Doc Snapshots Collection

docSnapshots holds copies of a doc that document-updater takes just before an edit that collapses comments or tracked changes. Only document-updater writes it, in services/document-updater/app/js/SnapshotManager.js. Web has a Mongoose model in services/web/app/src/models/DocSnapshot.mjs, but no code uses it.

Fields

Field	Type	Meaning	Source
_id	ObjectId	Snapshot id.	SnapshotManager.js:24
project_id	ObjectId	Project.	SnapshotManager.js:19,26, DocSnapshot.mjs:7
doc_id	ObjectId	The doc (docs._id).	SnapshotManager.js:20,27, DocSnapshot.mjs:8
version	Number	OT version of the doc before the edit.	SnapshotManager.js:28, services/document-updater/app/js/UpdateManager.js:132,264-271, DocSnapshot.mjs:9
lines	Array of String	Content of the doc before the edit.	SnapshotManager.js:29, DocSnapshot.mjs:10
pathname	String	Path of the doc in the project at that time.	SnapshotManager.js:30, DocSnapshot.mjs:11
ranges	Mixed	comments and changes before the edit, the same shape as docs.ranges (see docs). id, op.t and metadata.user_id are turned into ObjectIds and metadata.ts into Dates.	SnapshotManager.js:31,41-68, DocSnapshot.mjs:12
ts	Date	When the snapshot was taken. The TTL index deletes the snapshot 30 days later.	SnapshotManager.js:32, DocSnapshot.mjs:13

Who Writes It

Code	What it does
UpdateManager.js:248-271	After it applies an edit, document-updater records the doc as it was before the edit when the edit collapsed ranges: more ranges became empty, or more than one range was removed (services/document-updater/app/js/RangesManager.js:104-106).
SnapshotManager.js:17-36 recordSnapshot	Inserts the snapshot.

Who Reads It

No code reads it. The web model is defined but not used anywhere.

Indexes

Name	Keys	Options	Migration
ts_1	{ ts: 1 }	TTL, expireAfterSeconds: 2592000 (30 days)	tools/migrations/20190912145007_create_docSnapshots_indexes.mjs
project_id_1_ts_1	{ project_id: 1, ts: 1 }		tools/migrations/20200120163346_atlas_recommended_indexes.mjs

The project_id_1 index of 20190912145007_create_docSnapshots_indexes.mjs was dropped by 20231101191643_drop_unused_indexes.mjs.

Notes

• Only edits that go through UpdateManager.applyUpdate take snapshots. Edits handled by HistoryOTUpdateManager do not (UpdateManager.js:74-77).
• There is no index on doc_id. Find the snapshots of a doc by project_id and ts, then filter on doc_id.