presto-main/src/main/java/io/prestosql/sql/planner/optimizations/AddLocalExchanges.java/Rewriter/visitTableWriter
class Rewriter:        @Override
        public PlanWithProperties visitTableWriter(TableWriterNode node, StreamPreferredProperties parentPreferences)
        {
            StreamPreferredProperties requiredProperties;
            StreamPreferredProperties preferredProperties;
            if (getTaskWriterCount(session) > 1) {
                requiredProperties = fixedParallelism();
                preferredProperties = fixedParallelism();
            }
            else {
                requiredProperties = singleStream();
                preferredProperties = defaultParallelism(session);
            }
            return planAndEnforceChildren(node, requiredProperties, preferredProperties);
        }