ClickHouse/programs/client/Client.cpp

#include "TestHint.h"
#include "ConnectionParameters.h"
#include "Suggest.h"

#if USE_REPLXX
#   include <common/ReplxxLineReader.h>
#elif defined(USE_READLINE) && USE_READLINE
#   include <common/ReadlineLineReader.h>
#else
#   include <common/LineReader.h>
#endif

#include <stdlib.h>
#include <fcntl.h>
#include <signal.h>
#include <map>
#include <iostream>
#include <fstream>
#include <iomanip>
#include <unordered_set>
#include <algorithm>
#include <optional>
#include <ext/scope_guard.h>
#include <boost/program_options.hpp>
#include <boost/algorithm/string/replace.hpp>
#include <Poco/String.h>
#include <Poco/File.h>
#include <Poco/Util/Application.h>
#include <common/find_symbols.h>
#include <common/LineReader.h>
#include <Common/ClickHouseRevision.h>
#include <Common/Stopwatch.h>
#include <Common/Exception.h>
#include <Common/ShellCommand.h>
#include <Common/UnicodeBar.h>
#include <Common/formatReadable.h>
#include <Common/NetException.h>
#include <Common/Throttler.h>
#include <Common/StringUtils/StringUtils.h>
#include <Common/typeid_cast.h>
#include <Common/Config/ConfigProcessor.h>
#include <Core/Types.h>
#include <Core/QueryProcessingStage.h>
#include <Core/ExternalTable.h>
#include <IO/ReadBufferFromFileDescriptor.h>
#include <IO/WriteBufferFromFileDescriptor.h>
#include <IO/WriteBufferFromFile.h>
#include <IO/ReadBufferFromMemory.h>
#include <IO/ReadBufferFromString.h>
#include <IO/ReadHelpers.h>
#include <IO/WriteHelpers.h>
#include <IO/Operators.h>
#include <IO/UseSSL.h>
#include <DataStreams/AsynchronousBlockInputStream.h>
#include <DataStreams/AddingDefaultsBlockInputStream.h>
#include <DataStreams/InternalTextLogsRowOutputStream.h>
#include <Parsers/ParserQuery.h>
#include <Parsers/ASTSetQuery.h>
#include <Parsers/ASTUseQuery.h>
#include <Parsers/ASTInsertQuery.h>
#include <Parsers/ASTSelectWithUnionQuery.h>
#include <Parsers/ASTQueryWithOutput.h>
#include <Parsers/ASTLiteral.h>
#include <Parsers/ASTIdentifier.h>
#include <Parsers/formatAST.h>
#include <Parsers/parseQuery.h>
#include <Interpreters/Context.h>
#include <Interpreters/InterpreterSetQuery.h>
#include <Interpreters/ReplaceQueryParameterVisitor.h>
#include <Client/Connection.h>
#include <Common/InterruptListener.h>
#include <Functions/registerFunctions.h>
#include <AggregateFunctions/registerAggregateFunctions.h>
#include <Common/Config/configReadClient.h>
#include <Storages/ColumnsDescription.h>
#include <common/argsToConfig.h>
#include <Common/TerminalSize.h>

#if !defined(ARCADIA_BUILD)
#    include <Common/config_version.h>
#endif

#ifndef __clang__
#pragma GCC optimize("-fno-var-tracking-assignments")
#endif

/// http://en.wikipedia.org/wiki/ANSI_escape_code
#define CLEAR_TO_END_OF_LINE "\033[K"


namespace DB
{

namespace ErrorCodes
{
    extern const int NETWORK_ERROR;
    extern const int NO_DATA_TO_INSERT;
    extern const int BAD_ARGUMENTS;
    extern const int UNKNOWN_PACKET_FROM_SERVER;
    extern const int UNEXPECTED_PACKET_FROM_SERVER;
    extern const int CLIENT_OUTPUT_FORMAT_SPECIFIED;
    extern const int INVALID_USAGE_OF_INPUT;
    extern const int DEADLOCK_AVOIDED;
}


class Client : public Poco::Util::Application
{
public:
    Client() = default;

private:
    using StringSet = std::unordered_set<String>;
    StringSet exit_strings
    {
        "exit", "quit", "logout",
        "учше", "йгше", "дщпщге",
        "exit;", "quit;", "logout;",
        "учшеж", "йгшеж", "дщпщгеж",
        "q", "й", "\\q", "\\Q", "\\й", "\\Й", ":q", "Жй"
    };
    bool is_interactive = true;          /// Use either interactive line editing interface or batch mode.
    bool need_render_progress = true;    /// Render query execution progress.
    bool send_logs    = false;           /// send_logs_level passed, do not use previous cursor position, to avoid overlaps with logs
    bool echo_queries = false;           /// Print queries before execution in batch mode.
    bool ignore_error = false;           /// In case of errors, don't print error message, continue to next query. Only applicable for non-interactive mode.
    bool print_time_to_stderr = false;   /// Output execution time to stderr in batch mode.
    bool stdin_is_a_tty = false;         /// stdin is a terminal.
    bool stdout_is_a_tty = false;        /// stdout is a terminal.

    std::unique_ptr<Connection> connection;    /// Connection to DB.
    String query_id;                     /// Current query_id.
    String query;                        /// Current query.

    String format;                       /// Query results output format.
    bool is_default_format = true;       /// false, if format is set in the config or command line.
    size_t format_max_block_size = 0;    /// Max block size for console output.
    String insert_format;                /// Format of INSERT data that is read from stdin in batch mode.
    size_t insert_format_max_block_size = 0; /// Max block size when reading INSERT data.
    size_t max_client_network_bandwidth = 0; /// The maximum speed of data exchange over the network for the client in bytes per second.

    bool has_vertical_output_suffix = false; /// Is \G present at the end of the query string?

    SharedContextHolder shared_context = Context::createShared();
    Context context = Context::createGlobal(shared_context.get());

    /// Buffer that reads from stdin in batch mode.
    ReadBufferFromFileDescriptor std_in {STDIN_FILENO};

    /// Console output.
    WriteBufferFromFileDescriptor std_out {STDOUT_FILENO};
    std::unique_ptr<ShellCommand> pager_cmd;
    /// The user can specify to redirect query output to a file.
    std::optional<WriteBufferFromFile> out_file_buf;
    BlockOutputStreamPtr block_out_stream;

    /// The user could specify special file for server logs (stderr by default)
    std::unique_ptr<WriteBuffer> out_logs_buf;
    String server_logs_file;
    BlockOutputStreamPtr logs_out_stream;

    String home_path;

    String current_profile;

    String prompt_by_server_display_name;

    /// Path to a file containing command history.
    String history_file;

    /// How many rows have been read or written.
    size_t processed_rows = 0;

    /// Parsed query. Is used to determine some settings (e.g. format, output file).
    ASTPtr parsed_query;

    /// The last exception that was received from the server. Is used for the return code in batch mode.
    std::unique_ptr<Exception> last_exception;

    /// If the last query resulted in exception.
    bool got_exception = false;
    int expected_server_error = 0;
    int expected_client_error = 0;
    int actual_server_error = 0;
    int actual_client_error = 0;

    UInt64 server_revision = 0;
    String server_version;
    String server_display_name;

    Stopwatch watch;

    /// The server periodically sends information about how much data was read since last time.
    Progress progress;
    bool show_progress_bar = false;

    size_t written_progress_chars = 0;
    bool written_first_block = false;

    /// External tables info.
    std::list<ExternalTable> external_tables;

    /// Dictionary with query parameters for prepared statements.
    NameToNameMap query_parameters;

    ConnectionParameters connection_parameters;

    void initialize(Poco::Util::Application & self) override
    {
        Poco::Util::Application::initialize(self);

        const char * home_path_cstr = getenv("HOME");
        if (home_path_cstr)
            home_path = home_path_cstr;

        configReadClient(config(), home_path);

        context.setApplicationType(Context::ApplicationType::CLIENT);
        context.setQueryParameters(query_parameters);

        /// settings and limits could be specified in config file, but passed settings has higher priority
        for (const auto & setting : context.getSettingsRef())
        {
            const String & name = setting.getName().toString();
            if (config().has(name) && !setting.isChanged())
                context.setSetting(name, config().getString(name));
        }

        /// Set path for format schema files
        if (config().has("format_schema_path"))
            context.setFormatSchemaPath(Poco::Path(config().getString("format_schema_path")).toString());
    }


    int main(const std::vector<std::string> & /*args*/) override
    {
        try
        {
            return mainImpl();
        }
        catch (const Exception & e)
        {
            bool print_stack_trace = config().getBool("stacktrace", false);

            std::string text = e.displayText();

            /** If exception is received from server, then stack trace is embedded in message.
              * If exception is thrown on client, then stack trace is in separate field.
              */

            auto embedded_stack_trace_pos = text.find("Stack trace");
            if (std::string::npos != embedded_stack_trace_pos && !print_stack_trace)
                text.resize(embedded_stack_trace_pos);

             std::cerr << "Code: " << e.code() << ". " << text << std::endl << std::endl;

            /// Don't print the stack trace on the client if it was logged on the server.
            /// Also don't print the stack trace in case of network errors.
            if (print_stack_trace
                && e.code() != ErrorCodes::NETWORK_ERROR
                && std::string::npos == embedded_stack_trace_pos)
            {
                std::cerr << "Stack trace:" << std::endl
                    << e.getStackTraceString();
            }

            /// If exception code isn't zero, we should return non-zero return code anyway.
            return e.code() ? e.code() : -1;
        }
        catch (...)
        {
            std::cerr << getCurrentExceptionMessage(false) << std::endl;
            return getCurrentExceptionCode();
        }
    }

    /// Should we celebrate a bit?
    static bool isNewYearMode()
    {
        time_t current_time = time(nullptr);

        /// It's bad to be intrusive.
        if (current_time % 3 != 0)
            return false;

        LocalDate now(current_time);
        return (now.month() == 12 && now.day() >= 20)
            || (now.month() == 1 && now.day() <= 5);
    }

    static bool isChineseNewYearMode(const String & local_tz)
    {
        /// Days of Dec. 20 in Chinese calendar starting from year 2019 to year 2105
        static constexpr UInt16 chineseNewYearIndicators[]
            = {18275, 18659, 19014, 19368, 19752, 20107, 20491, 20845, 21199, 21583, 21937, 22292, 22676, 23030, 23414, 23768, 24122, 24506,
               24860, 25215, 25599, 25954, 26308, 26692, 27046, 27430, 27784, 28138, 28522, 28877, 29232, 29616, 29970, 30354, 30708, 31062,
               31446, 31800, 32155, 32539, 32894, 33248, 33632, 33986, 34369, 34724, 35078, 35462, 35817, 36171, 36555, 36909, 37293, 37647,
               38002, 38386, 38740, 39095, 39479, 39833, 40187, 40571, 40925, 41309, 41664, 42018, 42402, 42757, 43111, 43495, 43849, 44233,
               44587, 44942, 45326, 45680, 46035, 46418, 46772, 47126, 47510, 47865, 48249, 48604, 48958, 49342};

        /// All time zone names are acquired from https://www.iana.org/time-zones
        static constexpr const char * chineseNewYearTimeZoneIndicators[] = {
            /// Time zones celebrating Chinese new year.
            "Asia/Shanghai",
            "Asia/Chongqing",
            "Asia/Harbin",
            "Asia/Urumqi",
            "Asia/Hong_Kong",
            "Asia/Chungking",
            "Asia/Macao",
            "Asia/Macau",
            "Asia/Taipei",
            "Asia/Singapore",

            /// Time zones celebrating Chinese new year but with different festival names. Let's not print the message for now.
            // "Asia/Brunei",
            // "Asia/Ho_Chi_Minh",
            // "Asia/Hovd",
            // "Asia/Jakarta",
            // "Asia/Jayapura",
            // "Asia/Kashgar",
            // "Asia/Kuala_Lumpur",
            // "Asia/Kuching",
            // "Asia/Makassar",
            // "Asia/Pontianak",
            // "Asia/Pyongyang",
            // "Asia/Saigon",
            // "Asia/Seoul",
            // "Asia/Ujung_Pandang",
            // "Asia/Ulaanbaatar",
            // "Asia/Ulan_Bator",
        };
        static constexpr size_t M = sizeof(chineseNewYearTimeZoneIndicators) / sizeof(chineseNewYearTimeZoneIndicators[0]);

        time_t current_time = time(nullptr);

        if (chineseNewYearTimeZoneIndicators + M
            == std::find_if(chineseNewYearTimeZoneIndicators, chineseNewYearTimeZoneIndicators + M, [&local_tz](const char * tz)
            {
                return tz == local_tz;
            }))
            return false;

        /// It's bad to be intrusive.
        if (current_time % 3 != 0)
            return false;

        auto days = DateLUT::instance().toDayNum(current_time).toUnderType();
        for (auto d : chineseNewYearIndicators)
        {
            /// Let's celebrate until Lantern Festival
            if (d <= days && d + 25u >= days)
                return true;
            else if (d > days)
                return false;
        }
        return false;
    }

    int mainImpl()
    {
        UseSSL use_ssl;

        registerFunctions();
        registerAggregateFunctions();

        /// Batch mode is enabled if one of the following is true:
        /// - -e (--query) command line option is present.
        ///   The value of the option is used as the text of query (or of multiple queries).
        ///   If stdin is not a terminal, INSERT data for the first query is read from it.
        /// - stdin is not a terminal. In this case queries are read from it.
        if (!stdin_is_a_tty || config().has("query"))
            is_interactive = false;

        std::cout << std::fixed << std::setprecision(3);
        std::cerr << std::fixed << std::setprecision(3);

        if (is_interactive)
            showClientVersion();

        is_default_format = !config().has("vertical") && !config().has("format");
        if (config().has("vertical"))
            format = config().getString("format", "Vertical");
        else
            format = config().getString("format", is_interactive ? "PrettyCompact" : "TabSeparated");

        format_max_block_size = config().getInt("format_max_block_size", context.getSettingsRef().max_block_size);

        insert_format = "Values";

        /// Setting value from cmd arg overrides one from config
        if (context.getSettingsRef().max_insert_block_size.changed)
            insert_format_max_block_size = context.getSettingsRef().max_insert_block_size;
        else
            insert_format_max_block_size = config().getInt("insert_format_max_block_size", context.getSettingsRef().max_insert_block_size);

        if (!is_interactive)
        {
            need_render_progress = config().getBool("progress", false);
            echo_queries = config().getBool("echo", false);
            ignore_error = config().getBool("ignore-error", false);
        }

        ClientInfo & client_info = context.getClientInfo();
        client_info.setInitialQuery();
        client_info.quota_key = config().getString("quota_key", "");

        connect();

        /// Initialize DateLUT here to avoid counting time spent here as query execution time.
        const auto local_tz = DateLUT::instance().getTimeZone();
        if (!context.getSettingsRef().use_client_time_zone)
        {
            const auto & time_zone = connection->getServerTimezone(connection_parameters.timeouts);
            if (!time_zone.empty())
            {
                try
                {
                    DateLUT::setDefaultTimezone(time_zone);
                }
                catch (...)
                {
                    std::cerr << "Warning: could not switch to server time zone: " << time_zone
                        << ", reason: " << getCurrentExceptionMessage(/* with_stacktrace = */ false) << std::endl
                        << "Proceeding with local time zone."
                        << std::endl << std::endl;
                }
            }
            else
            {
                std::cerr << "Warning: could not determine server time zone. "
                    << "Proceeding with local time zone."
                    << std::endl << std::endl;
            }
        }

        Strings keys;

        prompt_by_server_display_name = config().getRawString("prompt_by_server_display_name.default", "{display_name} :) ");

        config().keys("prompt_by_server_display_name", keys);

        for (const String & key : keys)
        {
            if (key != "default" && server_display_name.find(key) != std::string::npos)
            {
                prompt_by_server_display_name = config().getRawString("prompt_by_server_display_name." + key);
                break;
            }
        }

        /// Prompt may contain escape sequences including \e[ or \x1b[ sequences to set terminal color.
        {
            String unescaped_prompt_by_server_display_name;
            ReadBufferFromString in(prompt_by_server_display_name);
            readEscapedString(unescaped_prompt_by_server_display_name, in);
            prompt_by_server_display_name = std::move(unescaped_prompt_by_server_display_name);
        }

        /// Prompt may contain the following substitutions in a form of {name}.
        std::map<String, String> prompt_substitutions
        {
            {"host", connection_parameters.host},
            {"port", toString(connection_parameters.port)},
            {"user", connection_parameters.user},
            {"display_name", server_display_name},
        };

        /// Quite suboptimal.
        for (const auto & [key, value]: prompt_substitutions)
            boost::replace_all(prompt_by_server_display_name, "{" + key + "}", value);

        if (is_interactive)
        {
            if (!query_id.empty())
                throw Exception("query_id could be specified only in non-interactive mode", ErrorCodes::BAD_ARGUMENTS);
            if (print_time_to_stderr)
                throw Exception("time option could be specified only in non-interactive mode", ErrorCodes::BAD_ARGUMENTS);

            if (server_revision >= Suggest::MIN_SERVER_REVISION && !config().getBool("disable_suggestion", false))
            {
                /// Load suggestion data from the server.
                Suggest::instance().load(connection_parameters, config().getInt("suggestion_limit"));
            }

            /// Load command history if present.
            if (config().has("history_file"))
                history_file = config().getString("history_file");
            else
            {
                auto * history_file_from_env = getenv("CLICKHOUSE_HISTORY_FILE");
                if (history_file_from_env)
                    history_file = history_file_from_env;
                else if (!home_path.empty())
                    history_file = home_path + "/.clickhouse-client-history";
            }

            if (!history_file.empty() && !Poco::File(history_file).exists())
                Poco::File(history_file).createFile();

#if USE_REPLXX
            ReplxxLineReader lr(Suggest::instance(), history_file, '\\', config().has("multiline") ? ';' : 0);
#elif defined(USE_READLINE) && USE_READLINE
            ReadlineLineReader lr(Suggest::instance(), history_file, '\\', config().has("multiline") ? ';' : 0);
#else
            LineReader lr(history_file, '\\', config().has("multiline") ? ';' : 0);
#endif

            /// Enable bracketed-paste-mode only when multiquery is enabled and multiline is
            ///  disabled, so that we are able to paste and execute multiline queries in a whole
            ///  instead of erroring out, while be less intrusive.
            if (config().has("multiquery") && !config().has("multiline"))
                lr.enableBracketedPaste();

            do
            {
                auto input = lr.readLine(prompt(), ":-] ");
                if (input.empty())
                    break;

                has_vertical_output_suffix = false;
                if (input.ends_with("\\G"))
                {
                    input.resize(input.size() - 2);
                    has_vertical_output_suffix = true;
                }

                try
                {
                    if (!process(input))
                        break;
                }
                catch (const Exception & e)
                {
                    actual_client_error = e.code();
                    if (!actual_client_error || actual_client_error != expected_client_error)
                    {
                        std::cerr << std::endl
                            << "Exception on client:" << std::endl
                            << "Code: " << e.code() << ". " << e.displayText() << std::endl;

                        if (config().getBool("stacktrace", false))
                            std::cerr << "Stack trace:" << std::endl << e.getStackTraceString() << std::endl;

                        std::cerr << std::endl;

                    }

                    /// Client-side exception during query execution can result in the loss of
                    /// sync in the connection protocol.
                    /// So we reconnect and allow to enter the next query.
                    connect();
                }
            }
            while (true);

            if (isNewYearMode())
                std::cout << "Happy new year." << std::endl;
            else if (isChineseNewYearMode(local_tz))
                std::cout << "Happy Chinese new year. 春节快乐!" << std::endl;
            else
                std::cout << "Bye." << std::endl;
            return 0;
        }
        else
        {
            query_id = config().getString("query_id", "");
            nonInteractive();

            /// If exception code isn't zero, we should return non-zero return code anyway.
            if (last_exception)
                return last_exception->code() != 0 ? last_exception->code() : -1;

            return 0;
        }
    }


    void connect()
    {
        connection_parameters = ConnectionParameters(config());

        if (is_interactive)
            std::cout << "Connecting to "
                << (!connection_parameters.default_database.empty() ? "database " + connection_parameters.default_database + " at " : "")
                << connection_parameters.host << ":" << connection_parameters.port
                << (!connection_parameters.user.empty() ? " as user " + connection_parameters.user : "")
                << "." << std::endl;

        connection = std::make_unique<Connection>(
            connection_parameters.host,
            connection_parameters.port,
            connection_parameters.default_database,
            connection_parameters.user,
            connection_parameters.password,
            "client",
            connection_parameters.compression,
            connection_parameters.security);

        String server_name;
        UInt64 server_version_major = 0;
        UInt64 server_version_minor = 0;
        UInt64 server_version_patch = 0;

        if (max_client_network_bandwidth)
        {
            ThrottlerPtr throttler = std::make_shared<Throttler>(max_client_network_bandwidth, 0, "");
            connection->setThrottler(throttler);
        }

        connection->getServerVersion(connection_parameters.timeouts,
                                     server_name, server_version_major, server_version_minor, server_version_patch, server_revision);

        server_version = toString(server_version_major) + "." + toString(server_version_minor) + "." + toString(server_version_patch);

        if (server_display_name = connection->getServerDisplayName(connection_parameters.timeouts); server_display_name.empty())
        {
            server_display_name = config().getString("host", "localhost");
        }

        if (is_interactive)
        {
            std::cout << "Connected to " << server_name
                << " server version " << server_version
                << " revision " << server_revision
                << "." << std::endl << std::endl;

            auto client_version_tuple = std::make_tuple(VERSION_MAJOR, VERSION_MINOR, VERSION_PATCH);
            auto server_version_tuple = std::make_tuple(server_version_major, server_version_minor, server_version_patch);

            if (client_version_tuple < server_version_tuple)
            {
                std::cout << "ClickHouse client version is older than ClickHouse server. "
                    << "It may lack support for new features."
                    << std::endl << std::endl;
            }
            else if (client_version_tuple > server_version_tuple)
            {
                std::cout << "ClickHouse server version is older than ClickHouse client. "
                    << "It may indicate that the server is out of date and can be upgraded."
                    << std::endl << std::endl;
            }
        }
    }


    inline String prompt() const
    {
        return boost::replace_all_copy(prompt_by_server_display_name, "{database}", config().getString("database", "default"));
    }


    void nonInteractive()
    {
        String text;

        if (config().has("query"))
            text = config().getRawString("query");  /// Poco configuration should not process substitutions in form of ${...} inside query.
        else
        {
            /// If 'query' parameter is not set, read a query from stdin.
            /// The query is read entirely into memory (streaming is disabled).
            ReadBufferFromFileDescriptor in(STDIN_FILENO);
            readStringUntilEOF(text, in);
        }

        process(text);
    }


    bool process(const String & text)
    {
        if (exit_strings.end() != exit_strings.find(trim(text, [](char c){ return isWhitespaceASCII(c) || c == ';'; })))
            return false;

        const bool test_mode = config().has("testmode");
        if (config().has("multiquery"))
        {
            {   /// disable logs if expects errors
                TestHint test_hint(test_mode, text);
                if (test_hint.clientError() || test_hint.serverError())
                    process("SET send_logs_level = 'none'");
            }

            /// Several queries separated by ';'.
            /// INSERT data is ended by the end of line, not ';'.

            const char * begin = text.data();
            const char * end = begin + text.size();

            while (begin < end)
            {
                const char * pos = begin;
                ASTPtr ast = parseQuery(pos, end, true);

                if (!ast)
                {
                    if (ignore_error)
                    {
                        Tokens tokens(begin, end);
                        IParser::Pos token_iterator(tokens, context.getSettingsRef().max_parser_depth);
                        while (token_iterator->type != TokenType::Semicolon && token_iterator.isValid())
                            ++token_iterator;
                        begin = token_iterator->end;

                        continue;
                    }
                    return true;
                }

                auto * insert = ast->as<ASTInsertQuery>();

                if (insert && insert->data)
                {
                    pos = find_first_symbols<'\n'>(insert->data, end);
                    insert->end = pos;
                }

                String str = text.substr(begin - text.data(), pos - begin);

                begin = pos;
                while (isWhitespaceASCII(*begin) || *begin == ';')
                    ++begin;

                TestHint test_hint(test_mode, str);
                expected_client_error = test_hint.clientError();
                expected_server_error = test_hint.serverError();

                try
                {
                    auto ast_to_process = ast;
                    if (insert && insert->data)
                        ast_to_process = nullptr;

                    if (!processSingleQuery(str, ast_to_process) && !ignore_error)
                        return false;
                }
                catch (...)
                {
                    last_exception = std::make_unique<Exception>(getCurrentExceptionMessage(true), getCurrentExceptionCode());
                    actual_client_error = last_exception->code();
                    if (!ignore_error && (!actual_client_error || actual_client_error != expected_client_error))
                        std::cerr << "Error on processing query: " << str << std::endl << last_exception->message();
                    got_exception = true;
                }

                if (!test_hint.checkActual(actual_server_error, actual_client_error, got_exception, last_exception))
                    connection->forceConnected(connection_parameters.timeouts);

                if (got_exception && !ignore_error)
                {
                    if (is_interactive)
                        break;
                    else
                        return false;
                }
            }

            return true;
        }
        else
        {
            return processSingleQuery(text);
        }
    }


    bool processSingleQuery(const String & line, ASTPtr parsed_query_ = nullptr)
    {
        resetOutput();
        got_exception = false;

        if (echo_queries)
        {
            writeString(line, std_out);
            writeChar('\n', std_out);
            std_out.next();
        }

        watch.restart();

        query = line;

        /// Some parts of a query (result output and formatting) are executed client-side.
        /// Thus we need to parse the query.
        parsed_query = parsed_query_;
        if (!parsed_query)
        {
            const char * begin = query.data();
            parsed_query = parseQuery(begin, begin + query.size(), false);
        }

        if (!parsed_query)
            return true;

        processed_rows = 0;
        progress.reset();
        show_progress_bar = false;
        written_progress_chars = 0;
        written_first_block = false;

        {
            /// Temporarily apply query settings to context.
            std::optional<Settings> old_settings;
            SCOPE_EXIT({ if (old_settings) context.setSettings(*old_settings); });
            auto apply_query_settings = [&](const IAST & settings_ast)
            {
                if (!old_settings)
                    old_settings.emplace(context.getSettingsRef());
                context.applySettingsChanges(settings_ast.as<ASTSetQuery>()->changes);
            };
            const auto * insert = parsed_query->as<ASTInsertQuery>();
            if (insert && insert->settings_ast)
                apply_query_settings(*insert->settings_ast);
            /// FIXME: try to prettify this cast using `as<>()`
            const auto * with_output = dynamic_cast<const ASTQueryWithOutput *>(parsed_query.get());
            if (with_output && with_output->settings_ast)
                apply_query_settings(*with_output->settings_ast);

            connection->forceConnected(connection_parameters.timeouts);

            send_logs = context.getSettingsRef().send_logs_level != LogsLevel::none;

            ASTPtr input_function;
            if (insert && insert->select)
                insert->tryFindInputFunction(input_function);

            /// INSERT query for which data transfer is needed (not an INSERT SELECT or input()) is processed separately.
            if (insert && (!insert->select || input_function) && !insert->watch)
            {
                if (input_function && insert->format.empty())
                    throw Exception("FORMAT must be specified for function input()", ErrorCodes::INVALID_USAGE_OF_INPUT);
                processInsertQuery();
            }
            else
                processOrdinaryQuery();
        }

        /// Do not change context (current DB, settings) in case of an exception.
        if (!got_exception)
        {
            if (const auto * set_query = parsed_query->as<ASTSetQuery>())
            {
                /// Save all changes in settings to avoid losing them if the connection is lost.
                for (const auto & change : set_query->changes)
                {
                    if (change.name == "profile")
                        current_profile = change.value.safeGet<String>();
                    else
                        context.applySettingChange(change);
                }
            }

            if (const auto * use_query = parsed_query->as<ASTUseQuery>())
            {
                const String & new_database = use_query->database;
                /// If the client initiates the reconnection, it takes the settings from the config.
                config().setString("database", new_database);
                /// If the connection initiates the reconnection, it uses its variable.
                connection->setDefaultDatabase(new_database);
            }
        }

        if (is_interactive)
        {
            std::cout << std::endl
                << processed_rows << " rows in set. Elapsed: " << watch.elapsedSeconds() << " sec. ";

            if (progress.read_rows >= 1000)
                writeFinalProgress();

            std::cout << std::endl << std::endl;
        }
        else if (print_time_to_stderr)
        {
            std::cerr << watch.elapsedSeconds() << "\n";
        }

        return true;
    }


    /// Convert external tables to ExternalTableData and send them using the connection.
    void sendExternalTables()
    {
        const auto * select = parsed_query->as<ASTSelectWithUnionQuery>();
        if (!select && !external_tables.empty())
            throw Exception("External tables could be sent only with select query", ErrorCodes::BAD_ARGUMENTS);

        std::vector<ExternalTableDataPtr> data;
        for (auto & table : external_tables)
            data.emplace_back(table.getData(context));

        connection->sendExternalTablesData(data);
    }


    /// Process the query that doesn't require transferring data blocks to the server.
    void processOrdinaryQuery()
    {
        /// We will always rewrite query (even if there are no query_parameters) because it will help to find errors in query formatter.
        {
            /// Replace ASTQueryParameter with ASTLiteral for prepared statements.
            ReplaceQueryParameterVisitor visitor(query_parameters);
            visitor.visit(parsed_query);

            /// Get new query after substitutions. Note that it cannot be done for INSERT query with embedded data.
            query = serializeAST(*parsed_query);
        }

        static constexpr size_t max_retries = 10;
        for (size_t retry = 0; retry < max_retries; ++retry)
        {
            try
            {
                connection->sendQuery(
                    connection_parameters.timeouts,
                    query,
                    query_id,
                    QueryProcessingStage::Complete,
                    &context.getSettingsRef(),
                    &context.getClientInfo(),
                    true);

                sendExternalTables();
                receiveResult();

                break;
            }
            catch (const Exception & e)
            {
                /// Retry when the server said "Client should retry" and no rows has been received yet.
                if (processed_rows == 0 && e.code() == ErrorCodes::DEADLOCK_AVOIDED && retry + 1 < max_retries)
                    continue;

                throw;
            }
        }
    }


    /// Process the query that requires transferring data blocks to the server.
    void processInsertQuery()
    {
        /// Send part of query without data, because data will be sent separately.
        const auto & parsed_insert_query = parsed_query->as<ASTInsertQuery &>();
        String query_without_data = parsed_insert_query.data
            ? query.substr(0, parsed_insert_query.data - query.data())
            : query;

        if (!parsed_insert_query.data && (is_interactive || (!stdin_is_a_tty && std_in.eof())))
            throw Exception("No data to insert", ErrorCodes::NO_DATA_TO_INSERT);

        connection->sendQuery(
            connection_parameters.timeouts,
            query_without_data,
            query_id,
            QueryProcessingStage::Complete,
            &context.getSettingsRef(),
            &context.getClientInfo(),
            true);

        sendExternalTables();

        /// Receive description of table structure.
        Block sample;
        ColumnsDescription columns_description;
        if (receiveSampleBlock(sample, columns_description))
        {
            /// If structure was received (thus, server has not thrown an exception),
            /// send our data with that structure.
            sendData(sample, columns_description);
            receiveEndOfQuery();
        }
    }


    ASTPtr parseQuery(const char * & pos, const char * end, bool allow_multi_statements)
    {
        ParserQuery parser(end, true);
        ASTPtr res;

        const auto & settings = context.getSettingsRef();
        size_t max_length = 0;
        if (!allow_multi_statements)
            max_length = settings.max_query_size;

        if (is_interactive || ignore_error)
        {
            String message;
            res = tryParseQuery(parser, pos, end, message, true, "", allow_multi_statements, max_length, settings.max_parser_depth);

            if (!res)
            {
                std::cerr << std::endl << message << std::endl << std::endl;
                return nullptr;
            }
        }
        else
            res = parseQueryAndMovePosition(parser, pos, end, "", allow_multi_statements, max_length, settings.max_parser_depth);

        if (is_interactive)
        {
            std::cout << std::endl;
            formatAST(*res, std::cout);
            std::cout << std::endl << std::endl;
        }

        return res;
    }


    void sendData(Block & sample, const ColumnsDescription & columns_description)
    {
        /// If INSERT data must be sent.
        const auto * parsed_insert_query = parsed_query->as<ASTInsertQuery>();
        if (!parsed_insert_query)
            return;

        if (parsed_insert_query->data)
        {
            /// Send data contained in the query.
            ReadBufferFromMemory data_in(parsed_insert_query->data, parsed_insert_query->end - parsed_insert_query->data);
            sendDataFrom(data_in, sample, columns_description);
        }
        else if (!is_interactive)
        {
            /// Send data read from stdin.
            sendDataFrom(std_in, sample, columns_description);
        }
        else
            throw Exception("No data to insert", ErrorCodes::NO_DATA_TO_INSERT);
    }


    void sendDataFrom(ReadBuffer & buf, Block & sample, const ColumnsDescription & columns_description)
    {
        String current_format = insert_format;

        /// Data format can be specified in the INSERT query.
        if (const auto * insert = parsed_query->as<ASTInsertQuery>())
        {
            if (!insert->format.empty())
                current_format = insert->format;
        }

        BlockInputStreamPtr block_input = context.getInputFormat(
            current_format, buf, sample, insert_format_max_block_size);

        const auto & column_defaults = columns_description.getDefaults();
        if (!column_defaults.empty())
            block_input = std::make_shared<AddingDefaultsBlockInputStream>(block_input, column_defaults, context);

        BlockInputStreamPtr async_block_input = std::make_shared<AsynchronousBlockInputStream>(block_input);

        async_block_input->readPrefix();

        while (true)
        {
            Block block = async_block_input->read();

            /// Check if server send Log packet
            receiveLogs();

            /// Check if server send Exception packet
            auto packet_type = connection->checkPacket();
            if (packet_type && *packet_type == Protocol::Server::Exception)
            {
                /*
                 * We're exiting with error, so it makes sense to kill the
                 * input stream without waiting for it to complete.
                 */
                async_block_input->cancel(true);
                return;
            }

            connection->sendData(block);
            processed_rows += block.rows();

            if (!block)
                break;
        }

        async_block_input->readSuffix();
    }


    /// Flush all buffers.
    void resetOutput()
    {
        block_out_stream.reset();
        logs_out_stream.reset();

        if (pager_cmd)
        {
            pager_cmd->in.close();
            pager_cmd->wait();
        }
        pager_cmd = nullptr;

        if (out_file_buf)
        {
            out_file_buf->next();
            out_file_buf.reset();
        }

        if (out_logs_buf)
        {
            out_logs_buf->next();
            out_logs_buf.reset();
        }

        std_out.next();
    }


    /// Receives and processes packets coming from server.
    /// Also checks if query execution should be cancelled.
    void receiveResult()
    {
        InterruptListener interrupt_listener;
        bool cancelled = false;

        // TODO: get the poll_interval from commandline.
        const auto receive_timeout = connection_parameters.timeouts.receive_timeout;
        constexpr size_t default_poll_interval = 1000000; /// in microseconds
        constexpr size_t min_poll_interval = 5000; /// in microseconds
        const size_t poll_interval
            = std::max(min_poll_interval, std::min<size_t>(receive_timeout.totalMicroseconds(), default_poll_interval));

        while (true)
        {
            Stopwatch receive_watch(CLOCK_MONOTONIC_COARSE);

            while (true)
            {
                /// Has the Ctrl+C been pressed and thus the query should be cancelled?
                /// If this is the case, inform the server about it and receive the remaining packets
                /// to avoid losing sync.
                if (!cancelled)
                {
                    auto cancel_query = [&]
                    {
                        connection->sendCancel();
                        cancelled = true;
                        if (is_interactive)
                        {
                            if (written_progress_chars)
                                clearProgress();
                            std::cout << "Cancelling query." << std::endl;
                        }

                        /// Pressing Ctrl+C twice results in shut down.
                        interrupt_listener.unblock();
                    };

                    if (interrupt_listener.check())
                    {
                        cancel_query();
                    }
                    else
                    {
                        double elapsed = receive_watch.elapsedSeconds();
                        if (elapsed > receive_timeout.totalSeconds())
                        {
                            std::cout << "Timeout exceeded while receiving data from server."
                                      << " Waited for " << static_cast<size_t>(elapsed) << " seconds,"
                                      << " timeout is " << receive_timeout.totalSeconds() << " seconds." << std::endl;

                            cancel_query();
                        }
                    }
                }

                /// Poll for changes after a cancellation check, otherwise it never reached
                /// because of progress updates from server.
                if (connection->poll(poll_interval))
                    break;
            }

            if (!receiveAndProcessPacket(cancelled))
                break;
        }

        if (cancelled && is_interactive)
            std::cout << "Query was cancelled." << std::endl;
    }


    /// Receive a part of the result, or progress info or an exception and process it.
    /// Returns true if one should continue receiving packets.
    /// Output of result is suppressed if query was cancelled.
    bool receiveAndProcessPacket(bool cancelled)
    {
        Packet packet = connection->receivePacket();

        switch (packet.type)
        {
            case Protocol::Server::Data:
                if (!cancelled)
                    onData(packet.block);
                return true;

            case Protocol::Server::Progress:
                onProgress(packet.progress);
                return true;

            case Protocol::Server::ProfileInfo:
                onProfileInfo(packet.profile_info);
                return true;

            case Protocol::Server::Totals:
                if (!cancelled)
                    onTotals(packet.block);
                return true;

            case Protocol::Server::Extremes:
                if (!cancelled)
                    onExtremes(packet.block);
                return true;

            case Protocol::Server::Exception:
                onException(*packet.exception);
                last_exception = std::move(packet.exception);
                return false;

            case Protocol::Server::Log:
                onLogData(packet.block);
                return true;

            case Protocol::Server::EndOfStream:
                onEndOfStream();
                return false;

            default:
                throw Exception("Unknown packet from server", ErrorCodes::UNKNOWN_PACKET_FROM_SERVER);
        }
    }


    /// Receive the block that serves as an example of the structure of table where data will be inserted.
    bool receiveSampleBlock(Block & out, ColumnsDescription & columns_description)
    {
        while (true)
        {
            Packet packet = connection->receivePacket();

            switch (packet.type)
            {
                case Protocol::Server::Data:
                    out = packet.block;
                    return true;

                case Protocol::Server::Exception:
                    onException(*packet.exception);
                    last_exception = std::move(packet.exception);
                    return false;

                case Protocol::Server::Log:
                    onLogData(packet.block);
                    break;

                case Protocol::Server::TableColumns:
                    columns_description = ColumnsDescription::parse(packet.multistring_message[1]);
                    return receiveSampleBlock(out, columns_description);

                default:
                    throw NetException("Unexpected packet from server (expected Data, Exception or Log, got "
                        + String(Protocol::Server::toString(packet.type)) + ")", ErrorCodes::UNEXPECTED_PACKET_FROM_SERVER);
            }
        }
    }


    /// Process Log packets, exit when receive Exception or EndOfStream
    bool receiveEndOfQuery()
    {
        while (true)
        {
            Packet packet = connection->receivePacket();

            switch (packet.type)
            {
                case Protocol::Server::EndOfStream:
                    onEndOfStream();
                    return true;

                case Protocol::Server::Exception:
                    onException(*packet.exception);
                    last_exception = std::move(packet.exception);
                    return false;

                case Protocol::Server::Log:
                    onLogData(packet.block);
                    break;

                default:
                    throw NetException("Unexpected packet from server (expected Exception, EndOfStream or Log, got "
                        + String(Protocol::Server::toString(packet.type)) + ")", ErrorCodes::UNEXPECTED_PACKET_FROM_SERVER);
            }
        }
    }

    /// Process Log packets, used when inserting data by blocks
    void receiveLogs()
    {
        auto packet_type = connection->checkPacket();

        while (packet_type && *packet_type == Protocol::Server::Log)
        {
            receiveAndProcessPacket(false);
            packet_type = connection->checkPacket();
        }
    }

    void initBlockOutputStream(const Block & block)
    {
        if (!block_out_stream)
        {
            WriteBuffer * out_buf = nullptr;
            String pager = config().getString("pager", "");
            if (!pager.empty())
            {
                signal(SIGPIPE, SIG_IGN);
                pager_cmd = ShellCommand::execute(pager, true);
                out_buf = &pager_cmd->in;
            }
            else
            {
                out_buf = &std_out;
            }

            String current_format = format;

            /// The query can specify output format or output file.
            /// FIXME: try to prettify this cast using `as<>()`
            if (const auto * query_with_output = dynamic_cast<const ASTQueryWithOutput *>(parsed_query.get()))
            {
                if (query_with_output->out_file)
                {
                    const auto & out_file_node = query_with_output->out_file->as<ASTLiteral &>();
                    const auto & out_file = out_file_node.value.safeGet<std::string>();

                    out_file_buf.emplace(out_file, DBMS_DEFAULT_BUFFER_SIZE, O_WRONLY | O_EXCL | O_CREAT);
                    out_buf = &*out_file_buf;

                    // We are writing to file, so default format is the same as in non-interactive mode.
                    if (is_interactive && is_default_format)
                        current_format = "TabSeparated";
                }
                if (query_with_output->format != nullptr)
                {
                    if (has_vertical_output_suffix)
                        throw Exception("Output format already specified", ErrorCodes::CLIENT_OUTPUT_FORMAT_SPECIFIED);
                    const auto & id = query_with_output->format->as<ASTIdentifier &>();
                    current_format = id.name;
                }
            }

            if (has_vertical_output_suffix)
                current_format = "Vertical";

            block_out_stream = context.getOutputFormat(current_format, *out_buf, block);
            block_out_stream->writePrefix();
        }
    }


    void initLogsOutputStream()
    {
        if (!logs_out_stream)
        {
            WriteBuffer * wb = out_logs_buf.get();

            if (!out_logs_buf)
            {
                if (server_logs_file.empty())
                {
                    /// Use stderr by default
                    out_logs_buf = std::make_unique<WriteBufferFromFileDescriptor>(STDERR_FILENO);
                    wb = out_logs_buf.get();
                }
                else if (server_logs_file == "-")
                {
                    /// Use stdout if --server_logs_file=- specified
                    wb = &std_out;
                }
                else
                {
                    out_logs_buf = std::make_unique<WriteBufferFromFile>(server_logs_file, DBMS_DEFAULT_BUFFER_SIZE, O_WRONLY | O_APPEND | O_CREAT);
                    wb = out_logs_buf.get();
                }
            }

            logs_out_stream = std::make_shared<InternalTextLogsRowOutputStream>(*wb, stdout_is_a_tty);
            logs_out_stream->writePrefix();
        }
    }


    void onData(Block & block)
    {
        if (written_progress_chars)
            clearProgress();

        if (!block)
            return;

        processed_rows += block.rows();
        initBlockOutputStream(block);

        /// The header block containing zero rows was used to initialize block_out_stream, do not output it.
        if (block.rows() != 0)
        {
            block_out_stream->write(block);
            written_first_block = true;
        }

        /// Received data block is immediately displayed to the user.
        block_out_stream->flush();

        /// Restore progress bar after data block.
        writeProgress();
    }


    void onLogData(Block & block)
    {
        initLogsOutputStream();
        logs_out_stream->write(block);
        logs_out_stream->flush();
    }


    void onTotals(Block & block)
    {
        initBlockOutputStream(block);
        block_out_stream->setTotals(block);
    }

    void onExtremes(Block & block)
    {
        initBlockOutputStream(block);
        block_out_stream->setExtremes(block);
    }


    void onProgress(const Progress & value)
    {
        if (!progress.incrementPiecewiseAtomically(value))
        {
            // Just a keep-alive update.
            return;
        }
        if (block_out_stream)
            block_out_stream->onProgress(value);
        writeProgress();
    }


    void clearProgress()
    {
        written_progress_chars = 0;
        if (!send_logs)
            std::cerr << "\r" CLEAR_TO_END_OF_LINE;
    }


    void writeProgress()
    {
        if (!need_render_progress)
            return;

        /// Output all progress bar commands to stderr at once to avoid flicker.
        WriteBufferFromFileDescriptor message(STDERR_FILENO, 1024);

        static size_t increment = 0;
        static const char * indicators[8] =
        {
            "\033[1;30m→\033[0m",
            "\033[1;31m↘\033[0m",
            "\033[1;32m↓\033[0m",
            "\033[1;33m↙\033[0m",
            "\033[1;34m←\033[0m",
            "\033[1;35m↖\033[0m",
            "\033[1;36m↑\033[0m",
            "\033[1m↗\033[0m",
        };

        const char * indicator = indicators[increment % 8];

        if (!send_logs && written_progress_chars)
            message << '\r';

        size_t prefix_size = message.count();

        message << indicator << " Progress: ";

        message
            << formatReadableQuantity(progress.read_rows) << " rows, "
            << formatReadableSizeWithDecimalSuffix(progress.read_bytes);

        size_t elapsed_ns = watch.elapsed();
        if (elapsed_ns)
            message << " ("
                << formatReadableQuantity(progress.read_rows * 1000000000.0 / elapsed_ns) << " rows/s., "
                << formatReadableSizeWithDecimalSuffix(progress.read_bytes * 1000000000.0 / elapsed_ns) << "/s.) ";
        else
            message << ". ";

        written_progress_chars = message.count() - prefix_size - (strlen(indicator) - 2); /// Don't count invisible output (escape sequences).

        /// If the approximate number of rows to process is known, we can display a progress bar and percentage.
        if (progress.total_rows_to_read > 0)
        {
            size_t total_rows_corrected = std::max(progress.read_rows, progress.total_rows_to_read);

            /// To avoid flicker, display progress bar only if .5 seconds have passed since query execution start
            ///  and the query is less than halfway done.

            if (elapsed_ns > 500000000)
            {
                /// Trigger to start displaying progress bar. If query is mostly done, don't display it.
                if (progress.read_rows * 2 < total_rows_corrected)
                    show_progress_bar = true;

                if (show_progress_bar)
                {
                    ssize_t width_of_progress_bar = static_cast<ssize_t>(getTerminalWidth()) - written_progress_chars - strlen(" 99%");
                    if (width_of_progress_bar > 0)
                    {
                        std::string bar = UnicodeBar::render(UnicodeBar::getWidth(progress.read_rows, 0, total_rows_corrected, width_of_progress_bar));
                        message << "\033[0;32m" << bar << "\033[0m";
                        if (width_of_progress_bar > static_cast<ssize_t>(bar.size() / UNICODE_BAR_CHAR_SIZE))
                            message << std::string(width_of_progress_bar - bar.size() / UNICODE_BAR_CHAR_SIZE, ' ');
                    }
                }
            }

            /// Underestimate percentage a bit to avoid displaying 100%.
            message << ' ' << (99 * progress.read_rows / total_rows_corrected) << '%';
        }

        message << CLEAR_TO_END_OF_LINE;

        if (send_logs)
            message << '\n';

        ++increment;

        message.next();
    }


    void writeFinalProgress()
    {
        std::cout << "Processed "
            << formatReadableQuantity(progress.read_rows) << " rows, "
            << formatReadableSizeWithDecimalSuffix(progress.read_bytes);

        size_t elapsed_ns = watch.elapsed();
        if (elapsed_ns)
            std::cout << " ("
                << formatReadableQuantity(progress.read_rows * 1000000000.0 / elapsed_ns) << " rows/s., "
                << formatReadableSizeWithDecimalSuffix(progress.read_bytes * 1000000000.0 / elapsed_ns) << "/s.) ";
        else
            std::cout << ". ";
    }


    void onException(const Exception & e)
    {
        resetOutput();
        got_exception = true;

        actual_server_error = e.code();
        if (expected_server_error)
        {
            if (actual_server_error == expected_server_error)
                return;
            std::cerr << "Expected error code: " << expected_server_error << " but got: " << actual_server_error << "." << std::endl;
        }

        std::string text = e.displayText();

        auto embedded_stack_trace_pos = text.find("Stack trace");
        if (std::string::npos != embedded_stack_trace_pos && !config().getBool("stacktrace", false))
            text.resize(embedded_stack_trace_pos);

        /// If we probably have progress bar, we should add additional newline,
        /// otherwise exception may display concatenated with the progress bar.
        if (need_render_progress)
            std::cerr << '\n';

        std::cerr << "Received exception from server (version " << server_version << "):" << std::endl
            << "Code: " << e.code() << ". " << text << std::endl;
    }


    void onProfileInfo(const BlockStreamProfileInfo & profile_info)
    {
        if (profile_info.hasAppliedLimit() && block_out_stream)
            block_out_stream->setRowsBeforeLimit(profile_info.getRowsBeforeLimit());
    }


    void onEndOfStream()
    {
        if (block_out_stream)
            block_out_stream->writeSuffix();

        if (logs_out_stream)
            logs_out_stream->writeSuffix();

        resetOutput();

        if (is_interactive && !written_first_block)
        {
            if (written_progress_chars)
                clearProgress();
            std::cout << "Ok." << std::endl;
        }
    }

    static void showClientVersion()
    {
        std::cout << DBMS_NAME << " client version " << VERSION_STRING << VERSION_OFFICIAL << "." << std::endl;
    }

public:
    void init(int argc, char ** argv)
    {
        /// Don't parse options with Poco library. We need more sophisticated processing.
        stopOptionsProcessing();

        /** We allow different groups of arguments:
          * - common arguments;
          * - arguments for any number of external tables each in form "--external args...",
          *   where possible args are file, name, format, structure, types;
          * - param arguments for prepared statements.
          * Split these groups before processing.
          */
        using Arguments = std::vector<std::string>;

        Arguments common_arguments{""};        /// 0th argument is ignored.
        std::vector<Arguments> external_tables_arguments;

        bool in_external_group = false;
        for (int arg_num = 1; arg_num < argc; ++arg_num)
        {
            const char * arg = argv[arg_num];

            if (0 == strcmp(arg, "--external"))
            {
                in_external_group = true;
                external_tables_arguments.emplace_back(Arguments{""});
            }
            /// Options with value after equal sign.
            else if (in_external_group
                && (0 == strncmp(arg, "--file=", strlen("--file="))
                 || 0 == strncmp(arg, "--name=", strlen("--name="))
                 || 0 == strncmp(arg, "--format=", strlen("--format="))
                 || 0 == strncmp(arg, "--structure=", strlen("--structure="))
                 || 0 == strncmp(arg, "--types=", strlen("--types="))))
            {
                external_tables_arguments.back().emplace_back(arg);
            }
            /// Options with value after whitespace.
            else if (in_external_group
                && (0 == strcmp(arg, "--file")
                 || 0 == strcmp(arg, "--name")
                 || 0 == strcmp(arg, "--format")
                 || 0 == strcmp(arg, "--structure")
                 || 0 == strcmp(arg, "--types")))
            {
                if (arg_num + 1 < argc)
                {
                    external_tables_arguments.back().emplace_back(arg);
                    ++arg_num;
                    arg = argv[arg_num];
                    external_tables_arguments.back().emplace_back(arg);
                }
                else
                    break;
            }
            else
            {
                in_external_group = false;

                /// Parameter arg after underline.
                if (startsWith(arg, "--param_"))
                {
                    const char * param_continuation = arg + strlen("--param_");
                    const char * equal_pos = strchr(param_continuation, '=');

                    if (equal_pos == param_continuation)
                        throw Exception("Parameter name cannot be empty", ErrorCodes::BAD_ARGUMENTS);

                    if (equal_pos)
                    {
                        /// param_name=value
                        query_parameters.emplace(String(param_continuation, equal_pos), String(equal_pos + 1));
                    }
                    else
                    {
                        /// param_name value
                        ++arg_num;
                        arg = argv[arg_num];
                        query_parameters.emplace(String(param_continuation), String(arg));
                    }
                }
                else
                    common_arguments.emplace_back(arg);
            }
        }

        stdin_is_a_tty = isatty(STDIN_FILENO);
        stdout_is_a_tty = isatty(STDOUT_FILENO);

        uint64_t terminal_width = 0;
        if (stdin_is_a_tty)
            terminal_width = getTerminalWidth();

        namespace po = boost::program_options;

        /// Main commandline options related to client functionality and all parameters from Settings.
        po::options_description main_description = createOptionsDescription("Main options", terminal_width);
        main_description.add_options()
            ("help", "produce help message")
            ("config-file,C", po::value<std::string>(), "config-file path")
            ("config,c", po::value<std::string>(), "config-file path (another shorthand)")
            ("host,h", po::value<std::string>()->default_value("localhost"), "server host")
            ("port", po::value<int>()->default_value(9000), "server port")
            ("secure,s", "Use TLS connection")
            ("user,u", po::value<std::string>()->default_value("default"), "user")
            /** If "--password [value]" is used but the value is omitted, the bad argument exception will be thrown.
              * implicit_value is used to avoid this exception (to allow user to type just "--password")
              * Since currently boost provides no way to check if a value has been set implicitly for an option,
              * the "\n" is used to distinguish this case because there is hardly a chance an user would use "\n"
              * as the password.
              */
            ("password", po::value<std::string>()->implicit_value("\n", ""), "password")
            ("ask-password", "ask-password")
            ("quota_key", po::value<std::string>(), "A string to differentiate quotas when the user have keyed quotas configured on server")
            ("query_id", po::value<std::string>(), "query_id")
            ("query,q", po::value<std::string>(), "query")
            ("database,d", po::value<std::string>(), "database")
            ("pager", po::value<std::string>(), "pager")
            ("disable_suggestion,A", "Disable loading suggestion data. Note that suggestion data is loaded asynchronously through a second connection to ClickHouse server. Also it is reasonable to disable suggestion if you want to paste a query with TAB characters. Shorthand option -A is for those who get used to mysql client.")
            ("suggestion_limit", po::value<int>()->default_value(10000),
                "Suggestion limit for how many databases, tables and columns to fetch.")
            ("multiline,m", "multiline")
            ("multiquery,n", "multiquery")
            ("format,f", po::value<std::string>(), "default output format")
            ("testmode,T", "enable test hints in comments")
            ("ignore-error", "do not stop processing in multiquery mode")
            ("vertical,E", "vertical output format, same as --format=Vertical or FORMAT Vertical or \\G at end of command")
            ("time,t", "print query execution time to stderr in non-interactive mode (for benchmarks)")
            ("stacktrace", "print stack traces of exceptions")
            ("progress", "print progress even in non-interactive mode")
            ("version,V", "print version information and exit")
            ("version-clean", "print version in machine-readable format and exit")
            ("echo", "in batch mode, print query before execution")
            ("max_client_network_bandwidth", po::value<int>(), "the maximum speed of data exchange over the network for the client in bytes per second.")
            ("compression", po::value<bool>(), "enable or disable compression")
            ("log-level", po::value<std::string>(), "client log level")
            ("server_logs_file", po::value<std::string>(), "put server logs into specified file")
        ;

        Settings cmd_settings;
        cmd_settings.addProgramOptions(main_description);

        /// Commandline options related to external tables.
        po::options_description external_description = createOptionsDescription("External tables options", terminal_width);
        external_description.add_options()
            ("file", po::value<std::string>(), "data file or - for stdin")
            ("name", po::value<std::string>()->default_value("_data"), "name of the table")
            ("format", po::value<std::string>()->default_value("TabSeparated"), "data format")
            ("structure", po::value<std::string>(), "structure")
            ("types", po::value<std::string>(), "types")
        ;

        /// Parse main commandline options.
        po::parsed_options parsed = po::command_line_parser(common_arguments).options(main_description).run();
        po::variables_map options;
        po::store(parsed, options);
        po::notify(options);

        if (options.count("version") || options.count("V"))
        {
            showClientVersion();
            exit(0);
        }

        if (options.count("version-clean"))
        {
            std::cout << VERSION_STRING;
            exit(0);
        }

        /// Output of help message.
        if (options.count("help")
            || (options.count("host") && options["host"].as<std::string>() == "elp"))    /// If user writes -help instead of --help.
        {
            std::cout << main_description << "\n";
            std::cout << external_description << "\n";
            std::cout << "In addition, --param_name=value can be specified for substitution of parameters for parametrized queries.\n";
            exit(0);
        }

        if (options.count("log-level"))
            Poco::Logger::root().setLevel(options["log-level"].as<std::string>());

        size_t number_of_external_tables_with_stdin_source = 0;
        for (size_t i = 0; i < external_tables_arguments.size(); ++i)
        {
            /// Parse commandline options related to external tables.
            po::parsed_options parsed_tables = po::command_line_parser(external_tables_arguments[i]).options(external_description).run();
            po::variables_map external_options;
            po::store(parsed_tables, external_options);

            try
            {
                external_tables.emplace_back(external_options);
                if (external_tables.back().file == "-")
                    ++number_of_external_tables_with_stdin_source;
                if (number_of_external_tables_with_stdin_source > 1)
                    throw Exception("Two or more external tables has stdin (-) set as --file field", ErrorCodes::BAD_ARGUMENTS);
            }
            catch (const Exception & e)
            {
                std::string text = e.displayText();
                std::cerr << "Code: " << e.code() << ". " << text << std::endl;
                std::cerr << "Table №" << i << std::endl << std::endl;
                exit(e.code());
            }
        }

        context.makeGlobalContext();
        context.setSettings(cmd_settings);

        /// Copy settings-related program options to config.
        /// TODO: Is this code necessary?
        for (const auto & setting : context.getSettingsRef())
        {
            const String name = setting.getName().toString();
            if (options.count(name))
                config().setString(name, options[name].as<std::string>());
        }

        if (options.count("config-file") && options.count("config"))
            throw Exception("Two or more configuration files referenced in arguments", ErrorCodes::BAD_ARGUMENTS);

        /// Save received data into the internal config.
        if (options.count("config-file"))
            config().setString("config-file", options["config-file"].as<std::string>());
        if (options.count("config"))
            config().setString("config-file", options["config"].as<std::string>());
        if (options.count("host") && !options["host"].defaulted())
            config().setString("host", options["host"].as<std::string>());
        if (options.count("query_id"))
            config().setString("query_id", options["query_id"].as<std::string>());
        if (options.count("query"))
            config().setString("query", options["query"].as<std::string>());
        if (options.count("database"))
            config().setString("database", options["database"].as<std::string>());
        if (options.count("pager"))
            config().setString("pager", options["pager"].as<std::string>());

        if (options.count("port") && !options["port"].defaulted())
            config().setInt("port", options["port"].as<int>());
        if (options.count("secure"))
            config().setBool("secure", true);
        if (options.count("user") && !options["user"].defaulted())
            config().setString("user", options["user"].as<std::string>());
        if (options.count("password"))
            config().setString("password", options["password"].as<std::string>());
        if (options.count("ask-password"))
            config().setBool("ask-password", true);
        if (options.count("quota_key"))
            config().setString("quota_key", options["quota_key"].as<std::string>());
        if (options.count("multiline"))
            config().setBool("multiline", true);
        if (options.count("multiquery"))
            config().setBool("multiquery", true);
        if (options.count("testmode"))
            config().setBool("testmode", true);
        if (options.count("ignore-error"))
            config().setBool("ignore-error", true);
        if (options.count("format"))
            config().setString("format", options["format"].as<std::string>());
        if (options.count("vertical"))
            config().setBool("vertical", true);
        if (options.count("stacktrace"))
            config().setBool("stacktrace", true);
        if (options.count("progress"))
            config().setBool("progress", true);
        if (options.count("echo"))
            config().setBool("echo", true);
        if (options.count("time"))
            print_time_to_stderr = true;
        if (options.count("max_client_network_bandwidth"))
            max_client_network_bandwidth = options["max_client_network_bandwidth"].as<int>();
        if (options.count("compression"))
            config().setBool("compression", options["compression"].as<bool>());
        if (options.count("server_logs_file"))
            server_logs_file = options["server_logs_file"].as<std::string>();
        if (options.count("disable_suggestion"))
            config().setBool("disable_suggestion", true);
        if (options.count("suggestion_limit"))
            config().setInt("suggestion_limit", options["suggestion_limit"].as<int>());

        argsToConfig(common_arguments, config(), 100);

    }
};

}

#pragma GCC diagnostic ignored "-Wunused-function"
#pragma GCC diagnostic ignored "-Wmissing-declarations"

int mainEntryClickHouseClient(int argc, char ** argv)
{
    try
    {
        DB::Client client;
        client.init(argc, argv);
        return client.run();
    }
    catch (const boost::program_options::error & e)
    {
        std::cerr << "Bad arguments: " << e.what() << std::endl;
        return 1;
    }
    catch (...)
    {
        std::cerr << DB::getCurrentExceptionMessage(true) << std::endl;
        return 1;
    }
}