ClickHouse/dbms/src/DataStreams/AddingDefaultBlockInputStream.h

#pragma once

#include <DataStreams/IProfilingBlockInputStream.h>
#include <Interpreters/evaluateMissingDefaults.h>
#include <Columns/ColumnConst.h>
#include <Interpreters/Context.h>
#include <Storages/ColumnDefault.h>


namespace DB
{


/** Adds missing columns to the block with default values.
  * These columns are materialized (not constants).
  */
class AddingDefaultBlockInputStream : public IProfilingBlockInputStream
{
public:
    AddingDefaultBlockInputStream(
        BlockInputStreamPtr input_,
        NamesAndTypesListPtr required_columns_,
        const ColumnDefaults & column_defaults_,
        const Context & context_)
        : required_columns(required_columns_),
          column_defaults(column_defaults_), context(context_)
    {
        children.push_back(input_);
    }

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

    String getID() const override
    {
        std::stringstream res;
        res << "AddingDefault(" << children.back()->getID();

        for (NamesAndTypesList::const_iterator it = required_columns->begin(); it != required_columns->end(); ++it)
            res << ", " << it->name << ", " << it->type->getName();

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

protected:
    Block readImpl() override
    {
        Block res = children.back()->read();
        if (!res)
            return res;
        /** @todo if somehow block does not contain values for implicitly-defaulted columns that are prerequisites
         *    for explicitly-defaulted ones, exception will be thrown during evaluating such columns
         *    (implicitly-defaulted columns are evaluated on the line after following one. */
        evaluateMissingDefaults(res, *required_columns, column_defaults, context);
        res.addDefaults(*required_columns);
        return res;
    }

private:
    NamesAndTypesListPtr required_columns;
    const ColumnDefaults column_defaults;
    Context context;
};

}