Fixed code review issues

src/Common/escapeString.cpp

@@ -0,0 +1,16 @@
+#include <Common/escapeString.h>
+
+#include <IO/WriteBufferFromString.h>
+#include <IO/WriteHelpers.h>
+
+namespace DB
+{
+
+String escapeString(std::string_view value)
+{
+    WriteBufferFromOwnString buf;
+    writeEscapedString(value, buf);
+    return buf.str();
+}
+
+}

src/Common/escapeString.h

@@ -0,0 +1,10 @@
+#pragma once
+
+#include <base/types.h>
+
+namespace DB
+{
+
+String escapeString(std::string_view value);
+
+}

src/Interpreters/InterpreterShowColumnsQuery.cpp

@@ -1,6 +1,7 @@
 #include <Interpreters/InterpreterShowColumnsQuery.h>
 
 #include <Common/quoteString.h>
+#include <Common/escapeString.h>
 #include <IO/Operators.h>
 #include <IO/WriteBufferFromString.h>
 #include <Parsers/ASTShowColumnsQuery.h>
@@ -31,12 +32,8 @@ String InterpreterShowColumnsQuery::getRewrittenQuery()
 
     WriteBufferFromOwnString buf_database;
     String resolved_database = getContext()->resolveDatabase(query.database);
-    writeEscapedString(resolved_database, buf_database);
+    String database = escapeString(resolved_database);
-    String database = buf_database.str();
+    String table = escapeString(query.table);
-
-    WriteBufferFromOwnString buf_table;
-    writeEscapedString(query.table, buf_table);
-    String table = buf_table.str();
 
     String rewritten_query;
     if (use_mysql_types)

src/Interpreters/InterpreterShowIndexesQuery.cpp

@@ -1,6 +1,7 @@
 #include <Interpreters/InterpreterShowIndexesQuery.h>
 
 #include <Common/quoteString.h>
+#include <Common/escapeString.h>
 #include <IO/Operators.h>
 #include <IO/WriteBufferFromString.h>
 #include <Parsers/ASTShowIndexesQuery.h>
@@ -23,16 +24,9 @@ InterpreterShowIndexesQuery::InterpreterShowIndexesQuery(const ASTPtr & query_pt
 String InterpreterShowIndexesQuery::getRewrittenQuery()
 {
     const auto & query = query_ptr->as<ASTShowIndexesQuery &>();
-
+    String table = escapeString(query.table);
-    WriteBufferFromOwnString buf_table;
-    writeEscapedString(query.table, buf_table);
-    String table = buf_table.str();
-
-    WriteBufferFromOwnString buf_database;
     String resolved_database = getContext()->resolveDatabase(query.database);
-    writeEscapedString(resolved_database, buf_database);
+    String database = escapeString(resolved_database);
-    String database = buf_database.str();
-
     String where_expression = query.where_expression ? fmt::format("WHERE ({})", query.where_expression) : "";
 
     String rewritten_query = fmt::format(R"(

src/Interpreters/InterpreterShowSettingQuery.cpp

@@ -1,10 +1,7 @@
 #include <Interpreters/InterpreterShowSettingQuery.h>
 
-#include <Common/quoteString.h>
+#include <Common/escapeString.h>
-#include <IO/Operators.h>
-#include <IO/WriteBufferFromString.h>
 #include <Parsers/ASTShowSettingQuery.h>
-#include <Parsers/formatAST.h>
 #include <Interpreters/Context.h>
 #include <Interpreters/executeQuery.h>
 
@@ -23,7 +20,7 @@ InterpreterShowSettingQuery::InterpreterShowSettingQuery(const ASTPtr & query_pt
 String InterpreterShowSettingQuery::getRewrittenQuery()
 {
     const auto & query = query_ptr->as<ASTShowSettingQuery &>();
-    return fmt::format(R"(SELECT value FROM system.settings WHERE name = '{0}')", query.getSettingName());
+    return fmt::format(R"(SELECT value FROM system.settings WHERE name = '{0}')", escapeString(query.getSettingName()));
 }
 
 

src/Parsers/ParserShowSettingQuery.cpp

@@ -1,13 +1,10 @@
 #include <Parsers/ParserShowSettingQuery.h>
 
 #include <Parsers/ASTIdentifier_fwd.h>
-#include <Parsers/ASTLiteral.h>
 #include <Parsers/ASTShowSettingQuery.h>
 #include <Parsers/CommonParsers.h>
 #include <Parsers/ExpressionElementParsers.h>
-#include <Parsers/ExpressionListParsers.h>
 
-#include <boost/algorithm/string.hpp>
 
 namespace DB
 {

src/Parsers/ParserShowSettingQuery.h

@@ -5,8 +5,8 @@
 namespace DB
 {
 
-/** Parses queries of the form
+/** Parses queries of the form:
- * SHOW SETTING setting_name
+  * SHOW SETTING [setting_name]
   */
 class ParserShowSettingQuery : public IParserBase
 {

tests/queries/0_stateless/02905_show_setting_query.reference

@@ -1 +1,2 @@
 1
+2

tests/queries/0_stateless/02905_show_setting_query.sql

@@ -1,2 +1,7 @@
 SET max_threads = 1;
 SHOW SETTING max_threads;
+
+SET max_threads = 2;
+SHOW SETTING max_threads;
+
+SHOW SETTING `max_threads' OR name = 'max_memory_usage`;