Method checkForUpgrade

db/crud.go:3474–3485

Checks whether a document has a mobile xattr. Used when running in non-xattr mode to support no downtime upgrade.

(ctx context.Context, key string, unmarshalLevel DocumentUnmarshalLevel)

// Checks whether a document has a mobile xattr.  Used when running in non-xattr mode to support no downtime upgrade.
func (c *DatabaseCollection) checkForUpgrade(ctx context.Context, key string, unmarshalLevel DocumentUnmarshalLevel) (*Document, *sgbucket.BucketDocument) {
	// If we are using xattrs or Couchbase Server doesn't support them, an upgrade isn't going to be in progress
	if c.UseXattrs() || !c.dataStore.IsSupported(sgbucket.BucketStoreFeatureXattrs) {
		return nil, nil
	}

	doc, rawDocument, err := c.GetDocWithXattrs(ctx, key, unmarshalLevel)
	if err != nil || doc == nil || !doc.HasValidSyncData() {
		return nil, nil
	}
	return doc, rawDocument
}

// legacyRevToHybridLogicalVector will take a legacy revID and convert it to a HybridLogicalVector, used for when a
// document doesn't have hlv defined (it is a legacy pre upgraded doc).