Question about type mistmatch of epl and esper

Question

The following are the program of epl on esper:

create schema
BarDataEvent(
             timestamp Date,
             openPrice BigDecimal, highPrice BigDecimal, lowPrice 
 BigDecimal, closePrice BigDecimal, volume double
           );
  
insert into BarDataEvent
select
Tick.lastDateTime as timestamp,
first(last) as openPrice,
max(last) as highPrice,
min(last) as lowPrice,
last(last) as closePrice, sum(vol) as tradingVolume
from Tick.win:time_batch(1 min)


  

Error reporting： Error starting statement: Nestable map type configuration encountered an unexpected property type name 'BigDecimal' for property 'lowPrice', expected java.lang.Class or java.util.Map or the name of a previously-declared Map type

I am not familiar with epl and esper, how to solve it?