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| 在 OneLake 上的 Direct Lake |Utilizes the Delta Parquet storage format to quickly swap the data into semantic model memory when needed.| 当你的数据已以表或物化视图的形式存在于 Fabric Warehouse 或 Lakehouse 中时。 |
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| 在 SQL 上的 Direct Lake | Direct Lake 的旧版本,使用 Fabric Warehouse 或 Lakehouse 的 SQL analytics endpoint。 | 不建议用于新开发(改用在 OneLake 上的 Direct Lake)。 |
[在 OneLake 上的 Direct Lake](https://learn.microsoft.com/en-us/fabric/fundamentals/direct-lake-overview#key-concepts-and-terminology) 于 2025 年三月推出,作为在 SQL 上的 Direct Lake 的替代方案。 使用在 OneLake 上的 Direct Lake 时,不依赖 SQL 端点,也不会回退到 DirectQuery 模式。 这也意味着,适用于 DirectQuery 模型的[常见限制](https://learn.microsoft.com/en-us/power-bi/connect-data/desktop-directquery-about#modeling-limitations)不适用于在 OneLake 上的 Direct Lake 模型。
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不过,与在 SQL 上的 Direct Lake 一样,仍然有一些[确实适用的限制](https://learn.microsoft.com/en-us/fabric/fundamentals/direct-lake-overview#considerations-and-limitations)。 下面列出最重要的限制。 完整限制列表请参阅该链接:
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> [!NOTE]
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> Direct Lake on OneLake is currently in public preview. You must enable the tenant setting **User can create Direct Lake on OneLake semantic models (preview)** in the Fabric admin portal before you can create semantic models with this table storage mode.
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不过,与在 SQL 上的 Direct Lake 一样,仍然有一些[确实适用的限制](https://learn.microsoft.com/en-us/fabric/fundamentals/direct-lake-overview#considerations-and-limitations)。 Key limitations include:
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- Calculated columns are not supported in either Direct Lake mode.
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- Calculated tables cannot reference columns or tables in Direct Lake storage mode. Calculation groups, what-if parameters and field parameters are supported because they create implicit calculated tables that do not reference Direct Lake columns.
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- Non-materialized SQL views are not supported as data sources for Direct Lake on OneLake tables. Use materialized views or ensure the source Delta table contains the columns you need.
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- Shortcuts in a lakehouse are not supported as data sources during the public preview of Direct Lake on OneLake.
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- Direct Lake 表上的计算列不能引用源自 OneLake 的列。
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- Direct Lake 模型中的计算表格不能引用源自 OneLake 的 Direct Lake 表中的列。
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For a full and up-to-date list of limitations, see the [Microsoft documentation on Direct Lake considerations and limitations](https://learn.microsoft.com/en-us/fabric/fundamentals/direct-lake-overview#considerations-and-limitations).
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针对上述限制的一种可行变通方案,是通过将 Direct Lake 表与导入表组合,创建一个**复合模型**。 在 OneLake 上的 Direct Lake 允许这样做,但在 SQL 上的 Direct Lake 不允许。 在这种情况下,通常会对较小的维度表使用导入模式,因为可能需要添加自定义分组,而计算列非常适合用于此,同时将较大的事实表保持为 Direct Lake 模式。
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### Composite models
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或者,确保源中包含所需的列。 如果通过视图添加列,请注意该视图必须在 Fabric Warehouse 或 Lakehouse 中物化,因为 OneLake 上的 Direct Lake 不支持非物化视图。
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One workaround for the calculated column limitation is to create a **composite model** by combining Direct Lake tables with Import tables. This is supported with Direct Lake on OneLake, but not with Direct Lake on SQL. In a composite model, you typically keep larger fact tables in Direct Lake mode while using Import mode for smaller dimension tables where you need calculated columns or custom groupings.
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Direct Lake on OneLake also supports combining with DirectQuery tables through XMLA-based tools such as Tabular Editor. Import tables can be added through Power BI web modeling, Power BI Desktop (live editing) or through XMLA tools.
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> [!NOTE]
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> Direct Lake on SQL does not support composite models. You cannot combine Direct Lake on SQL tables with Import, DirectQuery or Dual storage mode tables in the same semantic model. However, you can use Power BI Desktop to create a composite model _on top of_ a Direct Lake on SQL semantic model and extend it with new tables. See [Build a composite model on a semantic model](https://learn.microsoft.com/en-us/power-bi/transform-model/desktop-composite-models#building-a-composite-model-on-a-semantic-model-or-model) for more information.
> 一旦元数据已部署到 Analysis Services / Power BI,你就无法更改模型的排序规则。 因此,如果你打算用 SQL 上的 Direct Lake 连接到区分大小写的 Fabric Warehouse,你必须在部署之前先在模型元数据上设置排序规则:
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> 一旦元数据已部署到 Analysis Services / Power BI,你就无法更改模型的排序规则。 As such, if you plan to use Direct Lake on SQL with a case-sensitive Fabric Warehouse, you must set the collation on the model metadata before it is deployed:
1.**创建共享表达式**:Direct Lake 表使用“Entity”分区,该分区必须引用模型中的共享表达式。 如果你还没有该共享表达式,请先创建它。 将其命名为 `DatabaseQuery`:
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1.**Create Shared Expression**: Direct Lake tables use "Entity" partitions, which must reference a Shared Expression in the model. Start by creating this shared expression, if you do not have it already. 将其命名为 `DatabaseQuery`:
2.**配置共享表达式**:将你在步骤 1 中创建的表达式的**Kind**属性设为“M”,并将 **Expression**属性设置为以下 M 查询,同时将 URL 中的 ID 替换为你的 Fabric Workspace 和 Lakehouse/Warehouse 对应的 ID:
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2.**Configure Shared Expression**: Set the**Kind**property of the expression you created in step 1 to "M", and set the **Expression**property to the following M query, replacing the IDs in the URL for your Fabric workspace and Lakehouse/Warehouse:
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