从 ByteArrayOutputStream 而不是文件读取镶木地板数据

Question

我想转换这段代码：

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.parquet.column.page.PageReadStore;
import org.apache.parquet.example.data.simple.SimpleGroup;
import org.apache.parquet.example.data.simple.convert.GroupRecordConverter;
import org.apache.parquet.hadoop.ParquetFileReader;
import org.apache.parquet.hadoop.util.HadoopInputFile;
import org.apache.parquet.io.ColumnIOFactory;
import org.apache.parquet.io.MessageColumnIO;
import org.apache.parquet.io.RecordReader;
import org.apache.parquet.schema.MessageType;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;


public class ParquetReaderUtils {

    public static Parquet getParquetData(String filePath) throws IOException {
        List<SimpleGroup> simpleGroups = new ArrayList<>();
        ParquetFileReader reader = ParquetFileReader.open(HadoopInputFile.fromPath(new Path(filePath), new Configuration()));
        MessageType schema = reader.getFooter().getFileMetaData().getSchema();
        //List<Type> fields = schema.getFields();
        PageReadStore pages;
        while ((pages = reader.readNextRowGroup()) != null) {
            long rows = pages.getRowCount();
            MessageColumnIO columnIO = new ColumnIOFactory().getColumnIO(schema);
            RecordReader recordReader = columnIO.getRecordReader(pages, new GroupRecordConverter(schema));

            for (int i = 0; i < rows; i++) {
                SimpleGroup simpleGroup = (SimpleGroup) recordReader.read();
                simpleGroups.add(simpleGroup);
            }
        }
        reader.close();
        return new Parquet(simpleGroups, schema);
    }
}

（来自https://www.arm64.ca/post/reading-parquet-files-java/）

采用 ByteArrayOutputStream 参数而不是 filePath。

这可能吗？我在 org.apache.parquet.hadoop 中没有看到 ParquetStreamReader。

感谢任何帮助。我正在尝试为来自 kafka 的镶木地板编写一个测试应用程序，并且将许多消息中的每一条都写入文件相当慢。

Answer 1

所以如果没有更深入的测试，我会尝试使用这个类（尽管输出流的内容应该是 parquet 兼容的）。我放了一个streamId，以便更容易识别已处理的字节数组（如果出现问题，ParquetFileReader 会打印 instance.toString()）。

public class ParquetStream implements InputFile {
    private final String streamId;
    private final byte[] data;

    private static class SeekableByteArrayInputStream extends ByteArrayInputStream {
        public SeekableByteArrayInputStream(byte[] buf) {
            super(buf);
        }

        public void setPos(int pos) {
            this.pos = pos;
        }

        public int getPos() {
            return this.pos;
        }
    }

    public ParquetStream(String streamId, ByteArrayOutputStream stream) {
        this.streamId = streamId;
        this.data = stream.toByteArray();
    }

    @Override
    public long getLength() throws IOException {
        return this.data.length;
    }

    @Override
    public SeekableInputStream newStream() throws IOException {
        return new DelegatingSeekableInputStream(new SeekableByteArrayInputStream(this.data)) {
            @Override
            public void seek(long newPos) throws IOException {
                ((SeekableByteArrayInputStream) this.getStream()).setPos((int) newPos);
            }

            @Override
            public long getPos() throws IOException {
                return ((SeekableByteArrayInputStream) this.getStream()).getPos();
            }
        };
    }

    @Override
    public String toString() {
        return "ParquetStream[" + streamId + "]";
    }
}