ClickHouse/src/Parsers/ParserExplainQuery.cpp

#include <Parsers/ParserExplainQuery.h>

#include <Parsers/ASTExplainQuery.h>
#include <Parsers/CommonParsers.h>
#include <Parsers/ParserCreateQuery.h>
#include <Parsers/ParserSelectWithUnionQuery.h>
#include <Parsers/ParserInsertQuery.h>
#include <Parsers/ParserSetQuery.h>
#include <Parsers/ParserQuery.h>
#include <Parsers/ParserSystemQuery.h>

namespace DB
{

bool ParserExplainQuery::parseImpl(Pos & pos, ASTPtr & node, Expected & expected)
{
    ASTExplainQuery::ExplainKind kind;

    ParserKeyword s_ast("AST");
    ParserKeyword s_explain("EXPLAIN");
    ParserKeyword s_syntax("SYNTAX");
    ParserKeyword s_query_tree("QUERY TREE");
    ParserKeyword s_pipeline("PIPELINE");
    ParserKeyword s_plan("PLAN");
    ParserKeyword s_estimates("ESTIMATE");
    ParserKeyword s_table_override("TABLE OVERRIDE");
    ParserKeyword s_current_transaction("CURRENT TRANSACTION");

    if (s_explain.ignore(pos, expected))
    {
        kind = ASTExplainQuery::QueryPlan;

        if (s_ast.ignore(pos, expected))
            kind = ASTExplainQuery::ExplainKind::ParsedAST;
        else if (s_syntax.ignore(pos, expected))
            kind = ASTExplainQuery::ExplainKind::AnalyzedSyntax;
        else if (s_query_tree.ignore(pos, expected))
            kind = ASTExplainQuery::ExplainKind::QueryTree;
        else if (s_pipeline.ignore(pos, expected))
            kind = ASTExplainQuery::ExplainKind::QueryPipeline;
        else if (s_plan.ignore(pos, expected))
            kind = ASTExplainQuery::ExplainKind::QueryPlan;
        else if (s_estimates.ignore(pos, expected))
            kind = ASTExplainQuery::ExplainKind::QueryEstimates;
        else if (s_table_override.ignore(pos, expected))
            kind = ASTExplainQuery::ExplainKind::TableOverride;
        else if (s_current_transaction.ignore(pos, expected))
            kind = ASTExplainQuery::ExplainKind::CurrentTransaction;
    }
    else
        return false;

    auto explain_query = std::make_shared<ASTExplainQuery>(kind);

    {
        ASTPtr settings;
        ParserSetQuery parser_settings(true);

        auto begin = pos;
        if (parser_settings.parse(pos, settings, expected))
            explain_query->setSettings(std::move(settings));
        else
            pos = begin;
    }

    ParserCreateTableQuery create_p;
    ParserSelectWithUnionQuery select_p;
    ParserInsertQuery insert_p(end, allow_settings_after_format_in_insert);
    ParserSystemQuery system_p;
    ASTPtr query;
    if (kind == ASTExplainQuery::ExplainKind::ParsedAST)
    {
        ParserQuery p(end, allow_settings_after_format_in_insert);
        if (p.parse(pos, query, expected))
            explain_query->setExplainedQuery(std::move(query));
        else
            return false;
    }
    else if (kind == ASTExplainQuery::ExplainKind::TableOverride)
    {
        ASTPtr table_function;
        if (!ParserFunction(true, true).parse(pos, table_function, expected))
            return false;
        ASTPtr table_override;
        if (!ParserTableOverrideDeclaration(false).parse(pos, table_override, expected))
            return false;
        explain_query->setTableFunction(table_function);
        explain_query->setTableOverride(table_override);
    }
    else if (kind == ASTExplainQuery::ExplainKind::QueryTree)
    {
        if (select_p.parse(pos, query, expected))
            explain_query->setExplainedQuery(std::move(query));
        else
            return false;
    }
    else if (kind == ASTExplainQuery::ExplainKind::CurrentTransaction)
    {
        /// Nothing to parse
    }
    else if (select_only)
    {
        if (select_p.parse(pos, query, expected))
            explain_query->setExplainedQuery(std::move(query));
        else
            return false;
    }
    else if (select_p.parse(pos, query, expected) ||
        create_p.parse(pos, query, expected) ||
        insert_p.parse(pos, query, expected) ||
        system_p.parse(pos, query, expected))
    {
        explain_query->setExplainedQuery(std::move(query));
    }
    else
    {
        return false;
    }

    node = std::move(explain_query);
    return true;
}

}