A CDS plugin for automatic capturing, storing, and viewing of change records for modelled entities.
Important
With version 2.0, we completely refactored how changes are tracked. Previously, the logic relied on the application layer, which limited the types of trackable queries and came with major performance penalties in larger projects. With v2.0 the changes are now fully tracked on the database layer via database triggers. Furthermore, the table definition for changes was cleaned up with v2.0. This means any upgrade involves a schema change.
- Try it Locally
- Detailed Explanation
- Advanced Options
- Examples
- Contributing
- Code of Conduct
- Licensing
To enable change tracking, simply add this self-configuring plugin package to your project and add the @changelog annotation to your data model, as explained in the Detailed Explanation.
npm add @cap-js/change-trackingAlternatively, a full sample application is provided in the tests/bookshop folder:
git clone https://github.com/cap-js/change-tracking
cd change-tracking
npm i
cd tests/bookshop
cds watchWarning
Please note that if your project is multi-tenant, then the CDS version must be higher than 8.6 and the mtx version higher than 2.5 for change-tracking to work.
Warning
When using multi-tenancy with MTX, the generated database triggers, facets and associations have to be created by the model provider of the MTX component. Therefore, the plugin also must be added to the package.json of the MTX sidecar.
Warning
Please be aware that sensitive or personal data (annotated with @PersonalData) is not change tracked, since viewing the log allows users to circumvent audit-logging.
All you need to do, is to identify what should be change-tracked by annotating respective entities and elements in your model with the @changelog annotation. Following the best practice of separation of concerns, we do so in a separate file db/change-tracking.cds:
using { sap.capire.Incidents, sap.capire.Conversations } from './schema.cds';
annotate Incidents {
customer @changelog: [customer.name];
title @changelog;
status @changelog;
}
annotate Conversations with @changelog: [author, timestamp] {
message @changelog @Common.Label: 'Message';
}The minimal annotation we require for change tracking is @changelog on elements, as for the elements title and status in the sample snippet above.
Additional identifiers or labels can be added to obtain more human-readable change records as described below.
With the steps above, we have successfully set up change tracking for our reference application. Let's see that in action.
- Start the server:
cds watch- Make a change on your change-tracked elements. This change will automatically be persisted in the database table (
sap.changelog.Changes) and made available in a pre-defined view, namely the Change History view for your convenience.
If you have a Fiori Element application, the CDS plugin automatically provides and generates a view sap.changelog.ChangeView, the facet of which is automatically added to the Fiori Object Page of your change-tracked entities/elements. In the UI, this corresponds to the Change History table which serves to help you to view and search the stored change records of your modeled entities.
By default the implementation looks up Object Type names or Field names from respective @title or @Common.Label annotations and uses the technical name as a fall back.
For example, without the @title annotation, changes to conversation entries would show up with the technical entity name:
With an annotation, and possible i18n translations like so:
annotate Incidents.conversations with @title: '{i18n>CONVERSATION}';We get a human-readable display for Object Type:
The changelog annotations for Object ID are defined at entity level.
Having a @changelog annotation without any additional identifiers, changes to conversation entries show up as simple entity IDs:
However, this is not advisable and the readability can be increased with an explicit object ID as follows:
annotate Incidents.conversation with @changelog: [author, timestamp];
The annotation accepts a list of paths, meaning the following examples are all possible as well:
type CustomType : String;
extend Customers with elements {
note: CustomType
}
annotate Incidents with @changelog: [
title, customer.note, urgency.name
];annotate Incidents with @changelog: [
customer.address.city, customer.address.streetAddress, status.criticality
] {
title @changelog;
}The changelog annotations for New Value and Old Value are defined at element level.
They are already human-readable by default, unless the @changelog definition cannot be uniquely mapped such as types enum or Association.
For example, having a @changelog annotation on Incident's customer field without any additional identifiers, changes would show up as UUIDs:
customer @changelog;
Hence, here it is essential to add a unique identifier to obtain human-readable value columns:
customer @changelog: [customer.name];
When a child entity is modified, a composition changelog entry is created on the parent entity with valueDataType = 'cds.Composition'. The Object ID on this entry identifies what was affected. How this Object ID is resolved depends on whether the composition is a composition of one or a composition of many.
For composition of one, the Object ID is derived from the child entity's @changelog annotation. If the child entity has no @changelog, it falls back to the parent entity's @changelog. Any @changelog annotation on the composition field itself is not considered for the Object ID.
@changelog: [name]
entity BookStores {
key ID : UUID;
name : String;
registry : Composition of one BookStoreRegistry @changelog: ('Not considered');
}
@changelog: [code]
entity BookStoreRegistry {
key ID : UUID;
code : String;
validOn : Date @changelog;
}When validOn is changed on BookStoreRegistry, the composition entry on BookStores will have objectID = 'TEST-REG' (from the child's @changelog: [code]), not the parent's name.
For composition of many, the Object ID is not derived from the child entity, since different children can have different identifiers. Instead, it falls back to the parent entity's @changelog annotation.
@changelog: [name]
entity BookStores {
key ID : UUID;
name : String;
books : Composition of many Books on books.bookStore = $self @changelog;
}
@changelog: [title]
entity Books {
key ID : UUID;
bookStore : Association to BookStores;
title : String @changelog;
}When a Books entry is modified, the composition entry on BookStores will have objectID = 'Shakespeare and Company' (from the parent's @changelog: [name]).
You can customize the Object ID on the composition field using @changelog with a path or an expression. The annotation must only reference elements from the parent entity, not from the child entity.
Path-based:
annotate BookStores with @changelog: [name] {
books @changelog: [name]; // uses parent's 'name' as Object ID
}Expression-based:
annotate BookStores with @changelog: [name] {
books @changelog: ('Books from ' || name); // evaluates to e.g. 'Books from Shakespeare and Company'
}Note
When multiple children are created or deleted in a single transaction, only one composition entry is created per parent.
Results in the following change logs:
In addition to plain paths, the @changelog annotation supports CDS expressions for computing human-readable labels. Expressions must be wrapped in parentheses () to distinguish them from paths:
annotate Incidents {
status @changelog: (status.code || ': ' || status.descr);
price @changelog: (price < 100 ? 'Budget' : 'Premium');
}When status changes from N (New) to R (Resolved), the label would show "N: New" and "R: Resolved" instead of raw key values. For price, a ternary expression classifies the value into a human-readable category.
If a human-readable value is annotated for the changelog, it will be localized.
extend Incidents with elements {
status: Association to one Status @changelog: [status.descr];
}
entity Status {
key code: String(1);
descr: localized String(20);
}By default the value label stored for the change is localized in the language of the user who caused the change. Meaning if a German speaking user changes the status, the human-readable value would be by default in German.
In cases, like above, where the human-readable value only consists of one field, targets a localized property and goes along the (un-)managed association, a dynamic human-readable value is used, meaning if an English-speaking user looks at the changes, the value label will be shown in English, for a French-speaking user in French and so on.
Change tracking is implemented with Database triggers and supports HANA Cloud, SQLite, Postgres and H2.
Leveraging database triggers means any change will be tracked no matter how it is represented in the service. Thus tracking changes made via unions, or via views with joins will still work.
The plugin supports tracking datetime field changes when the field has a time zone annotated.
extend Incidents with elements {
closedAt : DateTime @changelog @Common.Timezone : 'Europe/Berlin';
openedAt : DateTime @changelog @Common.Timezone : openedTimeZone;
openedTimeZone : String @Common.IsTimezone;
}In both cases the plugin will show the annotated time zone for change values in changes for the two fields. In the second case the time zone is dynamically fetched and modifications to the time zone field will also reflect in the change records for that field.
The Change History view can be easily adapted and configured to your own needs by simply changing or extending it. For example, let's assume we only want to show the first 5 columns in equal spacing, we would extend db/change-tracking.cds as follows:
using from '@cap-js/change-tracking';
annotate sap.changelog.ChangeView with @(
UI.LineItem : [
{ Value: modificationLabel },
{ Value: createdAt },
{ Value: createdBy },
{ Value: entityLabel },
{ Value: objectID }
]
);In the UI, the Change History table now contains only the five columns with the desired properties:
For more information and examples on adding Fiori Annotations, see Adding SAP Fiori Annotations.
To disable the lazy loading feature of the Change History table, you can add the following annotation to your db/change-tracking.cds:
using from '@cap-js/change-tracking';
annotate sap.changelog.aspect @(UI.Facets: [{
$Type : 'UI.ReferenceFacet',
ID : 'ChangeHistoryFacet',
Label : '{i18n>ChangeHistory}',
Target: 'changes/@UI.PresentationVariant',
@UI.PartOfPreview
}]);The system now uses the SAP Fiori elements default setting @UI.PartOfPreview: true, such that the table will always be shown when navigating to that respective Object page.
If you do not want the auto-provided UI facet for viewing changes, you can provide your own facet for the changes association in the @UI.Facets annotation and the plugin won't override it.
Furthermore if you annotate the association as not readable, the facet is also not added. You can achive this, like
@Capabilities.NavigationRestrictions.RestrictedProperties : [
{
NavigationProperty : changes,
ReadRestrictions : {
Readable : false,
},
},
]
entity SalesOrders {
key ID : Int16;
title : String @changelog;
}For some scenarios, e.g. when doing UNION and the @changelog annotation is still propagated, the automatic addition of the association to changes does not make sense. You can use @changelog.disable_assocfor this to be disabled on entity level.
Important
This will also suppress the addition of the UI facet, since the change-view is no longer available as the target entity.
If you do not want to track some types of changes, you can disable them using disableCreateTracking, disableUpdateTracking
and disableDeleteTracking configs in your project settings:
{
"cds": {
"requires": {
"change-tracking": {
"disableCreateTracking": true,
"disableUpdateTracking": false,
"disableDeleteTracking": true
}
}
}
}By default, deleting a record will also automatically delete all associated change logs. This helps reduce the impact on the size of the database.
You can turn this behavior off globally by adding the following switch to the package.json of your project
"cds": {
"requires": {
"change-tracking": {
"preserveDeletes": true
}
}
}Important
Preserving the change logs of deleted data can have a significant impact on the size of the change logging table, since now such data also survives automated data retention runs. You must implement an own data retention strategy for the change logging table in order to manage the size and performance of your database.
By default, the depth of the changes hierarchy for any entity is 3. This means, its changes as well as the changes of its compositions and the compositions of its compositions are shown on the UI.
"cds": {
"requires": {
"change-tracking": {
"maxDisplayHierarchyDepth": 3
}
}
}Important
The depth of the hierarchy has a performance impact, so be careful with increasing it!
Localized properties, like descr in the example, are respected and the localized value during change log creation is used for the label.
entity Incidents : cuid, managed {
// … more fields
status : Association to Status default 'N' @changelog : [status.descr];
}
entity Status {
key code : String:
descr : localized String;
}Please be aware this means the localized value is then stored and shown in the change log, e.g. if a user speaking another language accesses the change log later, they will still see the value in the language used by the user who caused the change log.
This section describes modelling cases for further reference, from simple to complex, including the following:
- Tracing Changes
- Use Case 1: Trace the changes of child nodes from the current entity and display the meaningful data from child nodes (composition relation)
- Use Case 2: Trace the changes of associated entities from the current entity and display the meaningful data from associated entities (association relation)
- Use Case 3: Trace the changes of chained associated entities from the current entity and display the meaningful data from associated entities (association relation)
- Don'ts
Use cases for tracing changes
Use Case 1: Trace the changes of child nodes from the current entity and display the meaningful data from child nodes (composition relation)
Modelling in db/schema.cds
entity Incidents : managed, cuid {
...
title : String @title: 'Title';
conversation : Composition of many Conversation;
...
}
aspect Conversation: managed, cuid {
...
message : String;
}Add the following @changelog annotations in db/change-tracking.cds
annotate Incidents with @changelog: [title] {
conversation @changelog;
}
annotate Conversation with @changelog: [message] {
message @changelog;
}When a Conversation entry is modified, the composition changelog entry on Incidents will automatically use the child's Object ID derived from Conversation @changelog: [message]. This way, the change history on the parent shows which conversation was affected.
Use Case 2: Trace the changes of associated entities from the current entity and display the meaningful data from associated entities (association relation)
Modelling in db/schema.cds
entity Incidents : cuid, managed {
...
customer : Association to Customers;
title : String @title: 'Title';
...
}
entity Customers : cuid, managed {
...
email : EMailAddress;
...
}Add the following @changelog annotations in db/change-tracking.cds
annotate Incidents with @changelog: [title] {
customer @changelog: [customer.email];
}Use Case 3: Trace the changes of chained associated entities from the current entity and display the meaningful data from associated entities (association relation)
Modelling in db/schema.cds
entity Incidents : cuid, managed {
...
title : String @title: 'Title';
customer : Association to Customers;
...
}
entity Customers : cuid, managed {
...
address : Composition of one Addresses;
...
}Add the following @changelog annotations in db/change-tracking.cds
annotate Incidents with @changelog: [title] {
customer @changelog: [customer.address.city, customer.address.streetAddress];
}Change-tracking supports analyzing chained associated entities from the current entity in case the entity in consumer applications is a pure relation table. However, the usage of chained associated entities is not recommended due to performance cost.
entity Customers : cuid, managed {
...
incidents : Association to many Incidents on incidents.customer = $self;
}The reason is that: the relationship: Association to many is only for modelling purpose and there is no concrete field in database table. In the above sample, there is no column for incidents in the table Customers, but there is a navigation property of incidents in Customers OData entity metadata.
entity AggregatedBusinessTransactionData @(cds.autoexpose) : cuid {
FootprintInventory: Association to one FootprintInventories
on FootprintInventory.month = month
and FootprintInventory.year = year
and FootprintInventory.FootprintInventoryScope.ID = FootprintInventoryScope.ID;
...
}The reason is that: When deploying to relational databases, Associations are mapped to foreign keys. Yet, when mapped to non-relational databases they're just references. More details could be found in Prefer Managed Associations. In the above sample, there is no column for FootprintInventory in the table AggregatedBusinessTransactionData, but there is a navigation property FootprintInventory of in OData entity metadata.
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