ClickHouse/src/Parsers/ParserSelectQuery.cpp

#include <memory>
#include <Parsers/ASTSelectQuery.h>
#include <Parsers/IParserBase.h>
#include <Parsers/CommonParsers.h>
#include <Parsers/ExpressionElementParsers.h>
#include <Parsers/ExpressionListParsers.h>
#include <Parsers/ParserSetQuery.h>
#include <Parsers/ParserSampleRatio.h>
#include <Parsers/ParserSelectQuery.h>
#include <Parsers/ParserTablesInSelectQuery.h>
#include <Parsers/ParserWithElement.h>


namespace DB
{

namespace ErrorCodes
{
    extern const int TOP_AND_LIMIT_TOGETHER;
    extern const int WITH_TIES_WITHOUT_ORDER_BY;
    extern const int LIMIT_BY_WITH_TIES_IS_NOT_SUPPORTED;
    extern const int ROW_AND_ROWS_TOGETHER;
    extern const int FIRST_AND_NEXT_TOGETHER;
}


bool ParserSelectQuery::parseImpl(Pos & pos, ASTPtr & node, Expected & expected)
{
    auto select_query = std::make_shared<ASTSelectQuery>();
    node = select_query;

    ParserKeyword s_select("SELECT");
    ParserKeyword s_distinct("DISTINCT");
    ParserKeyword s_from("FROM");
    ParserKeyword s_prewhere("PREWHERE");
    ParserKeyword s_where("WHERE");
    ParserKeyword s_group_by("GROUP BY");
    ParserKeyword s_with("WITH");
    ParserKeyword s_totals("TOTALS");
    ParserKeyword s_having("HAVING");
    ParserKeyword s_order_by("ORDER BY");
    ParserKeyword s_limit("LIMIT");
    ParserKeyword s_settings("SETTINGS");
    ParserKeyword s_by("BY");
    ParserKeyword s_rollup("ROLLUP");
    ParserKeyword s_cube("CUBE");
    ParserKeyword s_top("TOP");
    ParserKeyword s_with_ties("WITH TIES");
    ParserKeyword s_offset("OFFSET");
    ParserKeyword s_fetch("FETCH");
    ParserKeyword s_only("ONLY");
    ParserKeyword s_row("ROW");
    ParserKeyword s_rows("ROWS");
    ParserKeyword s_first("FIRST");
    ParserKeyword s_next("NEXT");

    ParserNotEmptyExpressionList exp_list(false);
    ParserNotEmptyExpressionList exp_list_for_with_clause(false);
    ParserNotEmptyExpressionList exp_list_for_select_clause(true);    /// Allows aliases without AS keyword.
    ParserExpressionWithOptionalAlias exp_elem(false);
    ParserOrderByExpressionList order_list;

    ParserToken open_bracket(TokenType::OpeningRoundBracket);
    ParserToken close_bracket(TokenType::ClosingRoundBracket);

    ASTPtr with_expression_list;
    ASTPtr select_expression_list;
    ASTPtr tables;
    ASTPtr prewhere_expression;
    ASTPtr where_expression;
    ASTPtr group_expression_list;
    ASTPtr having_expression;
    ASTPtr order_expression_list;
    ASTPtr limit_by_length;
    ASTPtr limit_by_offset;
    ASTPtr limit_by_expression_list;
    ASTPtr limit_offset;
    ASTPtr limit_length;
    ASTPtr top_length;
    ASTPtr settings;

    /// WITH expr list
    {
        if (s_with.ignore(pos, expected))
        {
            if (!ParserList(std::make_unique<ParserWithElement>(), std::make_unique<ParserToken>(TokenType::Comma))
                     .parse(pos, with_expression_list, expected))
                return false;
            if (with_expression_list->children.empty())
                return false;
        }
    }

    /// SELECT [DISTINCT] [TOP N [WITH TIES]] expr list
    {
        if (!s_select.ignore(pos, expected))
            return false;

        if (s_distinct.ignore(pos, expected))
            select_query->distinct = true;

        if (s_top.ignore(pos, expected))
        {
            ParserNumber num;

            if (open_bracket.ignore(pos, expected))
            {
                if (!num.parse(pos, top_length, expected))
                    return false;
                if (!close_bracket.ignore(pos, expected))
                    return false;
            }
            else
            {
                if (!num.parse(pos, top_length, expected))
                    return false;
            }

            if (s_with_ties.ignore(pos, expected))
                select_query->limit_with_ties = true;
        }

        if (!exp_list_for_select_clause.parse(pos, select_expression_list, expected))
            return false;
    }

    /// FROM database.table or FROM table or FROM (subquery) or FROM tableFunction(...)
    if (s_from.ignore(pos, expected))
    {
        if (!ParserTablesInSelectQuery().parse(pos, tables, expected))
            return false;
    }

    /// PREWHERE expr
    if (s_prewhere.ignore(pos, expected))
    {
        if (!exp_elem.parse(pos, prewhere_expression, expected))
            return false;
    }

    /// WHERE expr
    if (s_where.ignore(pos, expected))
    {
        if (!exp_elem.parse(pos, where_expression, expected))
            return false;
    }

    /// GROUP BY expr list
    if (s_group_by.ignore(pos, expected))
    {
        if (s_rollup.ignore(pos, expected))
            select_query->group_by_with_rollup = true;
        else if (s_cube.ignore(pos, expected))
            select_query->group_by_with_cube = true;

        if ((select_query->group_by_with_rollup || select_query->group_by_with_cube) && !open_bracket.ignore(pos, expected))
            return false;

        if (!exp_list.parse(pos, group_expression_list, expected))
            return false;

        if ((select_query->group_by_with_rollup || select_query->group_by_with_cube) && !close_bracket.ignore(pos, expected))
            return false;
    }

    /// WITH ROLLUP, CUBE or TOTALS
    if (s_with.ignore(pos, expected))
    {
        if (s_rollup.ignore(pos, expected))
            select_query->group_by_with_rollup = true;
        else if (s_cube.ignore(pos, expected))
            select_query->group_by_with_cube = true;
        else if (s_totals.ignore(pos, expected))
            select_query->group_by_with_totals = true;
        else
            return false;
    }

    /// WITH TOTALS
    if (s_with.ignore(pos, expected))
    {
        if (select_query->group_by_with_totals || !s_totals.ignore(pos, expected))
            return false;

        select_query->group_by_with_totals = true;
    }

    /// HAVING expr
    if (s_having.ignore(pos, expected))
    {
        if (!exp_elem.parse(pos, having_expression, expected))
            return false;
    }

    /// ORDER BY expr ASC|DESC COLLATE 'locale' list
    if (s_order_by.ignore(pos, expected))
    {
        if (!order_list.parse(pos, order_expression_list, expected))
            return false;
    }

    /// This is needed for TOP expression, because it can also use WITH TIES.
    bool limit_with_ties_occured = false;

    /// LIMIT length | LIMIT offset, length | LIMIT count BY expr-list | LIMIT offset, length BY expr-list
    if (s_limit.ignore(pos, expected))
    {
        ParserToken s_comma(TokenType::Comma);

        if (!exp_elem.parse(pos, limit_length, expected))
            return false;

        if (s_comma.ignore(pos, expected))
        {
            limit_offset = limit_length;
            if (!exp_elem.parse(pos, limit_length, expected))
                return false;

            if (s_with_ties.ignore(pos, expected))
            {
                limit_with_ties_occured = true;
                select_query->limit_with_ties = true;
            }
        }
        else if (s_offset.ignore(pos, expected))
        {
            if (!exp_elem.parse(pos, limit_offset, expected))
                return false;
        }
        else if (s_with_ties.ignore(pos, expected))
        {
            limit_with_ties_occured = true;
            select_query->limit_with_ties = true;
        }

        if (s_by.ignore(pos, expected))
        {
            /// WITH TIES was used alongside LIMIT BY
            /// But there are other kind of queries like LIMIT n BY smth LIMIT m WITH TIES which are allowed.
            /// So we have to ignore WITH TIES exactly in LIMIT BY state.
            if (limit_with_ties_occured)
                throw Exception("Can not use WITH TIES alongside LIMIT BY", ErrorCodes::LIMIT_BY_WITH_TIES_IS_NOT_SUPPORTED);

            limit_by_length = limit_length;
            limit_by_offset = limit_offset;
            limit_length = nullptr;
            limit_offset = nullptr;

            if (!exp_list.parse(pos, limit_by_expression_list, expected))
                return false;
        }

        if (top_length && limit_length)
            throw Exception("Can not use TOP and LIMIT together", ErrorCodes::TOP_AND_LIMIT_TOGETHER);
    }
    else if (s_offset.ignore(pos, expected))
    {
        /// OFFSET offset_row_count {ROW | ROWS} FETCH {FIRST | NEXT} fetch_row_count {ROW | ROWS} {ONLY | WITH TIES}
        bool offset_with_fetch_maybe = false;

        if (!exp_elem.parse(pos, limit_offset, expected))
            return false;

        if (s_row.ignore(pos, expected))
        {
            if (s_rows.ignore(pos, expected))
                throw Exception("Can not use ROW and ROWS together", ErrorCodes::ROW_AND_ROWS_TOGETHER);
            offset_with_fetch_maybe = true;
        }
        else if (s_rows.ignore(pos, expected))
        {
            offset_with_fetch_maybe = true;
        }

        if (offset_with_fetch_maybe && s_fetch.ignore(pos, expected))
        {
            /// OFFSET FETCH clause must exists with "ORDER BY"
            if (!order_expression_list)
                return false;

            if (s_first.ignore(pos, expected))
            {
                if (s_next.ignore(pos, expected))
                    throw Exception("Can not use FIRST and NEXT together", ErrorCodes::FIRST_AND_NEXT_TOGETHER);
            }
            else if (!s_next.ignore(pos, expected))
                return false;

            if (!exp_elem.parse(pos, limit_length, expected))
                return false;

            if (s_row.ignore(pos, expected))
            {
                if (s_rows.ignore(pos, expected))
                    throw Exception("Can not use ROW and ROWS together", ErrorCodes::ROW_AND_ROWS_TOGETHER);
            }
            else if (!s_rows.ignore(pos, expected))
                return false;

            if (s_with_ties.ignore(pos, expected))
            {
                select_query->limit_with_ties = true;
            }
            else if (s_only.ignore(pos, expected))
            {
                select_query->limit_with_ties = false;
            }
            else
            {
                return false;
            }
        }
    }

    /// Because TOP n in totally equals LIMIT n
    if (top_length)
        limit_length = top_length;

    /// LIMIT length [WITH TIES] | LIMIT offset, length [WITH TIES]
    if (s_limit.ignore(pos, expected))
    {
        if (!limit_by_length || limit_length)
            return false;

        ParserToken s_comma(TokenType::Comma);

        if (!exp_elem.parse(pos, limit_length, expected))
            return false;

        if (s_comma.ignore(pos, expected))
        {
            limit_offset = limit_length;
            if (!exp_elem.parse(pos, limit_length, expected))
                return false;
        }
        else if (s_offset.ignore(pos, expected))
        {
            if (!exp_elem.parse(pos, limit_offset, expected))
                return false;
        }

        if (s_with_ties.ignore(pos, expected))
            select_query->limit_with_ties = true;
    }

    /// WITH TIES was used without ORDER BY
    if (!order_expression_list && select_query->limit_with_ties)
        throw Exception("Can not use WITH TIES without ORDER BY", ErrorCodes::WITH_TIES_WITHOUT_ORDER_BY);

    /// SETTINGS key1 = value1, key2 = value2, ...
    if (s_settings.ignore(pos, expected))
    {
        ParserSetQuery parser_settings(true);

        if (!parser_settings.parse(pos, settings, expected))
            return false;
    }

    select_query->setExpression(ASTSelectQuery::Expression::WITH, std::move(with_expression_list));
    select_query->setExpression(ASTSelectQuery::Expression::SELECT, std::move(select_expression_list));
    select_query->setExpression(ASTSelectQuery::Expression::TABLES, std::move(tables));
    select_query->setExpression(ASTSelectQuery::Expression::PREWHERE, std::move(prewhere_expression));
    select_query->setExpression(ASTSelectQuery::Expression::WHERE, std::move(where_expression));
    select_query->setExpression(ASTSelectQuery::Expression::GROUP_BY, std::move(group_expression_list));
    select_query->setExpression(ASTSelectQuery::Expression::HAVING, std::move(having_expression));
    select_query->setExpression(ASTSelectQuery::Expression::ORDER_BY, std::move(order_expression_list));
    select_query->setExpression(ASTSelectQuery::Expression::LIMIT_BY_OFFSET, std::move(limit_by_offset));
    select_query->setExpression(ASTSelectQuery::Expression::LIMIT_BY_LENGTH, std::move(limit_by_length));
    select_query->setExpression(ASTSelectQuery::Expression::LIMIT_BY, std::move(limit_by_expression_list));
    select_query->setExpression(ASTSelectQuery::Expression::LIMIT_OFFSET, std::move(limit_offset));
    select_query->setExpression(ASTSelectQuery::Expression::LIMIT_LENGTH, std::move(limit_length));
    select_query->setExpression(ASTSelectQuery::Expression::SETTINGS, std::move(settings));
    return true;
}

}