When using an accumulate in Drools, a rule is evaluated and triggered for a fact that wasn’t updated.
Here is the rule:
rule "WidgetsPerUser"
when
$user : User()
accumulate(
Widget ( checkIsUser($user) );
$widgetCount : sum(1)
)
then
System.out.println($user + " has " + $widgetCount + " widgets");
end
The idea is simple: count the number of Widget objects per User. checkIsUser() is a simple equality check, but represents a check that cannot use indexing.
Here is sample output from Drools 7.0.0.Final:
-- Calling fire all rules --
User5 has 10 widgets
User4 has 10 widgets
User3 has 10 widgets
User2 has 10 widgets
User1 has 10 widgets
Widget moved from User3 to User1
-- Calling fire all rules --
User5 has 10 widgets
User3 has 9 widgets
User1 has 11 widgets
Here we have 5 User facts inserted into memory, and all have a starting Widget count of 10. The first call for fireAllRules displays the correct prints, as all User facts are inserted into memory. Next is an update, where a Widget is moved from User3 to User1. The expected output is present, however User5 has no reason to be displayed as being updated.
To visually highlight the issue:
User5 has 10 widgets (User5 should NOT be triggered!)
(User4 is correctly ignored)
User3 has 9 widgets (User3 is correctly triggered)
(User2 is correctly ignored)
User1 has 11 widgets (User1 is correctly triggered)
The only way User5 differs from User2 or User4 is that it was the last user fact added, so why does it behave differently?
Is this extra evaluation expected? What purpose does it serve?
Note that the question is not about how to avoid or work around the extra trigger.
I dug around the drools core myself to get some answers. I found the following (in both versions 7.0.0 and 7.39.0):
In the method that evaluates the updates for the accumulate node PhreakAccumulateNode.doRightUpdates, just before the method doRightUpdatesProcessChildren (which is used for matching between left and right tuples), the following code is present:
// if LeftTupleMemory is empty, there are no matches to modify
if ( leftTuple != null ) {
if ( leftTuple.getStagedType() == LeftTuple.NONE ) {
trgLeftTuples.addUpdate( leftTuple ); //<----
}
doRightUpdatesProcessChildren( ARGS );
}
Based on this, regardless of there being a match within the tuples in the memory, if there is an update of a fact that is part of an accumulate, the first left tuple (in this case User5) will always be treated as being matched.
I took a look at another beta node JoinNode. The code for that node is similar to the AccumulateNode, however it is missing this additional update of the first left tuple, leading me to believe that it is accidentally added, and has no reason to be present.
Am I correct with this?
Related
I am new to Drools so please bear over with the terminology!
Can I make rule trigger even though an empty list is involved in the LHS?
I have the code below.
There are two rules. One rule that insert facts and another rule that work on facts.
Part of fact B is to hold a list of facts A.
If this list is not empty then I am able to work on fact B.
If this list is empty then I am not able to work on fact B.
How can I write the code so I am able to work on fact B even though the list is empty.
If I activate the line below "b.As.add(a);" then I can work on fact B.
If I deactivate the line below "b.As.add(a);" then I can work not on fact B.
declare A
nameA : String
end
declare B
nameB : String
As : java.util.ArrayList
end
rule "insertfacts"
when
then
A a = new A();
a.setNameA("A");
B b = new B();
b.setNameB("B");
b.As = new java.util.ArrayList();
b.As.add(a); // Only with this line rule checkfacts fires
insert( b );
end
rule "checkfacts"
when
$b : B();
$a : A() from $b.As;
then
// take action based on object $b
end
Thanks
Thomas S
To check if an object is present in working memory, you should use not() or exists() (depending on what you're trying to do.)
So your insert-facts rule should be like this:
rule "insertfacts"
when
not(B())
then
A a = new A();
a.setNameA("A");
B b = new B();
b.setNameB("B");
b.As = new java.util.ArrayList();
b.As.add(a); // Only with this line rule checkfacts fires
insert( b );
end
This way you won't end up with extra B instances because insertfacts will only trigger when B doesn't exist (so, once.)
To check for an empty list, you can do size == 0 as a check:
rule "As list is empty"
when
$b: B()
ArrayList( size == 0 ) from $b.As
then
// At this point you know that As is an empty list,
// so you can insert stuff if you want
end
Alternatively, if you want to check that a specific object is not in the list, you can use not memberOf.
rule "Some instance A is not in the As list"
when
$a: A() // the A instance we're trying to check
$b: B( $a not memberOf As )
then
// at this point As is a list of any size which doesn't contain the $a instance
end
Similarly there's memberOf for checking that the specific object is in the list:
rule "Some instance A is in the As list"
when
$a: A()
$b: B( $a memberOf As )
then
// As is a list of any size which DOES contain $a
end
Note that there are two complementary operators you could be using to check that something is or is not part of a list: memberOf and contains. They're roughly the same, just with the arguments in different orders. See this other question for more information about those two operators.
Of course, if you don't care at all about the contents of the As ArrayList, then just don't check anything against it in the "when" clause. If you're sure you'll never have a situation where it's undefined, you can even skip the null check.
rule "We don't care whether there's something in As"
when
$b: B( $as: As )
then
// at this point we have access to the variable $as which will be
// the arraylist; it may be empty, it may have stuff in it
end
... but you could always do a null check if you want to be safe:
$b: B( $as: As != null)
It was mentioned in a comment that you plan to write regular code in the "then" clause and loop through the list. Usually you don't want to do that -- if you just want to do work against the members of the list or a subset of the list (eg items of the list which meet certain criteria), Drools will implement the iteration out of the box for you.
As a simple example, let's say that you want to find all of the A instances inside of the list which have the name "PURCHASE" and update the name to be "VERIFIED_PURCHASE".
rule "Update PURCHASE to VERIFIED_PURCHASE"
when
B( $as: As != null )
$a: A( name == "PURCHASE" ) from $as
then
$a.name = "VERIFIED_PURCHASE"
end
(You could add an update call on the right hand side if it's important to reevaluate rule matches, but in this simple example it's not needed.)
What will happen here, and what's usually a little difficult for people new to Drools to wrap their heads around, is that Drools will internally iterate through the As array list and check each item to see if it matches the requested criteria (name == "PURCHASE"). For each item it finds that matches the criteria, it will trigger the right hand side.
So for this example, if As has 10 items and 3 are named "PURCHASE", this rule's consequences ("then" clause) will trigger 3 times, once per matched item.
If you need a collection of these matches on the right hand side, you can use collect or accumulate depending on how complex your use case is.
rule "Get all purchases"
when
B( $as: As != null )
$purchases: ArrayList() from collect( A( name == "PURCHASE" ) from $as )
then
// do something with $purchases here
end
Of course, you shouldn't then turn around and iterate through $purchases on the right hand side -- use the built-in way I showed previously.
The Drools engine is extremely good at optimizing performance; anything you put in the "when" clause gets optimized by Drools, which is why you want to do the iteration there (and let Drools leverage its own internal capabilities at that.)
The right hand side ("then" clause) is not optimized, so by putting the iteration and other logic on that side is going to make your rules perform worse in comparison. You may not notice the difference in a toy example like the ones we're working on in this question, but once you start processing hundreds or thousands of requests per minute, it will definitely start showing.
(I spent 10 years of my career supporting an embarrassingly huge collection of rules (scale is millions of rules) and I've never had the need to actually write a for-loop or any sort of iteration in the "then" clause. And the few places where I did find them as added by other engineers, I was able to remove them for non-negligible performance improvements. Let the framework do what it's good at.)
I am newbie to drools. Need understanding how to cascade filtered data from one condition to next one as shown below.
rule "rulename"
when
$var1 : MainObj(filter1)
$var2 : SubObj() from $var1.getSubObj // need all SubObj without any filter here for then clause.
$var3 : SubObj(conditions) from $var2 // Need a subset of SubObj for another then clause
then
$var2.doSomething()
$var3.doVar3Stuff()
end
How can I achieve that?
Continuation of my original post..
i have below rule computing statistics of a rule execution as below.
rule "myrule"
when
$a:wrapper(isActive("ruleName") && dataTypeCode.equals("typeCodeinDB"))
$total : Number() from accumulate($entity: MyObj(ObjAttribute=='testValue') from $a.getMyObj() , count( $entity ))
$filter: MyObj(ObjAttribute=="testValue" && ObjAttribute2.equals("ValidValue")) from $a.getMyObj()
then
$filter.addToResults($filter.getRuleConstituents(),1,drools.getRule().getName(),null); // Add data for insertion in DB at later stage
$filter.addPayloadExecution($a.dataTypeCode(),$a.getMyObj().toString(),$a.getMyObj().size()); //Total Count of MyObj
$filter.addRuleExecutions(drools.getRule().getName(), $total); // anotehr slice of data
end
Here.. i am computing two stats.. Total count of MYObj(), apply some filter for data validation and compute count of valid list ($filter is valid data)
When I run that code I am getting error as below
Exception executing consequence for rule "MyRule" in moneta.rules: [Error: $filter.addRuleExecutions(drools.getRule().getName(), $total): null]
[Near : {... $filter.addToResults($filter.get ....}]
^
[Line: 1, Column: 1]
Need advice on resolving this.
I can't tell if you're trying to change the data in one rule and make it visible in another, or if you're trying to do a single complex condition in a single rule. So I'll outline how both work.
Complex conditions
The pseudo-code in your rule indicates that you have a main object with a filter and a collection of sub-objects. You need to get a list of all sub-objects without a filter, and also to get a list of sub-objects that meet some sort of condition.
To collect these sublists, we have two available operations: accumulate and collect. Since you didn't give a real example, just some psuedo-code, I can't say for sure which is the correct one for you to use. The example I present below uses collect because it is appropriate for this use case. For more information about these operations, refer to the Drools documentation. I've linked to the section on operators; scroll down to see the details for collect and accumulate.
So imagine I have an app that is modeling a school, and my KindergartenClass object has a List of Student objects. In this case, KindergartenClass is the main object, and Student is the sub-object. My Students have names, ages, and an Allergies object that indicates food allergies. Students without Allergies have no allergy object. This is going to be the filter for the example rule -- finding the students without allergies.
The rule would then look like:
rule "EXAMPLE"
when
KindergartenClass( $students: students ) // $var1
// Find all students with no allergies, $var2
$var2: List() from collect( Student( allergies == null ) from $students )
// Find all students who are older than 5, $var3
$var3: List() from collect( Student( age > 5 ) from $students )
then
...
end
Obviously your right-hand-side would have to be adjusted because 'List' has no doSomething() and doVar3Stuff() methods. But without an actual example rule for what you're attempting I can't be more specific here.
You could get the individual students from the lists like this:
$studentWithoutAllergies: Student() from $var2
$studentOlderThan5: Student() from $var3
... but then your then-clause would trigger once for every single $studentWithoutAllergies and $studentOlderThan5. Most people don't want a cartesian product all elements in two lists and then having their consequences firing for each of those products.
Of course, you also talk about "cascading", though it's rather unclear what you mean. If you mean that you want $var3 to be a subset of what you found in $var2, then it's as simple as changing the from clause. So in the example I've been working with, if you actually want all students older than 5 who have no allergies, you can simply change the when clause to be:
// Find all students with no allergies, $var2
$var2: List() from collect( Student( allergies == null ) from $students )
// Find the subset of the non-allergy students who are older than 5, $var3
$var3: List() from collect( Student( age > 5 ) from $var2 )
Changing the data that triggers the rule
There are two keywords available for changing the data available to the left hand side (when clause): update and insert. Which one you use depends on what you're trying to do, and come with very different considerations in terms of performance.
When you ask Drools to fire a set of rules, it first goes through all of the rules and determines if the rule fires, given the data you've inputted. Basically it just goes through, in order, all of the when clauses and decides if the rule is activated or not. Then, once it has the sub-set of rules, in order, it goes through, one by one, executing the right hand side.
If you call update in your right hand side (then clause), then this process repeats: all rules are evaluated again, from the top, including the rule you just fired. If you call insert in your then clause, then the new data is put into working memory, and Drools re-evaluates all of the remaining rules in its execution list. (So, for example, if Drools had decided that rules A, B, C, and D met their when criteria, and B inserts a new fact into working memory, then C and D would be re-evaluated to make sure that they were still valid.)
This is how you'd use them:
rule "Example rule with Update"
when
$input: MyAwesomeInputObject(someValue == 0)
then
$input.setSomeValue(99);
$input.doSomeStuff();
update($input);
end
rule "Example rule with Insert"
when
Person(name == "Bob")
not( Age() )
then
Age age = new Age(18);
insert(age); // there is now an Age object in working memory
end
I'm not 100% familiar with your use case, but I'm going to assume you want to fire all of the filtering rules a second time after your initial rule fires, with the updated data. So I'd do something like this:
rule "rulename"
when
$var1 : MainObj(filter1)
$var2 : SubObj() from $var1.getSubObj // need all SubObj without any filter here for then clause.
$var3 : SubObj(conditions) from $var2 // Need a subset of SubObj for another then clause
then
$var2.doSomething();
$var3.doVar3Stuff();
update($var1); // update the var1 in working memory
end
I have no idea what your when clause is trying to do, since it doesn't appear to match the comments and the syntax is completely wonky. So only the right hand side (then clause) has been adjusted. I have added update($var1) so it will refire the rules with the new instance of $var1 that should have your changes in it.
Of course, once you start re-firing all rules, you run the risk of having rules loop. If this does happen, you will see spikes of CPU and apparent thread deadlocks (this is useful to alert on.) Note that there is a no-loop property, but it won't help when you're calling update.
Not the best title, but here's my challenge. I have a list on my page that can be sorted, and I want a Cypress test that checks that it works as expected. So imagine this test:
/* 1 */ cy.get('.list-item').eq(0).should('have.text', 'A');
/* 2 */ cy.get('.list-item').eq(-1).should('have.text', 'Z');
// Code that triggers sorting to change from asc to desc
/* 3 */ cy.get('.list-item').eq(0).should('have.text', 'Z');
/* 4 */ cy.get('.list-item').eq(-1).should('have.text', 'A');
Looks simple, but there's a slight delay when the sorting happens, so the UI isn't updated immediately.
I'm not sure if it's the cy.get or the eq function which causes it, but the problem is that line 3 "captures" the first element in the list, which is still 'A', and then tries to assert that the text is 'Z'. And when the list is reordered, this "captured" element doesn't actually change, it's just moved in the DOM, so the assertion still tries to assert that same element 'A', which in the DOM is actually the last element now, is 'Z', which it obviously isn't and shouldn't be.
If I insert a cy.wait(100) before 3, then it works as expected, but obviously I do not want to have a random wait in my test, so how do I solve this?
How do I check what the first and last elements are in a situation like this, when Cypress captures the DOM elements before they're reordered, without inserting an arbitrary wait? 😕
Actual case
Support app, showing a list of the 5 most recently viewed clients
Need to test that, when visiting for example number 3 in that list, it is moved to the top
The "code that triggers sorting" is actually a route navigation event:
There's a listener (React useEffect hook) on route changes.
When route changes, it updates the list of recently viewed client ids, which is stored in local storage.
When the list in local storage changes, the component showing the list first waits 750ms (so it's less confusing for user, but turned down to 10ms in Cypress tests), then updates (re-sorts) the list.
And since the list only contains ids, each tile will then async load the name and some more stuff to display on the list item.
So... the delay is actually more than just a UI update. There's routing, local storage and async requests involved too. 🎉
You need to merge cy.get(...) and .eq into a single selector to make sure it retries the assertion .should('have.text', 'Z') after resorting. Read about it https://on.cypress.io/retry-ability#Merging-queries - right now it grabs the list and then only retries .eq() command, which is too late. You could also rewrite your code to get the first and last elements using single .should(cb) https://on.cypress.io/should#Function - the example in the docs really fits your use case.
I am taking a wild shot here, but perhaps in the trigger to sort you could use then.
cy.get('.list-item').eq(0).should('have.text', 'A');
cy.get('.list-item').eq(-1).should('have.text', 'Z');
// Code that triggers sorting to change from asc to desc
cy.get("#id-to-sort").click().then(()=>{
cy.get('.list-item').eq(0).should('have.text', 'Z');
cy.get('.list-item').eq(-1).should('have.text', 'A');
})
I'm developing an event extension with recurring dates. Therefor, I have a recurring date pattern and copy the record for each date. So the record has a relation to itself:
- Main Event
-- N Child Events
Currently, I use the DataHandler method copyRecord, which works perfect. But this just copies the record, without mapping the relation.
- Main Event --> should have the count of children in the database
-- N Child Events --> should habe the relation to its parent main event
The DB should look like:
Event 1 (Main Event) | uid: 1 | event: 0 | recurring_children: 3 (count)
Event copy 1 | uid: 2 | event: 1 | recurring_children: 0
Event copy 2 | uid: 3 | event: 1 | recurring_children: 0
Event copy 3 | uid: 4 | event: 1 | recurring_children: 0
I tried several ways, but none without problems.
The following try sets the relation in the database, but creates more events (I guess, this loops and I have to build a condition to avoid filling the datamap with duplications):
public function processDatamap_afterDatabaseOperations(
$status,
$table,
$recordUid,
array $fields,
\TYPO3\CMS\Core\DataHandling\DataHandler $parentObject){
$event = BackendUtility::getRecord($table, $recordUid);
if ($status === 'update') {
/** #var \TYPO3\CMS\Core\DataHandling\DataHandler $tce */
$tce = \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance(\TYPO3\CMS\Core\DataHandling\DataHandler::class);
$tce->start(array(), array());
$overrides = [
'is_recurring_parent' => 0,
'is_recurring_child' => 1,
'recurring_weekdays' => '',
'recurring_period_end' => '0000-00-00',
'event' => $recordUid,
'title' => 'FOOBAR'
];
if ($event['is_recurring_parent']) {
$foobar = $tce->copyRecord('tx_technoseumevents_domain_model_event', $event['uid'], $event['pid'], false, $overrides);
}
T3 version 8.7
Sorry, my first time I'm using the datahandler for complex tasks. Maybe someone has a hint for me...
The recursiveness happening in the first place, indicates a problem with your architecture that might be worth addressing before this problem as it would solve it at the root cause instead of treating symptoms. Normally, a record should not relate to itself - but that said, recursiveness can happen in other ways and it might not be possible to avoid in your use case.
Advise for addressing the problem:
Consider adding a condition that prevents your code from being called on tables other than the one table you need to operate on. This alone could actually be why your copies recurse so that's number one to handle.
If possible, and if you are not concerned with short-circuiting things like changing the title TCA field for a record to prepend "Copy of", or causing the copy to be hidden, you can switch to copyRecord_raw. It takes slightly different arguments (you may have to refactor to pass some arguments as part of the overrides array, compared to calling copyRecord). Doing that will prevent hooks from being called on the children you copy.
You are using a nested DataHandler instance - it might be preferable to call that method on the $dataHandler instance in your example. The DataHandler maintains a copy stack, but (parts of) it will only work if you do things in the same instance and only for some particular hooks (i.e. the pre-type and not-global hooks).
Lastly, there exists a runtime cache entry which contains an array of records which have been copied. Although the utility methods that access and store entries in this cache entry are not publicly accessible - so you cannot call them from your hook class - you can read the array of entries, manipulate it and put it back to prevent recursive processing of the same record. See the method isNestedElementCallRegistered in DataHandler (https://github.com/TYPO3/TYPO3.CMS/blob/v8.7.17/typo3/sysext/core/Classes/DataHandling/DataHandler.php#L9034).
Final note: the after-database-operations hook may be called at times when you do not expect it. For example, if you copy a record and also move it (as in: the copy comes from the UI, not programmatically) the array you receive in $fieldArray may not be the final one (for example, pid may be an unexpected value). Not being aware of this and the peculiarities above might also increase the danger of unintentionally causing recursive operations.
EDIT: If you are using bi-directional relations in TCA then removing one side may also improve the situation. For example, each "date" doesn't necessarily have to be aware of which event it is associated with. Something to consider.
I'm creating a new view for a customized PoS module for my restaurant. It's a specific view for kitchen, already filtered to show just kitchen's related items of a PoS order.
Now I would like to show a particular series of product with the name starting with "#" in a field populated by a function side by side with the "standard" products. In fact I'm speaking of a set of instructions coded as products to be available on PoS and to suit my needs I decided to create kitchen instructions as a product (service). In my PoS there are 3 categories that are not products but instructions (ADD, SUBTRACT, ADDITIONAL NOTE).
A typical order will show as:
Product Quantity
[1007] Pom. Secchi 1
# + Búfala 1
# - Mussarela 1
[2002] Nutella banana 1
# + Mussarela 1
What I would like to archive is a view like:
Product Note Quantity
[1007] Pom. Secchi # + Búfala # - Mussarela 1
[2002] Nutella banana # + Mussarela 1
I need to select just the strings starting with the "#" between two internal code starting with "[code]" and this is the hard thing to do. I don't need to delete the values I "move" because I need the stock view when I print the receipt.
I will call this function using python (and psycopg2 on postgresql 9.4) with on_change or extending the workflow when an order is marked as "paid". I don't think if doing it directly in Python is viable.
I've tried with string_agg(,) but with bad results.
Any tips about what should be the correct path to start coding? Thanks.