Function validateMutation

edgraph/server.go:719–765

validateMutation ensures that the value in the edge is not too big. The challange here is that the keys in badger have a limitation on their size (< 2<<16). We need to ensure that no key, either primary or secondary index key is bigger than that. See here for more details: https://github.com/dgraph-

(ctx context.Context, edges []*pb.DirectedEdge)

// We need to ensure that no key, either primary or secondary index key is bigger than that.
// See here for more details: https://github.com/dgraph-io/projects/issues/73
func validateMutation(ctx context.Context, edges []*pb.DirectedEdge) error {
	errValueTooBigForIndex := errors.New("value in the mutation is too large for the index")

	// key = meta data + predicate + actual key, this all needs to fit into 64 KB
	// we are keeping 536 bytes aside for meta information we put into the key and we
	// use 65000 bytes for the rest, that is predicate and the actual key.
	const maxKeySize = 65000

	for _, e := range edges {
		maxSizeForDataKey := maxKeySize - len(e.Attr)

		// seems reasonable to assume, the tokens for indexes won't be bigger than the value itself
		if len(e.Value) <= maxSizeForDataKey {
			continue
		}
		pred := x.NamespaceAttr(e.Namespace, e.Attr)
		update, ok := schema.State().Get(ctx, pred)
		if !ok {
			continue
		}
		// only string type can have large values that could cause us issues later
		if update.GetValueType() != pb.Posting_STRING {
			continue
		}

		storageVal := types.Val{Tid: types.TypeID(e.GetValueType()), Value: e.GetValue()}
		schemaVal, err := types.Convert(storageVal, types.TypeID(update.GetValueType()))
		if err != nil {
			return err
		}

		for _, tokenizer := range schema.State().Tokenizer(ctx, pred) {
			toks, err := tok.BuildTokens(schemaVal.Value, tok.GetTokenizerForLang(tokenizer, e.Lang))
			if err != nil {
				return fmt.Errorf("error while building index tokens: %w", err)
			}

			for _, tok := range toks {
				if len(tok) > maxSizeForDataKey {
					return errValueTooBigForIndex
				}
			}
		}
	}

	return nil
}

// validateCondValue checks that a cond string is a well-formed @if(...) or @filter(...)
// clause with balanced parentheses and no trailing content. This prevents DQL injection