# MERGE (upsert) `rows` into `table` by the key columns `on` (e.g. `["occurred_at"]` or

`POST /datanotes/operations/merge_rows/` (operation `merge_rows`)

MERGE (upsert) `rows` into `table` by the key columns `on` (e.g. `["occurred_at"]` or
`["id"]`): a row matching an existing one updates it (`when_matched`: "update" default or
"ignore"), the others are inserted (`when_not_matched`: "insert" default or "ignore").
Date-times are compared after completion with the database time zone. A source key matching
several rows, or repeated, is a conflict. One journaled, undoable operation.

## Parameters

| Name | In | Type | Required | Description |
| --- | --- | --- | --- | --- |
| `X-Datanotes-Actor` | header | `string` | no | JSON: on whose behalf the write is made, recorded in the journal (`harness`, `model`, `session`). |

## Request body

`application/json`, required

| Property | Type | Required | Default | Description |
| --- | --- | --- | --- | --- |
| `table` | `string` | yes |  |  |
| `on` | `string[]` | yes |  |  |
| `rows` | `object[]` | yes |  |  |
| `when_matched` | `"update" \| "ignore" \| null` | no | `null` |  |
| `when_not_matched` | `"insert" \| "ignore" \| null` | no | `null` |  |
| `dry_run` | `boolean` | no | `false` |  |

## Responses

| Status | Description | Body |
| --- | --- | --- |
| 200 | Done. | `OpResult` (application/json) |
| 400 | Bad input: the body is not a JSON object, or an argument is unknown, missing or of the wrong type. | `Error` (application/json) |
| 401 | Missing or wrong bearer token. | `Error` (application/json) |
| 403 | A named token beyond its permissions (the engine's administration, tables outside its `write` patterns, schema changes without `ddl`). | `Error` (application/json) |
| 404 | Unknown table, view, migration, note or folder. | `Error` (application/json) |
| 409 | Ambiguous table name: it matches several tables (`paths` or `tables` lists them). | `AmbiguousName` (application/json) |
| 422 | Refused (validation failures, conflicts, an unmet `expect`): nothing written. Same body as 200, with `ok: false` and the reasons. | `OpResult` (application/json) |
| 500 | Unexpected error (`{error}`), or a write that failed partway and could not be rolled back: `rolled_back: false`, `failed` lists the files left (undo_migration on `migration_id` retries the rollback). | `OpResult \| Error` (application/json) |
| 503 | A write that failed partway (a file another program holds) and was rolled back: `rolled_back: true`, nothing written. Send it again later. Same body as 200, with `ok: false` and `failed`. | `OpResult` (application/json) |

The schemas named here are in [openapi.json](https://datanotes.dev/openapi.json) (`components.schemas`).