[source-mongo] Connector stores the `_id` of deleted rows as a raw JSON object

[almihor]

Connector Name

source-mongo

Connector Version

1.5.17

What step the error happened?

During the sync

Relevant information

During CDC incremental syncs, the connector stores the _id of deleted rows as a raw JSON object:

{
  "_id": "{\"$binary\": {\"base64\": \"k7N/P5EMF4SZmAGW2Hx4sg==\",\"subType\": \"03\"}}",
  "_ab_cdc_updated_at": "2025-05-22T17:19:42Z",
  "_ab_cdc_cursor": 174793503000000271,
  "_ab_cdc_deleted_at": "2025-05-22T17:19:42Z"
}

For rows that aren’t deleted, the _id field contains the expected Base64 string:

{
  "_id": "9gi3oVVEm42XxgGW9/YrGg==",
  "Liked": true,
  "Text": null,
  "UpdatedAt": {
    "DateTime": "2025-05-22T12:27:07.418Z",
    "Ticks": 638835136274184098,
    "Offset": 0
  },
  "_ab_cdc_updated_at": "2025-05-22T12:27:07Z",
  "_ab_cdc_cursor": 174791722900000287,
  "_ab_cdc_deleted_at": null
}

These examples come from destination-mssql v1.0.2, because I encountered issues with newest version of connector due to this behavior.

Relevant log output

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