Re: [rules-dev] BUG: [5.3.0.Final] CollectSetAccumulateFunction should probably use IdentityHashMap internally
There are two types of facts - stated and justified. As explained in the
TMS section.
Justified facts are ALWAYS equality based, as it's the nature of TMS.
The other part of engine for stated facts is customizable and may work
in either equality mode or identity mode. Identity mode is default, as
it's the most common way java developers expect to work, knowledge
based engineers may prefer eqality mode.
We do discuss this in the maual. If it's clear, then please do help beef
up the docs on this. Fork the docs and submit a pull request, see:
http://www.athico.com/Getting_Involved/gettinginvolved.html
Mark
On 25/02/2012 19:41, SirMungus wrote:
By the way, while checking into various scenarios prompted by
Wolfgang's
response, I came up with a very interesting test program:
rule "Initialize"
salience 100
when
eval(true)
then
insert("one");
insert(new String("one"));
insertLogical("two");
insertLogical(new String("two"));
end
rule "Find strings"
salience 50
when
$s : String()
then
System.out.println("I found string: " + $s);
end
rule "Gather strings"
salience 50
when
accumulate(
$s : String(),
$sSet : collectSet( $s ),
$sList : collectList( $s ) )
then
System.out.println("Here is the set of all strings: " + $sSet);
System.out.println("Here is the list of all strings: " + $sList);
end
What would you expect that to output? How many "I found string: xxx" lines
would there be? How many entries in the "set of all strings"? How many
entries in the "list of all strings"?
For my part, I figured there would be four "I found string: xxx" lines, two
entries in the set, and four entries in the list.
I was very surprised to find the following output:
I found string: two
I found string: one
I found string: one
Here is the set of all strings: [two, one]
Here is the list of all strings: [one, one, two]
This strongly suggests that "insert" objects are held in an
identity-preserving structure, but that "insertLogical" objects are held in
an equals()-based structure.
I am glad for the identity-based handling of "insert" objects, especially
considering that all of my inserted objects come from "outside" the engine.
I would hate to see one of them fail to be considered by the rule engine.
I can almost see some usefulness for the equals() behavior of insertLogical
objects, but far more potential problems.
I think it's slightly dangerous that these behaviors differ and that it is
not, AFAIK, documented in a way that is clear to users of Drools.
--
View this message in context:
http://drools.46999.n3.nabble.com/BUG-5-3-0-Final-CollectSetAccumulateFun...
Sent from the Drools: Developer (committer) mailing list mailing list archive at
Nabble.com.
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