Cayenne User Documentation
Data Rows

DataObjects creation and registering with DataContext is an expensive operation. There are cases when only a few objects are really used, but the application still has to fetch a lot of objects. For instance when a user performs a search, result may contain thousands of records, but user will only check 2-3 of them. Cayenne allows programmers to explicitly disable objects creation for such cases. Results will be returned in the form of java.util.Map's. In Cayenne such maps are called `DataRows`.

Benefits of Data Rows:

- Fetch speed increase. Our tests show 2x to 5x performance increase.
- Using regular Cayenne query API.
- Using same DataMaps.
- Easy to convert to DataObjects.

Data rows don't have all the object-oriented features of DataObjects. In particular, data rows don't support relationships. It is easy to create a DataObject from a row though. See examples below.

Data rows example:

    import java.util.List;
    import java.util.Map;
    import org.apache.cayenne.access.DataContext;
    import org.apache.cayenne.query.SelectQuery;
    import org.apache.art.Artist;
    ...
    DataContext ctxt;

    // create a query returning data rows
    SelectQuery q = new SelectQuery(Artist.class);
    q.setFetchingDataRows(true);

    List artistRows = ctxt.performQuery(q);

    // since query was configured to return data rows,
    // result list elements are java.util.Map's
    Map row = (Map)artistRows.get(0);

    // convert row to an artist
    Artist artist = (Artist)ctxt.objectFromDataRow("Artist", row);
    ...

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