# Sync mapping

Sync mappings tie Smartstore entities to records in external systems. Each record stores the internal entity identifier together with the external key and a context name that identifies the integration (for example `"ERP"` or `"PIM"`). Mappings are unique per `(EntityId, EntityName, ContextName)` and per `(SourceKey, EntityName, ContextName)` so sync operations stay idempotent.

## Schema

`SyncMapping` lives in `DbContext.SyncMappings` and is never cached. It contains the following fields:

* `EntityId` – identifier of the Smartstore entity.
* `EntityName` – entity type, usually `nameof(Product)`, `nameof(Category)` etc.
* `SourceKey` – primary key of the external record.
* `ContextName` – name of the remote system.
* `SourceHash` – optional checksum of the source payload to detect changes.
* `CustomInt`, `CustomString`, `CustomBool` – free-form metadata slots.
* `SyncedOnUtc` – timestamp of the last synchronization.

## Creating or updating a mapping

```csharp
var map = await _db.SyncMappings
    .SingleOrDefaultAsync(x => x.SourceKey == dto.Id
        && x.ContextName == "ERP"
        && x.EntityName == nameof(Product));

if (map == null)
{
    map = new SyncMapping {
        EntityId = product.Id,
        EntityName = nameof(Product),
        ContextName = "ERP",
        SourceKey = dto.Id
    };
    _db.SyncMappings.Add(map);
}

map.SourceHash = dto.Hash;
map.SyncedOnUtc = DateTime.UtcNow;
await _db.SaveChangesAsync();
```

## Resolving an entity by external key

```csharp
var map = await _db.SyncMappings
    .SingleOrDefaultAsync(x => x.SourceKey == dto.Id
        && x.ContextName == "ERP"
        && x.EntityName == nameof(Product));

if (map != null)
{
    var product = await _db.Products.FindAsync(map.EntityId);
}
```

Use `SyncMappingQueryExtensions.ApplyEntityFilter` to filter mappings by entity identifiers, entity name or context when cleaning up mappings or preparing batch jobs.

## Remote access

The Web API exposes `/odata/v1/SyncMappings` so remote applications can query or modify mappings using standard OData operations (`GET`, `POST`, `PATCH`, `PUT`, `DELETE`).


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://dev.smartstore.com/framework/advanced/sync-mapping.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.