IndexRSerde.java 文件源码

@Override
public Object deserialize(Writable writable) throws SerDeException {

    // Different segments could contain different schemas.
    // Especially the column orders could be different.
    // Here we re-map the column names to the real column ids.

    SchemaWritable reader = (SchemaWritable) writable;
    if (this.projectCols != reader.columns) {
        // Don't have to do it every time, only when schema is changed.
        mapColIndex(reader.columns);
        projectCols = reader.columns;
    }

    if (!isMapNeeded) {
        serdeSize = columnNames.size();
        return reader;
    } else {
        Writable[] projectWritables = reader.get();
        Writable[] writables = new Writable[columnNames.size()];
        for (int i = 0; i < validColIndexes.length; i++) {
            int colIndex = validColIndexes[i];
            int mapColId = validColMapIds[i];
            writables[colIndex] = projectWritables[mapColId];
        }

        serdeSize = validColIndexes.length;
        return new ArrayWritable(Writable.class, writables);
    }
}