Method getRevision

db/crud.go:691–726

Gets a revision of a document. If it's obsolete it will be loaded from the database if possible. inline "_attachments" properties in the body will be extracted and returned separately if present (pre-2.5 metadata, or backup revisions)

(ctx context.Context, doc *Document, revid string)

// Gets a revision of a document. If it's obsolete it will be loaded from the database if possible.
// inline "_attachments" properties in the body will be extracted and returned separately if present (pre-2.5 metadata, or backup revisions)
func (c *DatabaseCollection) getRevision(ctx context.Context, doc *Document, revid string) (bodyBytes []byte, attachments AttachmentsMeta, channels base.Set, err error) {
	bodyBytes = doc.getRevisionBodyJSON(ctx, revid, c.RevisionBodyLoader)

	// No inline body, so look for separate doc:
	if bodyBytes == nil {
		if !doc.History.contains(revid) {
			return nil, nil, nil, ErrMissing
		}

		bodyBytes, channels, _, err = c.getOldRevisionJSON(ctx, doc.ID, revid)
		if err != nil || bodyBytes == nil {
			return nil, nil, nil, err
		}
	}

	if channels == nil {
		// ignore ok value - we don't care if this is a leaf or not, if we have the data to get channels we'll use it
		channels, _ = doc.channelsForRevTreeID(revid)
	}

	// optimistically grab the doc body and to store as a pre-unmarshalled version, as well as anticipating no inline attachments.
	if doc.GetRevTreeID() == revid {
		attachments = doc.Attachments()
	}

	// handle backup revision inline attachments, or pre-2.5 meta
	if inlineAtts, cleanBodyBytes, _, err := extractInlineAttachments(bodyBytes); err != nil {
		return nil, nil, nil, err
	} else if len(inlineAtts) > 0 {
		// we found some inline attachments, so merge them with attachments, and update the bodies
		attachments = mergeAttachments(inlineAtts, attachments)
		bodyBytes = cleanBodyBytes
	}

	return bodyBytes, attachments, channels, nil
}

// mergeAttachments copies the attachmentsB map, and merges attachmentsA into it. If both maps are nil, return nil.
// Conflicting attachment names fall back to a revpos comparison - highest wins. If equivalent, attachment from attachmentsB wins.