diff.md

description
Fetch a list of forward or reverse commands (diffs) between commits for specified documents.

Diff

The Story So Far...

As we noticed in the previous section, one of the reporting edges had undergone more updates than expected. We will dig deeper into those extra updates in this section.

The offending edge in question had the id reporting/44799849.

{% hint style="success" %} We will use the GET variant of the DIFF endpoint in this guide, although the POST variant can also be used to achieve the same results. {% endhint %}

Diffs in Node-Brace Scope

Since we're only interested in fetching diffs for a single entity, we will use the node-brace scope here, which is the most efficient pre-filter to use when node ids are known in advance.

Since we're only interested in the updated events, we will omit the created and deleted events by using upper and lower time-bounds in the pre-filters:

1. The lower time bound will be the ctime of the first updated event in chronological order, since it is inclusive.
2. The upper time bound will be the ctime of the final updated event, since it is also inclusive.

We can get these values from the event log described in the last section. The request parameters would be as follows:

Param	Value
since	1588770714.352307
until	1588770928.5333633
path	/n/reporting/44799849

Response:

[
  {
    "node": "reporting/44799849",
    "commandsAreReversed": false,
    "events": [
      {
        "_id": "recallgraph_events/44801785",
        "_key": "44801785",
        "ctime": 1588770714.352307,
        "event": "updated",
        "last-snapshot": "recallgraph_snapshots/origin-44778934",
        "meta": {
          "rev": "_acmbKt---_"
        }
      },
      {
        "_id": "recallgraph_events/44802064",
        "_key": "44802064",
        "ctime": 1588770902.498967,
        "event": "updated",
        "last-snapshot": "recallgraph_snapshots/origin-44778934",
        "meta": {
          "rev": "_acmeCcG--_"
        }
      },
      {
        "_id": "recallgraph_events/44802110",
        "_key": "44802110",
        "ctime": 1588770928.5333633,
        "event": "updated",
        "last-snapshot": "recallgraph_snapshots/origin-44778934",
        "meta": {
          "rev": "_acmeb3S--_"
        }
      }
    ],
    "commands": [
      [
        {
          "op": "test",
          "path": "/_rev",
          "value": "_acmHVwO---"
        },
        {
          "op": "replace",
          "path": "/_rev",
          "value": "_acmbKt---_"
        },
        {
          "op": "test",
          "path": "/_to",
          "value": "employees/44794457"
        },
        {
          "op": "replace",
          "path": "/_to",
          "value": "employees/44794449"
        }
      ],
      [
        {
          "op": "test",
          "path": "/_rev",
          "value": "_acmbKt---_"
        },
        {
          "op": "replace",
          "path": "/_rev",
          "value": "_acmeCcG--_"
        }
      ],
      [
        {
          "op": "test",
          "path": "/_rev",
          "value": "_acmeCcG--_"
        },
        {
          "op": "replace",
          "path": "/_rev",
          "value": "_acmeb3S--_"
        }
      ]
    ]
  }
]

We can see the diffs, grouped by node (in this case, there's only one node), with each group containing a list of event in chronological order, followed by a list of commands corresponding to each event. These commands are listed in the JSON Patch (RFC6902) format, and therefore, are human-readable.

Conclusion

We see that the first diff is the one that effected a change in reporting structure, replacing the _to destination from Kyle to Eric. The remaining two commands did not record anything significant. They have been executed by the HRMS operator with no content changes, and so have no impact on the actual edge.