presto-orc/src/main/java/io/prestosql/orc/DictionaryCompressionOptimizer.java/DictionaryCompressionOptimizer/reset
class DictionaryCompressionOptimizer:    public void reset()
    {
        directConversionCandidates.clear();
        directConversionCandidates.addAll(allWriters);
        dictionaryMemoryBytes = 0;
        allWriters.forEach(DictionaryColumnManager::reset);
    }