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62 lines
2.3 KiB
Markdown
62 lines
2.3 KiB
Markdown
# What is a metadata delta?
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Rest.li supports [partial update](https://linkedin.github.io/rest.li/user_guide/restli_server#partial_update) natively without needing explicitly defined models.
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However, the granularity of update is always limited to each field in a PDL model.
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There are cases where the update need to happen at an even finer grain, e.g. adding or removing items from an array.
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To this end, we’re proposing the following entity-specific metadata delta model that allows atomic partial updates at any desired granularity.
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Note that:
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1. Just like metadata [aspects](aspect.md), we’re not imposing any limit on the partial update model, as long as it’s a valid PDL record.
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This is because the rest.li endpoint will have the logic that performs the corresponding partial update based on the information in the model.
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That said, it’s common to have fields that denote the list of items to be added or removed (e.g. `membersToAdd` & `membersToRemove` from below)
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2. Similar to metadata [snapshots](snapshot.md), entity that supports metadata delta will add an entity-specific metadata delta
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(e.g. `GroupDelta` from below) that unions all supported partial update models.
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3. The entity-specific metadata delta is then added to the global `Delta` typeref, which is added as part of [Metadata Change Event](mxe.md#metadata-change-event-mce) and used during [Metadata Ingestion](../architecture/metadata-ingestion.md).
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```
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namespace com.linkedin.group
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import com.linkedin.common.CorpuserUrn
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/**
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* A metadata delta for a specific group entity
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*/
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record MembershipPartialUpdate {
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/** List of members to be added to the group */
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membersToAdd: array[CorpuserUrn]
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/** List of members to be removed from the group */
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membersToRemove: array[CorpuserUrn]
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}
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```
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```
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namespace com.linkedin.metadata.delta
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import com.linkedin.common.CorpGroupUrn
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import com.linkedin.group.MembershipPartialUpdate
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/**
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* A metadata delta for a specific group entity
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*/
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record GroupDelta {
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/** URN for the entity the metadata delta is associated with */
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urn: CorpGroupUrn
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/** The specific type of metadata delta to apply */
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delta: union[MembershipPartialUpdate]
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}
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```
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```
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namespace com.linkedin.metadata.delta
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/**
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* A union of all supported metadata delta types.
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*/
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typeref Delta = union[GroupDelta]
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```
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