[rules-users] ConcurrentModificationException loading facts from db (Hibernate).
In my use case, I have ~ 200,000 rows in a table that I need lookup in order
to price an item. Rather than load the entire table into working memory,I'm
trying load the relevant rows (based on a matching criteria) and load those
as facts and then have my rules evaluate the loaded facts. Based on that
I've got the following rule :
rule "Load pricelist"
salience 10000
when
$priceUnit : PriceUnit()
not ( exists Pricelist( id.prodid == $priceUnit.prodid ) )
$unitPrices : ArrayList() from collect ( Pricelist() from
PricelistUtilities.getPriceLists($priceUnit.prodid) )
then
for( Pricelist priceList : (List<Pricelist>) $unitPrices ) {
insert (priceList);
}
end
In the rule above - 'PriceUnit' is the unit that I'm trying to price. And
'Pricelist' is the facts that I'm trying to fetch from a table based on the
prodid matching and inserting those into WM. The
PricelistUtilities.getPriceList returns a list of price list items that
match the 'Product id' (prodid). In the RHS, all I'm trying to iterate over
the list of pricelists and then insert those into WM.
When I execute the rule above, I can see that the rule is executing the
'select' to load pricelists :
Hibernate:
/*
from
PriceList
where
status = 'A'
and end_date >= current_date
and prodid = '010366'
and cover_grade = 'LF' */ select
pricelist0_.prodid as prodid1_,
pricelist0_.cover_grade as cover2_1_,
pricelist0_.cover_series as cover3_1_,
pricelist0_.cover_color as cover4_1_,
pricelist0_.division as division1_,
pricelist0_.location as location1_,
pricelist0_.list as list1_,
pricelist0_.start_date as start8_1_,
pricelist0_.end_date as end9_1_,
pricelist0_.timestamp as timestamp1_,
pricelist0_.status as status1_,
pricelist0_.sold_flag as sold12_1_,
pricelist0_.base_price as base13_1_,
pricelist0_.list_price as list14_1_,
pricelist0_.add_on as add15_1_,
pricelist0_.landed_frt as landed16_1_
from
catalog.pricelist pricelist0_
where
pricelist0_.status='A'
and end_date>=current_date
and prodid='123456'
However, I get an java.util.ConcurrentModificationException when the rule
fires :
org.drools.runtime.rule.ConsequenceException: rule: Load pricelist
at
org.drools.runtime.rule.impl.DefaultConsequenceExceptionHandler.handleException(DefaultConsequenceExceptionHandler.java:39)
at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:1101)
at org.drools.common.DefaultAgenda.fireNextItem(DefaultAgenda.java:1029)
at org.drools.common.DefaultAgenda.fireAllRules(DefaultAgenda.java:1251)
at
org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:737)
at
org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:701)
at
org.drools.impl.StatefulKnowledgeSessionImpl.fireAllRules(StatefulKnowledgeSessionImpl.java:218)
at com.generic.rules.utils.DroolsTest.main(DroolsTest.java:46)
Caused by: java.util.ConcurrentModificationException
at java.util.AbstractList$Itr.checkForComodification(AbstractList.java:372)
at java.util.AbstractList$Itr.next(AbstractList.java:343)
at
com.sample.Rule_Load_pricelist_0.defaultConsequence(Rule_Load_pricelist_0.java:7)
at
com.sample.Rule_Load_pricelist_0DefaultConsequenceInvoker.evaluate(Rule_Load_pricelist_0DefaultConsequenceInvoker.java:27)
at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:1091)
... 6 more
If I comment the check for existing PriceList Items 'not ( exists Pricelist(
id.prodid == $priceUnit.prodid ) )', then it works fine. But as soon as I
add the check back, it breaks.
Is this a bug or am I doing something wrong ?
Any help / insight will be appreciated.
Thanks in advance.
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