ClickHouse/dbms/src/Dictionaries/FileDictionarySource.h

#pragma once

#include <Dictionaries/IDictionarySource.h>
#include <Poco/Timestamp.h>


namespace DB
{

class Context;


/// Allows loading dictionaries from a file with given format, does not support "random access"
class FileDictionarySource final : public IDictionarySource
{
public:
    FileDictionarySource(const std::string & filename, const std::string & format, Block & sample_block,
        const Context & context);

    FileDictionarySource(const FileDictionarySource & other);

    BlockInputStreamPtr loadAll() override;

    BlockInputStreamPtr loadIds(const std::vector<UInt64> & ids) override
    {
        throw Exception{"Method loadIds is unsupported for FileDictionarySource", ErrorCodes::NOT_IMPLEMENTED};
    }

    BlockInputStreamPtr loadKeys(
        const ConstColumnPlainPtrs & key_columns, const std::vector<std::size_t> & requested_rows) override
    {
        throw Exception{"Method loadKeys is unsupported for FileDictionarySource", ErrorCodes::NOT_IMPLEMENTED};
    }

    bool isModified() const override { return getLastModification() > last_modification; }
    bool supportsSelectiveLoad() const override { return false; }

    DictionarySourcePtr clone() const override { return std::make_unique<FileDictionarySource>(*this); }

    std::string toString() const override;

private:
    Poco::Timestamp getLastModification() const;

    const std::string filename;
    const std::string format;
    Block sample_block;
    const Context & context;
    Poco::Timestamp last_modification;
};

}