Method GetDocSyncData

db/crud.go:161–217

This gets *just* the Sync Metadata (_sync field) rather than the entire doc, for efficiency reasons.

(ctx context.Context, docid string)

// This gets *just* the Sync Metadata (_sync field) rather than the entire doc, for efficiency reasons.
func (c *DatabaseCollection) GetDocSyncData(ctx context.Context, docid string) (SyncData, error) {

	emptySyncData := SyncData{}
	key := realDocID(docid)
	if key == "" {
		return emptySyncData, base.HTTPErrorf(400, "Invalid doc ID")
	}

	if c.UseXattrs() {
		// Retrieve doc and xattr from bucket, unmarshal only xattr.
		// Triggers on-demand import when document xattr doesn't match cas.
		rawDoc, xattrs, cas, getErr := c.dataStore.GetWithXattrs(ctx, key, c.syncGlobalSyncAndUserXattrKeys())
		if getErr != nil {
			return emptySyncData, getErr
		}

		// Unmarshal xattr only
		doc, unmarshalErr := c.unmarshalDocumentWithXattrs(ctx, docid, nil, xattrs, cas, DocUnmarshalSync)
		if unmarshalErr != nil {
			return emptySyncData, unmarshalErr
		}

		isSgWrite, crc32Match, _ := doc.IsSGWrite(ctx, rawDoc)
		if crc32Match {
			c.dbStats().Database().Crc32MatchCount.Add(1)
		}

		// If existing doc wasn't an SG Write, import the doc.
		if !isSgWrite {
			var importErr error

			doc, importErr = c.OnDemandImportForGet(ctx, docid, doc, rawDoc, xattrs, cas)
			if importErr != nil {
				return emptySyncData, importErr
			}
		}

		return doc.SyncData, nil

	} else {
		// Non-xattr.  Retrieve doc from bucket, unmarshal metadata only.
		rawDocBytes, _, err := c.dataStore.GetRaw(key)
		if err != nil {
			return emptySyncData, err
		}

		docRoot := documentRoot{
			SyncData: &SyncData{History: make(RevTree)},
		}
		if err := base.JSONUnmarshal(rawDocBytes, &docRoot); err != nil {
			return emptySyncData, err
		}

		return *docRoot.SyncData, nil
	}

}