ClickHouse/dbms/src/Storages/StorageHDFS.cpp

#include <Common/config.h>

#if USE_HDFS

#include <Storages/StorageFactory.h>
#include <Storages/StorageHDFS.h>
#include <Interpreters/Context.h>
#include <Interpreters/evaluateConstantExpression.h>
#include <Parsers/ASTLiteral.h>
#include <IO/ReadBufferFromHDFS.h>
#include <IO/WriteBufferFromHDFS.h>
#include <Formats/FormatFactory.h>
#include <DataStreams/IBlockOutputStream.h>
#include <DataStreams/UnionBlockInputStream.h>
#include <DataStreams/IBlockInputStream.h>
#include <DataStreams/OwningBlockInputStream.h>


namespace DB
{
namespace ErrorCodes
{
    extern const int NUMBER_OF_ARGUMENTS_DOESNT_MATCH;
    extern const int NOT_IMPLEMENTED;
    extern const int BAD_ARGUMENTS;
}

StorageHDFS::StorageHDFS(const String & uri_,
    const std::string & database_name_,
    const std::string & table_name_,
    const String & format_name_,
    const ColumnsDescription & columns_,
    Context & context_)
    : IStorage(columns_)
    , uri(uri_)
    , format_name(format_name_)
    , table_name(table_name_)
    , database_name(database_name_)
    , context(context_)
{
}

namespace
{

class HDFSBlockInputStream : public IBlockInputStream
{
public:
    HDFSBlockInputStream(const String & uri,
        const String & format,
        const Block & sample_block,
        const Context & context,
        UInt64 max_block_size)
    {
        std::unique_ptr<ReadBuffer> read_buf = std::make_unique<ReadBufferFromHDFS>(uri);
        auto input_stream = FormatFactory::instance().getInput(format, *read_buf, sample_block, context, max_block_size);
        reader = std::make_shared<OwningBlockInputStream<ReadBuffer>>(input_stream, std::move(read_buf));
    }

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

    Block readImpl() override
    {
        return reader->read();
    }

    Block getHeader() const override
    {
        return reader->getHeader();
    }

    void readPrefixImpl() override
    {
        reader->readPrefix();
    }

    void readSuffixImpl() override
    {
        reader->readSuffix();
    }

private:
    BlockInputStreamPtr reader;
};

class HDFSBlockOutputStream : public IBlockOutputStream
{
public:
    HDFSBlockOutputStream(const String & uri,
        const String & format,
        const Block & sample_block_,
        const Context & context)
        : sample_block(sample_block_)
    {
        write_buf = std::make_unique<WriteBufferFromHDFS>(uri);
        writer = FormatFactory::instance().getOutput(format, *write_buf, sample_block, context);
    }

    Block getHeader() const override
    {
        return sample_block;
    }

    void write(const Block & block) override
    {
        writer->write(block);
    }

    void writePrefix() override
    {
        writer->writePrefix();
    }

    void writeSuffix() override
    {
        writer->writeSuffix();
        writer->flush();
        write_buf->sync();
    }

private:
    Block sample_block;
    std::unique_ptr<WriteBufferFromHDFS> write_buf;
    BlockOutputStreamPtr writer;
};

}


BlockInputStreams StorageHDFS::read(
    const Names & /*column_names*/,
    const SelectQueryInfo & /*query_info*/,
    const Context & context_,
    QueryProcessingStage::Enum  /*processed_stage*/,
    size_t max_block_size,
    unsigned /*num_streams*/)
{
    return {std::make_shared<HDFSBlockInputStream>(
        uri,
        format_name,
        getSampleBlock(),
        context_,
        max_block_size)};
}

void StorageHDFS::rename(const String & /*new_path_to_db*/, const String & new_database_name, const String & new_table_name)
{
    table_name = new_table_name;
    database_name = new_database_name;
}

BlockOutputStreamPtr StorageHDFS::write(const ASTPtr & /*query*/, const Context & /*context*/)
{
    return std::make_shared<HDFSBlockOutputStream>(uri, format_name, getSampleBlock(), context);
}

void registerStorageHDFS(StorageFactory & factory)
{
    factory.registerStorage("HDFS", [](const StorageFactory::Arguments & args)
    {
        ASTs & engine_args = args.engine_args;

        if (!(engine_args.size() == 1 || engine_args.size() == 2))
            throw Exception(
                "Storage HDFS requires exactly 2 arguments: url and name of used format.", ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);

        engine_args[0] = evaluateConstantExpressionOrIdentifierAsLiteral(engine_args[0], args.local_context);

        String url = engine_args[0]->as<ASTLiteral &>().value.safeGet<String>();

        engine_args[1] = evaluateConstantExpressionOrIdentifierAsLiteral(engine_args[1], args.local_context);

        String format_name = engine_args[1]->as<ASTLiteral &>().value.safeGet<String>();

        return StorageHDFS::create(url, args.database_name, args.table_name, format_name, args.columns, args.context);
    });
}

}

#endif