ClickHouse/src/Interpreters/InterpreterSelectWithUnionQuery.h

#pragma once

#include <Core/QueryProcessingStage.h>
#include <Interpreters/IInterpreterUnionOrSelectQuery.h>

namespace DB
{

class InterpreterSelectQuery;
class QueryPlan;

/** Interprets one or multiple SELECT queries inside UNION/UNION ALL/UNION DISTINCT chain.
  */
class InterpreterSelectWithUnionQuery : public IInterpreterUnionOrSelectQuery
{
public:
    using IInterpreterUnionOrSelectQuery::getSampleBlock;

    InterpreterSelectWithUnionQuery(
        const ASTPtr & query_ptr_,
        ContextPtr context_,
        const SelectQueryOptions &,
        const Names & required_result_column_names = {});

    ~InterpreterSelectWithUnionQuery() override;

    /// Builds QueryPlan for current query.
    virtual void buildQueryPlan(QueryPlan & query_plan) override;

    BlockIO execute() override;

    bool ignoreLimits() const override { return options.ignore_limits; }
    bool ignoreQuota() const override { return options.ignore_quota; }

    static Block getSampleBlock(
        const ASTPtr & query_ptr_,
        ContextPtr context_,
        bool is_subquery = false);

    virtual void ignoreWithTotals() override;

private:
    std::vector<std::unique_ptr<IInterpreterUnionOrSelectQuery>> nested_interpreters;

    static Block getCommonHeaderForUnion(const Blocks & headers);

    Block getCurrentChildResultHeader(const ASTPtr & ast_ptr_, const Names & required_result_column_names);

    std::unique_ptr<IInterpreterUnionOrSelectQuery>
    buildCurrentChildInterpreter(const ASTPtr & ast_ptr_, const Names & current_required_result_column_names);
};

}