NamesAndTypesList columns;
     ColumnDefaults column_defaults;
+    ColumnComments column_comments;
     StoragePtr table;
 
     auto table_expression = typeid_cast<const ASTTableExpression *>(ast.table_expression.get());
@@ -101,6 +106,7 @@ BlockInputStreamPtr InterpreterDescribeQuery::executeImpl()
         auto table_lock = table->lockStructure(false, __PRETTY_FUNCTION__);
         columns = table->getColumns().getAll();
         column_defaults = table->getColumns().defaults;
+        column_comments = table->getColumns().comments;
     }
 
     Block sample_block = getSampleBlock();
@@ -111,16 +117,26 @@ BlockInputStreamPtr InterpreterDescribeQuery::executeImpl()
         res_columns[0]->insert(column.name);
         res_columns[1]->insert(column.type->getName());
 
-        const auto it = column_defaults.find(column.name);
+        const auto defaults_it = column_defaults.find(column.name);
-        if (it == std::end(column_defaults))
+        if (defaults_it == std::end(column_defaults))
         {
             res_columns[2]->insertDefault();
             res_columns[3]->insertDefault();
         }
         else
         {
-            res_columns[2]->insert(toString(it->second.kind));
+            res_columns[2]->insert(toString(defaults_it->second.kind));
-            res_columns[3]->insert(queryToString(it->second.expression));
+            res_columns[3]->insert(queryToString(defaults_it->second.expression));
+        }
+
+        const auto comments_it = column_comments.find(column.name);
+        if (comments_it == std::end(column_comments))
+        {
+            res_columns[4]->insertDefault();
+        }
+        else
+        {
+            res_columns[4]->insert(comments_it->second);
         }
     }
 

dbms/src/Parsers/ASTAlterQuery.cpp

@@ -146,7 +146,7 @@ void ASTAlterCommand::formatImpl(
         settings.ostr << (settings.hilite ? hilite_keyword : "") << indent_str << "COMMENT COLUMN " << (settings.hilite ? hilite_none : "");
         column->formatImpl(settings, state, frame);
         settings.ostr << " ";
-        comment->formatImpl(settings, state, frame);
+        // comment->formatImpl(settings, state, frame);
     }
     else
         throw Exception("Unexpected type of ALTER", ErrorCodes::UNEXPECTED_AST_STRUCTURE);

dbms/src/Parsers/ASTColumnDeclaration.h

@@ -15,7 +15,7 @@ public:
     ASTPtr type;
     String default_specifier;
     ASTPtr default_expression;
-    ASTPtr comment_expression;
+    String comment;
 
     String getID() const override { return "ColumnDeclaration_" + name; }
 
@@ -36,12 +36,6 @@ public:
             res->children.push_back(res->default_expression);
         }
 
-        if (comment_expression)
-        {
-            res->comment_expression = comment_expression->clone();
-            res->children.push_back(res->comment_expression);
-        }
-
         return res;
     }
 
@@ -63,10 +57,9 @@ public:
             default_expression->formatImpl(settings, state, frame);
         }
 
-        if (comment_expression)
+        if (!comment.empty())
         {
-            settings.ostr << ' ' << (settings.hilite ? hilite_keyword : "") << "COMMENT" << (settings.hilite ? hilite_none : "") << ' ';
+            settings.ostr << ' ' << (settings.hilite ? hilite_none : "") << "COMMENT" << (settings.hilite ? hilite_none : "") << ' ' << comment;
-            comment_expression->formatImpl(settings, state, frame);
         }
     }
 };

dbms/src/Parsers/ParserCreateQuery.h

@@ -6,6 +6,7 @@
 #include <Parsers/ASTNameTypePair.h>
 #include <Parsers/ASTColumnDeclaration.h>
 #include <Parsers/ASTIdentifier.h>
+#include <Parsers/ASTLiteral.h>
 #include <Parsers/CommonParsers.h>
 #include <Common/typeid_cast.h>
 #include <Poco/String.h>
@@ -175,7 +176,8 @@ bool IParserColumnDeclaration<NameParser>::parseImpl(Pos & pos, ASTPtr & node, E
 
     if (comment_expression)
     {
-        column_declaration->comment_expression = comment_expression;
+        auto & literal_value = typeid_cast<ASTLiteral &>(*comment_expression).value;
+        column_declaration->comment = literal_value.safeGet<String>();
         column_declaration->children.push_back(std::move(comment_expression));
     }
 

dbms/src/Parsers/ParserTablePropertiesQuery.h

@@ -7,7 +7,6 @@
 namespace DB
 {
 
-// TODO: возможно тут тоже надо разобраться
 /** Query (EXISTS | SHOW CREATE) [TABLE] [db.]name [FORMAT format]
   */
 class ParserTablePropertiesQuery : public IParserBase

dbms/src/Storages/AlterCommands.cpp

@@ -94,9 +94,10 @@ std::optional<AlterCommand> AlterCommand::parse(const ASTAlterCommand * command_
     {
         AlterCommand command;
         command.type = COMMENT_COLUMN;
-        const auto & ast_identifier = typeid_cast<ASTIdentifier&>(*command_ast->column);
+        const auto & ast_identifier = typeid_cast<ASTIdentifier &>(*command_ast->column);
         command.column_name = ast_identifier.name;
-        command.comment_expression = command_ast->comment;
+        const auto & ast_comment = typeid_cast<ASTLiteral &>(*command_ast->comment);
+        command.comment = ast_comment.value.get<String>();
         return command;
     }
     else
@@ -249,7 +250,7 @@ void AlterCommand::apply(ColumnsDescription & columns_description) const
     else if (type == COMMENT_COLUMN)
     {
 
-        columns_description.comments[column_name].expression = comment_expression;
+        columns_description.comments[column_name] = comment;
     }
     else
         throw Exception("Wrong parameter type in ALTER query", ErrorCodes::LOGICAL_ERROR);

dbms/src/Storages/AlterCommands.h

@@ -36,7 +36,7 @@ struct AlterCommand
 
     ColumnDefaultKind default_kind{};
     ASTPtr default_expression{};
-    ASTPtr comment_expression;
+    String comment;
 
     /// For ADD - after which column to add a new one. If an empty string, add to the end. To add to the beginning now it is impossible.
     String after_column;
@@ -47,9 +47,9 @@ struct AlterCommand
     AlterCommand() = default;
     AlterCommand(const Type type, const String & column_name, const DataTypePtr & data_type,
                  const ColumnDefaultKind default_kind, const ASTPtr & default_expression,
-                 const String & after_column = String{}, const ASTPtr & comment_expression = nullptr)
+                 const String & after_column = String{}, const String & comment = "")
         : type{type}, column_name{column_name}, data_type{data_type}, default_kind{default_kind},
-        default_expression{default_expression}, comment_expression(comment_expression), after_column{after_column}
+        default_expression{default_expression}, comment(comment), after_column{after_column}
     {}
 
     static std::optional<AlterCommand> parse(const ASTAlterCommand * command);

dbms/src/Storages/ColumnComment.cpp

@@ -1,7 +0,0 @@
-#include <Parsers/queryToString.h>
-#include <Storages/ColumnComment.h>
-
-bool DB::operator== (const DB::ColumnComment& lhs, const DB::ColumnComment& rhs)
-{
-    return queryToString(lhs.expression) == queryToString(rhs.expression);
-}

dbms/src/Storages/ColumnComment.h

@@ -8,13 +8,6 @@
 namespace DB
 {
 
-struct ColumnComment
+using ColumnComments = std::unordered_map<std::string, String>;
-{
-    ASTPtr expression;
-};
-
-bool operator== (const ColumnComment& lhs, const ColumnComment& rhs);
-
-using ColumnComments = std::unordered_map<std::string, ColumnComment>;
 
 }

dbms/src/Storages/ColumnsDescription.cpp

@@ -1,4 +1,5 @@
 #include <Storages/ColumnsDescription.h>
+#include <Parsers/ASTLiteral.h>
 #include <Parsers/ExpressionListParsers.h>
 #include <Parsers/parseQuery.h>
 #include <Parsers/queryToString.h>
@@ -10,6 +11,7 @@
 #include <IO/ReadBufferFromString.h>
 #include <DataTypes/DataTypeFactory.h>
 #include <Common/Exception.h>
+#include <Common/typeid_cast.h>
 
 #include <ext/collection_cast.h>
 #include <ext/map.h>
@@ -82,7 +84,7 @@ String ColumnsDescription::toString() const
             writeChar(' ', buf);
             writeText(column.type->getName(), buf);
 
-            const bool exist_comment = comments_it != std::end(comments) && !comments_it->second.expression;
+            const bool exist_comment = comments_it != std::end(comments);
             if (defaults_it != std::end(defaults))
             {
                 writeChar('\t', buf);
@@ -98,7 +100,7 @@ String ColumnsDescription::toString() const
             if (exist_comment)
             {
                 writeChar('\t', buf);
-                writeText(queryToString(comments_it->second.expression), buf);
+                writeText(comments_it->second, buf);
             }
 
             writeChar('\n', buf);
@@ -146,7 +148,7 @@ std::optional<ParsedDefaultInfo> parseDefaulfInfo(ReadBufferFromString & buf)
     return ParsedDefaultInfo{default_kind, std::move(default_expr)};
 }
 
-ASTPtr parseCommentExpr(ReadBufferFromString& buf)
+String parseComment(ReadBufferFromString& buf)
 {
     if (*buf.position() == '\n')
     {
@@ -154,12 +156,9 @@ ASTPtr parseCommentExpr(ReadBufferFromString& buf)
     }
 
     ParserExpression parser_expr;
-    String comment_expr_str;
+    String comment;
-    readText(comment_expr_str, buf);
+    readText(comment, buf); // This is wrong may be
-    const char * begin = comment_expr_str.data();
+    return comment;
-    const auto end = begin + comment_expr_str.size();
-    ASTPtr comment_expr = parseQuery(parser_expr, begin, end, "comment_expression", 0);
-    return comment_expr;
 }
 
 ColumnsDescription ColumnsDescription::parse(const String & str)
@@ -209,10 +208,10 @@ ColumnsDescription ColumnsDescription::parse(const String & str)
             result.defaults.emplace(column_name, ColumnDefault{default_kind, default_expr});
         }
 
-        const auto comment_expr = parseCommentExpr(buf);
+        const auto comment = parseComment(buf);
-        if (comment_expr)
+        if (!comment.empty())
         {
-            result.comments.emplace(column_name, ColumnComment{comment_expr});
+            result.comments.emplace(column_name, comment);
         }
 
         assertChar('\n', buf);

dbms/src/Storages/System/StorageSystemColumns.cpp

@@ -186,9 +186,8 @@ protected:
                     }
                     else
                     {
-                        const auto & literal = typeid_cast<ASTLiteral*>(it->second.expression.get());
                         if (columns_mask[src_index++])
-                            res_columns[res_index++]->insert(literal->value.get<String>());
+                            res_columns[res_index++]->insert(it->second);
                     }
                 }
 

dbms/tests/queries/0_stateless/00725_comment_columns.reference

@@ -1,4 +1,4 @@
-CREATE TABLE default.check_query_comment_column ( first_column UInt8 DEFAULT 1 COMMENT \'first comment\',  fourth_column UInt8 COMMENT \'fourth comment\',  fifth_column UInt8,  second_column UInt8 MATERIALIZED first_column COMMENT \'second comment\',  third_column UInt8 ALIAS second_column COMMENT \'third comment\') ENGINE = TinyLog
+CREATE TABLE test.check_query_comment_column ( first_column UInt8 DEFAULT 1 COMMENT \'first comment\',  fourth_column UInt8 COMMENT \'fourth comment\',  fifth_column UInt8,  second_column UInt8 MATERIALIZED first_column COMMENT \'second comment\',  third_column UInt8 ALIAS second_column COMMENT \'third comment\') ENGINE = TinyLog
 ┌─table──────────────────────┬─name──────────┬─comment────────┐
 │ check_query_comment_column │ first_column  │ first comment  │
 │ check_query_comment_column │ fourth_column │ fourth comment │
@@ -6,7 +6,7 @@ CREATE TABLE default.check_query_comment_column ( first_column UInt8 DEFAULT 1 C
 │ check_query_comment_column │ second_column │ second comment │
 │ check_query_comment_column │ third_column  │ third comment  │
 └────────────────────────────┴───────────────┴────────────────┘
-CREATE TABLE default.check_query_comment_column ( first_column UInt8 DEFAULT 1 COMMENT \'another first column\',  fourth_column UInt8 COMMENT \'another fourth column\',  fifth_column UInt8 COMMENT \'another fifth column\',  second_column UInt8 MATERIALIZED first_column COMMENT \'another second column\',  third_column UInt8 ALIAS second_column COMMENT \'another third column\') ENGINE = TinyLog
+CREATE TABLE test.check_query_comment_column ( first_column UInt8 DEFAULT 1 COMMENT \'another first column\',  fourth_column UInt8 COMMENT \'another fourth column\',  fifth_column UInt8 COMMENT \'another fifth column\',  second_column UInt8 MATERIALIZED first_column COMMENT \'another second column\',  third_column UInt8 ALIAS second_column COMMENT \'another third column\') ENGINE = TinyLog
 ┌─table──────────────────────┬─name──────────┬─comment───────────────┐
 │ check_query_comment_column │ first_column  │ another first column  │
 │ check_query_comment_column │ fourth_column │ another fourth column │
@@ -14,13 +14,13 @@ CREATE TABLE default.check_query_comment_column ( first_column UInt8 DEFAULT 1 C
 │ check_query_comment_column │ second_column │ another second column │
 │ check_query_comment_column │ third_column  │ another third column  │
 └────────────────────────────┴───────────────┴───────────────────────┘
-CREATE TABLE default.check_query_comment_column ( first_column Date COMMENT \'first comment\',  second_column UInt8 COMMENT \'second comment\',  third_column UInt8 COMMENT \'third comment\') ENGINE = MergeTree(first_column, (second_column, second_column), 8192)
+CREATE TABLE test.check_query_comment_column ( first_column Date COMMENT \'first comment\',  second_column UInt8 COMMENT \'second comment\',  third_column UInt8 COMMENT \'third comment\') ENGINE = MergeTree(first_column, (second_column, second_column), 8192)
 ┌─table──────────────────────┬─name──────────┬─comment────────┐
 │ check_query_comment_column │ first_column  │ first comment  │
 │ check_query_comment_column │ second_column │ second comment │
 │ check_query_comment_column │ third_column  │ third comment  │
 └────────────────────────────┴───────────────┴────────────────┘
-CREATE TABLE default.check_query_comment_column ( first_column Date COMMENT \'another first comment\',  second_column UInt8 COMMENT \'another second comment\',  third_column UInt8 COMMENT \'another third comment\') ENGINE = MergeTree(first_column, (second_column, second_column), 8192)
+CREATE TABLE test.check_query_comment_column ( first_column Date COMMENT \'another first comment\',  second_column UInt8 COMMENT \'another second comment\',  third_column UInt8 COMMENT \'another third comment\') ENGINE = MergeTree(first_column, (second_column, second_column), 8192)
 ┌─table──────────────────────┬─name──────────┬─comment────────────────┐
 │ check_query_comment_column │ first_column  │ another first comment  │
 │ check_query_comment_column │ second_column │ another second comment │

dbms/tests/queries/0_stateless/00725_comment_columns.sql

@@ -1,6 +1,7 @@
-DROP TABLE IF EXISTS check_query_comment_column;
+CREATE DATABASE IF NOT EXISTS test;
+DROP TABLE IF EXISTS test.check_query_comment_column;
 
-CREATE TABLE check_query_comment_column
+CREATE TABLE test.check_query_comment_column
   (
     first_column UInt8 DEFAULT 1 COMMENT 'first comment',
     second_column UInt8 MATERIALIZED first_column COMMENT 'second comment',
@@ -9,52 +10,54 @@ CREATE TABLE check_query_comment_column
     fifth_column UInt8
   ) ENGINE = TinyLog;
 
-SHOW CREATE TABLE check_query_comment_column;
+SHOW CREATE TABLE test.check_query_comment_column;
 
 SELECT table, name, comment
 FROM system.columns
-WHERE table = 'check_query_comment_column'
+WHERE table = 'check_query_comment_column' AND database = 'test'
 FORMAT PrettyCompactNoEscapes;
 
-ALTER TABLE check_query_comment_column
+ALTER TABLE test.check_query_comment_column
   COMMENT COLUMN first_column 'another first column',
   COMMENT COLUMN second_column 'another second column',
   COMMENT COLUMN third_column 'another third column',
   COMMENT COLUMN fourth_column 'another fourth column',
   COMMENT COLUMN fifth_column 'another fifth column';
 
-SHOW CREATE TABLE check_query_comment_column;
+SHOW CREATE TABLE test.check_query_comment_column;
 
 SELECT table, name, comment
 FROM system.columns
-WHERE table = 'check_query_comment_column'
+WHERE table = 'check_query_comment_column' AND database = 'test'
 FORMAT PrettyCompactNoEscapes;
 
-DROP TABLE IF EXISTS check_query_comment_column;
+DROP TABLE IF EXISTS test.check_query_comment_column;
 
 
-CREATE TABLE check_query_comment_column
+CREATE TABLE test.check_query_comment_column
   (
     first_column Date COMMENT 'first comment',
     second_column UInt8 COMMENT 'second comment',
     third_column UInt8 COMMENT 'third comment'
   ) ENGINE = MergeTree(first_column, (second_column, second_column), 8192);
 
-SHOW CREATE TABLE check_query_comment_column;
+SHOW CREATE TABLE test.check_query_comment_column;
 
 SELECT table, name, comment
 FROM system.columns
-WHERE table = 'check_query_comment_column'
+WHERE table = 'check_query_comment_column' AND database = 'test'
 FORMAT PrettyCompactNoEscapes;
 
-ALTER TABLE check_query_comment_column
+ALTER TABLE test.check_query_comment_column
   COMMENT COLUMN first_column 'another first comment',
   COMMENT COLUMN second_column 'another second comment',
   COMMENT COLUMN third_column 'another third comment';
 
-SHOW CREATE TABLE check_query_comment_column;
+SHOW CREATE TABLE test.check_query_comment_column;
 
 SELECT table, name, comment
 FROM system.columns
-WHERE table = 'check_query_comment_column'
+WHERE table = 'check_query_comment_column' and database = 'test'
 FORMAT PrettyCompactNoEscapes;
+
+DROP table test.check_query_comment_column;