added SHOW CREATE DATABASE query [#CLICKHOUSE-3590]

dbms/src/Databases/DatabaseOrdinary.cpp

@@ -45,6 +45,12 @@ namespace detail
     {
         return base_path + (endsWith(base_path, "/") ? "" : "/") + escapeForFileName(table_name) + ".sql";
     }
+
+    String getDatabaseMetadataPath(const String & base_path)
+    {
+        return (endsWith(base_path, "/") ? base_path.substr(0, base_path.size() - 1) : base_path) + ".sql";
+    }
+
 }
 
 static void loadTable(
@@ -332,16 +338,21 @@ void DatabaseOrdinary::removeTable(
 
 static ASTPtr getCreateQueryImpl(const String & path, const String & table_name)
 {
-    String table_metadata_path = detail::getTableMetadataPath(path, table_name);
+    String metadata_path;
+
+    if (table_name.empty())
+        metadata_path = detail::getDatabaseMetadataPath(path);
+    else
+        metadata_path = detail::getTableMetadataPath(path, table_name);
 
     String query;
     {
-        ReadBufferFromFile in(table_metadata_path, 4096);
+        ReadBufferFromFile in(metadata_path, 4096);
         readStringUntilEOF(query, in);
     }
 
     ParserCreateQuery parser;
-    return parseQuery(parser, query.data(), query.data() + query.size(), "in file " + table_metadata_path);
+    return parseQuery(parser, query.data(), query.data() + query.size(), "in file " + metadata_path);
 }
 
 

dbms/src/Databases/IDatabase.h

@@ -124,7 +124,8 @@ public:
         const Context & context,
         const String & name) = 0;
 
-    /// Get the CREATE TABLE query for the table. It can also provide information for detached tables for which there is metadata.
+    /// Get the CREATE TABLE query for the table or CREATE DATABASE query for database if name is empty.
+    /// It can also provide information for detached tables for which there is metadata.
     virtual ASTPtr getCreateQuery(
         const Context & context,
         const String & name) const = 0;

dbms/src/Interpreters/InterpreterFactory.cpp

@@ -107,7 +107,11 @@ std::unique_ptr<IInterpreter> InterpreterFactory::get(ASTPtr & query, Context &
     {
         return std::make_unique<InterpreterExistsQuery>(query, context);
     }
-    else if (typeid_cast<ASTShowCreateQuery *>(query.get()))
+    else if (typeid_cast<ASTShowCreateTableQuery *>(query.get()))
+    {
+        return std::make_unique<InterpreterShowCreateQuery>(query, context);
+    }
+    else if (typeid_cast<ASTShowCreateDatabaseQuery *>(query.get()))
     {
         return std::make_unique<InterpreterShowCreateQuery>(query, context);
     }

dbms/src/Interpreters/InterpreterShowCreateQuery.cpp

@@ -39,7 +39,7 @@ Block InterpreterShowCreateQuery::getSampleBlock()
 
 BlockInputStreamPtr InterpreterShowCreateQuery::executeImpl()
 {
-    const ASTShowCreateQuery & ast = typeid_cast<const ASTShowCreateQuery &>(*query_ptr);
+    const auto & ast = dynamic_cast<const ASTQueryWithTableAndOutput &>(*query_ptr);
 
     if (ast.temporary && !ast.database.empty())
         throw Exception("Temporary databases are not possible.", ErrorCodes::SYNTAX_ERROR);

dbms/src/Parsers/ParserTablePropertiesQuery.cpp

@@ -19,6 +19,7 @@ bool ParserTablePropertiesQuery::parseImpl(Pos & pos, ASTPtr & node, Expected &
     ParserKeyword s_desc("DESC");
     ParserKeyword s_show("SHOW");
     ParserKeyword s_create("CREATE");
+    ParserKeyword s_database("DATABASE");
     ParserKeyword s_table("TABLE");
     ParserToken s_dot(TokenType::Dot);
     ParserIdentifier name_p;
@@ -27,6 +28,8 @@ bool ParserTablePropertiesQuery::parseImpl(Pos & pos, ASTPtr & node, Expected &
     ASTPtr table;
     std::shared_ptr<ASTQueryWithTableAndOutput> query;
 
+    bool parse_only_database_name = false;
+
     if (s_exists.ignore(pos, expected))
     {
         query = std::make_shared<ASTExistsQuery>();
@@ -36,26 +39,40 @@ bool ParserTablePropertiesQuery::parseImpl(Pos & pos, ASTPtr & node, Expected &
         if (!s_create.ignore(pos, expected))
             return false;
 
-        query = std::make_shared<ASTShowCreateQuery>();
+        if (s_database.ignore(pos, expected))
+        {
+            parse_only_database_name = true;
+            query = std::make_shared<ASTShowCreateDatabaseQuery>();
+        }
+        else
+            query = std::make_shared<ASTShowCreateTableQuery>();
     }
     else
     {
         return false;
     }
 
-    if (s_temporary.ignore(pos, expected))
+    if (parse_only_database_name)
-        query->temporary = true;
-
-    s_table.ignore(pos, expected);
-
-    if (!name_p.parse(pos, table, expected))
-        return false;
-
-    if (s_dot.ignore(pos, expected))
     {
-        database = table;
+        if (!name_p.parse(pos, database, expected))
+            return false;
+    }
+    else
+    {
+        if (s_temporary.ignore(pos, expected))
+            query->temporary = true;
+
+        s_table.ignore(pos, expected);
+
         if (!name_p.parse(pos, table, expected))
             return false;
+
+        if (s_dot.ignore(pos, expected))
+        {
+            database = table;
+            if (!name_p.parse(pos, table, expected))
+                return false;
+        }
     }
 
     if (database)

dbms/src/Parsers/TablePropertiesQueriesASTs.h

@@ -12,12 +12,18 @@ struct ASTExistsQueryIDAndQueryNames
     static constexpr auto Query = "EXISTS TABLE";
 };
 
-struct ASTShowCreateQueryIDAndQueryNames
+struct ASTShowCreateTableQueryIDAndQueryNames
 {
-    static constexpr auto ID = "ShowCreateQuery";
+    static constexpr auto ID = "ShowCreateTableQuery";
     static constexpr auto Query = "SHOW CREATE TABLE";
 };
 
+struct ASTShowCreateDatabaseQueryIDAndQueryNames
+{
+    static constexpr auto ID = "ShowCreateDatabaseQuery";
+    static constexpr auto Query = "SHOW CREATE DATABASE";
+};
+
 struct ASTDescribeQueryExistsQueryIDAndQueryNames
 {
     static constexpr auto ID = "DescribeQuery";
@@ -25,7 +31,17 @@ struct ASTDescribeQueryExistsQueryIDAndQueryNames
 };
 
 using ASTExistsQuery = ASTQueryWithTableAndOutputImpl<ASTExistsQueryIDAndQueryNames>;
-using ASTShowCreateQuery = ASTQueryWithTableAndOutputImpl<ASTShowCreateQueryIDAndQueryNames>;
+using ASTShowCreateTableQuery = ASTQueryWithTableAndOutputImpl<ASTShowCreateTableQueryIDAndQueryNames>;
+
+class ASTShowCreateDatabaseQuery : public ASTQueryWithTableAndOutputImpl<ASTShowCreateDatabaseQueryIDAndQueryNames>
+{
+protected:
+    void formatQueryImpl(const FormatSettings & settings, FormatState &, FormatStateStacked) const override
+    {
+        settings.ostr << (settings.hilite ? hilite_keyword : "") << ASTShowCreateDatabaseQueryIDAndQueryNames::Query
+                      << " " << (settings.hilite ? hilite_none : "") << backQuoteIfNeed(database);
+    }
+};
 
 class ASTDescribeQuery : public ASTQueryWithOutput
 {