---
title: "Backfill"
description: "one backfill of a source over a window, read in blocks with a ledger row (a Job) each: what it reads, by which way, at which code version, from a parse already made by the connector's own implementation where one is held, and how far it has got"
section: concepts
address: /concepts/backfill
contract: 0476e35e6e275db5
---

# Backfill

one backfill of a source over a window, read in blocks with a ledger row (a Job) each: what it reads, by which way, at which code version, from a parse already made by the connector's own implementation where one is held, and how far it has got

[figure: Backfill is a work at platform scope. The drawing shows its fields and the objects that they point at.]

| property | value |
|---|---|
| kind | work |
| scope | platform |
| key | the source, the way and the window |
| store | postgres |
| family | sources |



## Fields


| field | type | required | note |
|---|---|---|---|
| `source` | [Source](/concepts/source) | yes |  |
| `way` | [AccessMethod](/concepts/accessmethod) | yes |  |
| `window` | [Window](/concepts/window) | yes |  |
| `plane` | [Plane](/concepts/plane) | yes |  |
| `blocks` | `count` | yes | the blocks of the window, one a month for a monthly archive |
| `blocks_done` | `count` | yes |  |
| `code_version` | `text` | yes | the refine's code version: the parser's commit, or the release |
| `held_parse` | [SourceProcedure](/concepts/sourceprocedure) | no | Names the source procedure that records the folder that the connector's own parser wrote before the platform ran. The engine reads that folder in place (18 §2.25). Absent when the platform parses the block itself. |



## Routes that use it
No route takes or returns Backfill directly. The record holds it, and the objects that point at it reach it.