ClickHouse/dbms/src/DataStreams/CreatingSetsBlockInputStream.h

#pragma once

#include <Poco/Logger.h>
#include <DataStreams/IProfilingBlockInputStream.h>
#include <Interpreters/ExpressionAnalyzer.h>    /// SubqueriesForSets


namespace Poco { class Logger; }

namespace DB
{

/** Returns the data from the stream of blocks without changes, but
  * in the `readPrefix` function or before reading the first block
  * initializes all the passed sets.
  */
class CreatingSetsBlockInputStream : public IProfilingBlockInputStream
{
public:
    CreatingSetsBlockInputStream(
        const BlockInputStreamPtr & input,
        const SubqueriesForSets & subqueries_for_sets_,
        const Limits & limits)
        : subqueries_for_sets(subqueries_for_sets_),
        max_rows_to_transfer(limits.max_rows_to_transfer),
        max_bytes_to_transfer(limits.max_bytes_to_transfer),
        transfer_overflow_mode(limits.transfer_overflow_mode)
    {
        for (auto & elem : subqueries_for_sets)
            if (elem.second.source)
                children.push_back(elem.second.source);

        children.push_back(input);
    }

    String getName() const override { return "CreatingSets"; }

    String getID() const override
    {
        std::stringstream res;
        res << "CreatingSets(";

        Strings children_ids(children.size());
        for (size_t i = 0; i < children.size(); ++i)
            children_ids[i] = children[i]->getID();

        /// Let's assume that the order of creating sets does not matter.
        std::sort(children_ids.begin(), children_ids.end() - 1);

        for (size_t i = 0; i < children_ids.size(); ++i)
            res << (i == 0 ? "" : ", ") << children_ids[i];

        res << ")";
        return res.str();
    }

    /// Takes `totals` only from the main source, not from subquery sources.
    const Block & getTotals() override;

protected:
    Block readImpl() override;
    void readPrefixImpl() override;

private:
    SubqueriesForSets subqueries_for_sets;
    bool created = false;

    size_t max_rows_to_transfer;
    size_t max_bytes_to_transfer;
    OverflowMode transfer_overflow_mode;

    size_t rows_to_transfer = 0;
    size_t bytes_to_transfer = 0;

    using Logger = Poco::Logger;
    Logger * log = &Logger::get("CreatingSetsBlockInputStream");

    void createAll();
    void createOne(SubqueryForSet & subquery);
};

}