Question

我试图在这里做一个简单的MongoDB聚合。基本上我有这样的文件：

{
timestampInMs: 1444094140442,
records: [
{
value: "testvalue",
experiment: {
id: "56105b0af2763b25806d1365",
name: "integrationtest-kkkk",
created: "2015-10-03T22:47:38.479+0000",
updated: null
},
sensorId: "testsensor",
dataType: 1
},
{
value: "testvalue2",
experiment: {
id: "56105b0af2763b25806d1365",
name: "integrationtest-kkkk",
created: "2015-10-03T22:47:38.479+0000",
updated: null
},
sensorId: "testsensor2",
dataType: 1
},
{
value: "testvalue3",
experiment: {
id: "56105b0af2763b25806d1365",
name: "integrationtest-kkkk",
created: "2015-10-03T22:47:38.479+0000",
updated: null
},
sensorId: "testsensor3",
dataType: 1
},
{
value: "testvalue4",
experiment: {
id: "56105b0af2763b25806d1365",
name: "integrationtest-kkkk",
created: "2015-10-03T22:47:38.479+0000",
updated: null
},
sensorId: "testsensor4",
dataType: 1
}
],
created: "2015-10-06T01:15:40.501+0000",
updated: "2015-10-06T01:15:40.528+0000"
}

java模型看起来像这样

@Entity("sensordatadocs")
@Indexes ({
    @Index(fields = @Field("timestampInMs"), options = @IndexOptions(name = "timestamp_ms_index"))
})
public class DbSensorDataDocument {

    @Id
    // Should be milliseconds since Epoch
    private Long timestampInMs;

    @Embedded
    private List<DbSensorDataRecord> records;

    private Date created;

    private Date updated;
}

public class DbSensorDataRecord {

    private String value;

    @Reference
    private Experiment experiment;

    private String sensorId;

    private int dataType;
}

当我使用数据库查询时

db.sensordatadocs.aggregate([{$unwind: "$records"}])

它给了我4份文件，每份文件＆＃34;记录＆＃34;包含与原始数组中的项对应的单个项。但是，当我使用Morphia的API时，就像这样：

Iterator<DbSensorDataDocument> iter = datastore.createAggregation(DbSensorDataDocument.class)
        .unwind("records").aggregate(DbSensorDataDocument.class);

它将返回如下结果：

{
timestampInMs: 1444094140442,
sensorId: "testsensor",
value: "testvalue",
experimentId: "56105b0af2763b25806d1365",
dataType: 1
},
{
timestampInMs: 1444094140442,
sensorId: "testsensor",
value: "testvalue",
experimentId: "56105b0af2763b25806d1365",
dataType: 1
},
{
timestampInMs: 1444094140442,
sensorId: "testsensor",
value: "testvalue",
experimentId: "56105b0af2763b25806d1365",
dataType: 1
},
{
timestampInMs: 1444094140442,
sensorId: "testsensor",
value: "testvalue",
experimentId: "56105b0af2763b25806d1365",
dataType: 1
}

这就是我的迭代代码的样子：

while (iter.hasNext()) {
            DbSensorDataDocument doc = iter.next();
            final SensorDataRecord record = SensorDataUtils.flattenSensorDataDocument(doc);  
            result.add(record);
        }

请注意，项目数是正确的，但＆＃34;记录＆＃34;中的值是正确的。不正确，实际上它们只是原始数组中**第一个项的值。为什么会这样？请帮忙。谢谢！

Morphia版本1.0.1

Answer 1

该行为的原因是Morphia缓存问题。在您的情况下，Morphia将 DbSensorDataDocument 实体的所有结果视为同一行（因为相同的主键 timestampInMs ），并返回缓存版本。

要解决此问题，您必须从带有聚合投影的结果中排除字段 timestampInMs ：

Iterator<DbSensorDataDocument> iter = datastore.createAggregation(DbSensorDataDocument.class)
        .unwind("records").project(
 Projection.projection("timestampInMs").suppress(), 
 Projection.projection("XXXXXX").aggregate(DbSensorDataDocument.class);

XXXXX是您要包含的字段。

Morphia展开聚合返回的结果与Mongo数据库查询不同？

1 个答案: