Method getOldRevisionJSON

db/revision.go:246–287

getOldRevisionJSON looks up the raw JSON data of a revision that's been archived to a separate doc. If the revision isn't found (e.g. has been deleted by compaction) returns 404 error.

(ctx context.Context, docid string, revOrCV string)

// getOldRevisionJSON looks up the raw JSON data of a revision that's been archived to a separate doc.
// If the revision isn't found (e.g. has been deleted by compaction) returns 404 error.
func (c *DatabaseCollection) getOldRevisionJSON(ctx context.Context, docid string, revOrCV string) ([]byte, base.Set, bool, error) {
	data, _, err := c.dataStore.GetRaw(oldRevisionKey(docid, revOrCV))
	if base.IsDocNotFoundError(err) {
		base.DebugfCtx(ctx, base.KeyCRUD, "No old revision %q / %q", base.UD(docid), revOrCV)
		return nil, nil, false, ErrMissing
	} else if err != nil {
		return nil, nil, false, err
	}
	kind, revData := stripNonJSONPrefix(data)
	switch kind {
	case nonJSONPrefixKindRevBody:
		base.DebugfCtx(ctx, base.KeyCRUD, "Got old revision %q / %q --> %d bytes", base.UD(docid), revOrCV, len(revData))
		return revData, nil, false, nil
	case nonJSONPrefixKindRevPtr:
		// pointer to a CV-keyed backup revision - do another fetch by CV for the body
		base.DebugfCtx(ctx, base.KeyCRUD, "Found old revision pointer %q -> %q / %q", revOrCV, base.UD(docid), string(revData))
		return c.getOldRevisionJSON(ctx, docid, string(revData))
	case nonJSONPrefixKindRevWithMeta:
		jsonBody, meta, err := getOldRevisionJSONAndMeta(revData)
		if err != nil {
			return nil, nil, false, err
		}
		base.DebugfCtx(ctx, base.KeyCRUD, "Got old revision (with %d meta properties) %q / %q --> %d bytes", len(meta), base.UD(docid), revOrCV, len(jsonBody))
		var channelSet base.Set
		if ch, ok := meta[backupRevisionChannelsMetaKey]; ok && ch != nil {
			err = base.JSONUnmarshal(ch, &channelSet)
			if err != nil {
				return nil, nil, false, fmt.Errorf("error unmarshalling _channels xattr for old revision %q / %q: %v", base.UD(docid), revOrCV, err)
			}
		}
		var deletedDoc bool
		if deletedMeta, ok := meta[backupRevisionBodyDeletedMetaKey]; ok && deletedMeta != nil {
			err = base.JSONUnmarshal(deletedMeta, &deletedDoc)
			if err != nil {
				return nil, nil, false, fmt.Errorf("error unmarshalling _deleted xattr for old revision %q / %q: %v", base.UD(docid), revOrCV, err)
			}
		}
		return jsonBody, channelSet, deletedDoc, nil
	default:
		return nil, nil, false, fmt.Errorf("unexpected prefix %b for old revision doc %q / %q", kind, base.UD(docid).String(), revOrCV)
	}
}

func getOldRevisionJSONAndMeta(payload []byte) (jsonBody []byte, kvPairs map[string][]byte, err error) {
	body, meta, err := sgbucket.DecodeValueWithAllXattrs(payload)