> For the complete documentation index, see [llms.txt](https://docs.appfarm.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.appfarm.io/reference/platform-concepts/filters.md). # Filters Filters are used with data sources to create a subset of data. You can set a filter directly on a data source when it's created, or apply a filter to a data source in the UI or actions. Filters are continuously evaluated, so objects can be dynamically added and removed while an app is in use. ## Usage Filters are [configured in the same way as conditions](/reference/platform-concepts/conditions.md#condition-editor), and rely on the same [operators](/reference/platform-concepts/operators.md), but always return a data source with 0 or more objects. Filters can be applied in the following cases: ### App data sources When you add an object class as a data source to an app, you should usually add a filter. The filter determines which data should be read from the database into the data source. See [server-side vs. client-side filters](#server-side-vs.-client-side-filters) for more information on why filters are important on data sources. A data source filter has no object in context. When the filter compares with a value from a data source with cardinality many, the value is read from that data source's single selected object (**Single Selected**). In UI, action and function filters the option is **Context / Single Selected**: the object in context, or the single selected object when there is none. ### Iterating UI components Filters can be applied to iterating [containers](/library/ui-components/container.md), Select, [Multi Select](/library/ui-components/multi-select.md), [Radio buttons](/library/ui-components/radio-buttons.md), [Table](/library/ui-components/table.md), Data Grid, [List](/library/ui-components/list.md), Chip group, Avatar group, Map layers, and [Chart](/library/ui-components.md#basic-charts) components, including Gantt and gauge charts. In this case the filter acts as an additional filter to the one applied directly to the data source. This is referred to as *UI filtering* and applies only in the context of that single UI component. You can also add conditional filters, which are enabled when a specific [condition](/reference/platform-concepts/conditions.md) is true. These are often used to provide users with filters they can apply dynamically while they use the app. ### Action nodes In the [For each action node](/library/action-nodes/foreach.md), which loops through the objects in a data source, you can apply a filter to the data source. Only the objects that match the filter will be iterated. In the [Read objects](/library/action-nodes/read-objects.md), [Update object](/library/action-nodes/update-object.md), and [Delete objects](/library/action-nodes/delete-objects.md) action nodes, you can specify that the **Selection** is a `Filtered selection` and add a filter. The action will then only affect the objects that match the filter. ### Functions In the function editor, when you add a multi-cardinality data source as a function parameter, you can specify that the **Selection** is a `Filtered selection` and add a filter. The parameter will only contain the objects that match the filter. ### Conditions When you create an expression in the [condition editor](/reference/platform-concepts/conditions.md#condition-editor) that uses the *Exists in* or *Not exist in* operators, you can define a filtered selection from a data source as the right operand. ## Server-side vs. client-side filters In general, filters can be applied both server-side and client-side. A filter applied using the **Filter** property on database connected data sources in apps is a server-side filter. The filter is applied on the server, and only the objects which meet the criteria of the filter are sent to the app. Server-side filters reduce how much data is sent to the app, which helps performance. They are not a security boundary: filter inputs come from the app, and the same user can query the data in other ways. Use object class permissions to decide who may see what (see [Designing secure permissions](/reference/security/permissions/designing-secure-permissions.md)). All other filters, such as those applied in the UI or in actions, are client-side filters. This includes filters added using the [**Client Filters**](/reference/apps/data/data-sources.md#client-filters) property on database connected data sources. For example, say you have a database connected data source *Orders*, that contains all orders from the last 3 months. You then apply a filter with the expression `Order.Responsible EQUALS Current User` in a table in a view called *My Orders*. This filter will be applied at the moment the view has evaluated that the table should be displayed in your app, and is run in the browser. --- # Agent Instructions This documentation is published with GitBook. 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