
Type: Feature Request

Status: Resolved (View Workflow)

Priority: Major

Resolution: Done

Affects Version/s: 6.4.0.Final

Fix Version/s: 7.0.0.Beta2

Component/s: core engine

Labels:None

Docs QE Status:NEW

QE Status:NEW
Currently, when summing longs in an accumulate, we get something like this:
when ...

$t : Number(...) from accumulate(...,

sum($p.getLongWeight()))

then scoreHolder.addHard($t.longValue());

This has 3 problems:
 Loss of precision: the long sum `1881617265586265321L` will incorrectly return `1.88161726558626534E18`, so `13` too much! The BigDecimal sum of `0.09` and `0.01` will also be incorrect.
 Loss of performance: Summing with a Double total is significantly slower than summing with a Long total or an Integer total.
 Example complexity (minor, not all of us agree on this argument): the use of `Number` is an abstraction that doesn't bring any value to the use case. It's worthless complexity.
Solution proposal A) for 7.0 as discussed with Mario:
Based on the argument type to the sum function, the compiler selects a different sum function implementation. This is similar to java overloading mechanism, where `System.out.println(1)` selects a different method implementation than `System.out.println(2.0)`.
Support sum(Long):
when ...

$t : Long(...) from accumulate(...,

sum($p.getLongWeight()))

then scoreHolder.addHard($t);

and sum(BigDecimal):
when ...

$t : BigDecimal(...) from accumulate(...,

sum($p.getBigDecimalWeight()))

then scoreHolder.addHard($t);

and also support sum(Integer) and sum(BigInteger).
If this works well, we can consider it for other functions as well in a different jira issue.
Special case 1: sum(Number) should default to sum(Double) for backwards compatibility.
when ...

$t : Number(...) from accumulate(...,

sum($p.getNumberWeight()))

then scoreHolder.addHard($t.doubleValue());

Notsospecial case 2: to sum integers into a long total, the user should just use:
$t : Long(...) from accumulate(...,

sum((long) $p.getIntWeight()))

 causes

DROOLS2519 Implement specific numeric accumulate for min and max functions
 Resolved
 is duplicated by

DROOLS315 Support overloading of accumulate functions: Add int (or long) based sum's, int based avarage's, etc
 Open

DROOLS314 Build in accumulate functions are highly unreliable for long's and BigDecimals
 Open
 is related to

DROOLS1243 ClassCastException at runtime when trying to match "from" and a builtin accumulate function.
 Resolved