presto-base-jdbc/src/main/java/io/prestosql/plugin/jdbc/BaseJdbcClient.java/BaseJdbcClient/toPrestoType
class BaseJdbcClient:    @Override
    public Optional<ColumnMapping> toPrestoType(ConnectorSession session, Connection connection, JdbcTypeHandle typeHandle)
    {
        Optional<ColumnMapping> mapping = getForcedMappingToVarchar(typeHandle);
        if (mapping.isPresent()) {
            return mapping;
        }
        return jdbcTypeToPrestoType(session, typeHandle);
    }