Multiplying two columns in CASE statement overrides pushdown (Impala)

In the Impala translator, pushdown doesn't happen when two columns are multiplied in the THEN portion of a CASE statement with decimal data type.

//this should push down but does not
CASE WHEN column1 IS NOT NULL
THEN column1 * column2
ELSE column3 END

//but you can multiply the columns by a constant and it will push down
CASE WHEN column1 IS NOT NULL
THEN column1 * 34567
ELSE column3 END

//or

CASE WHEN column1 IS NOT NULL
THEN 34567 * column2
ELSE column3 END

//or casting to consistent datatypes with DECIMAL output
CASE WHEN column1 IS NOT NULL
THEN cast(column1 as DECIMAL ) * cast(column2 as DECIMAL )
ELSE cast(column3 as DECIMAL ) END

//BUT output it as double with the cast statement above changed and it does push down (so floating point works)
CASE WHEN column1 IS NOT NULL
THEN cast(column1 as double ) * cast(column2 as double)
ELSE cast(column3 as double) END

Source data types:
Column1 is DECIMAL
Column2 is BIGINT/LONG
Column3 is DECIMAL
Output column is DECIMAL