Using BETWEEN together with date functions in WHERE clause 100x slower than InfiniDB

/* this is SLOW (27s) because 

   it combines BETWEEN and date function

*/

SELECT 

 SUM(impressions)

FROM

 action_date_hour

WHERE

 action_date BETWEEN CURRENT_DATE() AND CURRENT_DATE()

/* this is fast (0.23s) because no BETWEEN */

SELECT 

 SUM(impressions)

FROM

 action_date_hour

WHERE

 action_date >= CURRENT_DATE() 

  AND action_date <= CURRENT_DATE()

/* this is fast, no function in where */

SET @startDate=current_date();

SET @endDate=current_date();

SELECT 

 SUM(impressions)

FROM

 action_date_hour

WHERE

 action_date BETWEEN @startDate AND @endDate