Mondrian parent-child hierarchy not working - parent-child

Question

Some issues to make mondrian work with a parent-child hierarchy.
My table structure is as follows (simplified, as the Category table is actually a MPTT):
RESPONSE QUESTION CATEGORY
-------------- ------------------- ----------
id ¡---> identifier (String) ¡---> id <---¡
question_id ___| category_id _____| parent_id _|
value (Measure) title name_en
My closure table is a simple setup: child_id, parent_id, distance (with the primary key being the tuple (child_id, parent_id) ).
My cube's schema is as follows:
<Cube cache="true"
defaultMeasure="Value" enabled="true" name="mycube">
<Table name="response" schema="public"/>
<Dimension foreignKey="question_id" name="Category">
<Hierarchy allMemberName="All Categories" hasAll="true"
primaryKey="identifier" primaryKeyTable="question">
<Join leftKey="category_id" rightKey="id">
<Table name="question"/>
<Table name="category"/>
</Join>
<!-- works fine with the category itself: <Level column="name" type="String" name="Category Name" table="category" uniqueMembers="true"/> -->
<Level column="id" name="Category ID"
nameColumn="name_en" nullParentValue="NULL"
parentColumn="parent_id" table="category"
type="Numeric" uniqueMembers="true">
<!-- type="Numeric" ordinalColumn="lft" parentColumn="parent_id" nullParentValue="NULL" -->
<Closure childColumn="child_id" parentColumn="parent_id">
<Table name="category_closure"/>
</Closure>
</Level>
</Hierarchy>
</Dimension>
<Measure aggregator="avg" caption="Value"
column="actual_value" formatString="#,###.00" name="Value"/>
</Cube>
Now, based on the mondrian FoodMart test pages, I have set up a simple jsp pages for my cube, which I want to use as a starting point for my tests. It has the following MDX:
select {[Measures].[Value]} ON COLUMNS,
{( [Category] )} ON ROWS
from [mycube]
The result it shows at first is "All Categories". When I try to drill down or hierarchize in the Categories, it returns nothing but [All Categories]. I have tried also with Descendants() to no avail.
Equally, when I try to list the members of Categories, it returns nothing.
I see that in the background it runs a query as follows to start the drilling down:
05/12/13 23:53:10,967 postgres: [3-1] LOG: execute : select
"category"."id" as "c0", "category"."name_en" as "c1" from "question"
as "question", "category" as "category" where "question"."category_id"
= "category"."id" and "category"."parent_id" IS NULL group by "category"."id", "category"."name_en" order by "category"."id" ASC
NULLS LAST
Obviously this query has an empty result because it joins question with root-level categories whilst only the leaves of my tree are attached some Questions.
It also shows that the closure table is not used here.
Any clue on what I can do to fix this?
Thanks ahead
lai

Answer 1

Following a few experiments, I shall conclude that my use case is probably not supported by Mondrian.
Here is the test I did to come to this conclusion:
- ensure I have 3 levels in my tree (level 0->2)
- create a fake question related to a root category (i.e. whose parent_id = NULL)
- create a response attached to this fake question
- at this stage, only level 0 and level 2 Category records have questions and responses related to them
- go ahead with a query
Here is the result I got in the logs:
14:37:09,082 WARN [SqlTupleReader] The level [Category].[Name] makes
use of the 'parentColumn' attribute, but a parent member for key 3 is
missing. This can be due to the usage of the NativizeSet MDX function
with a list of members form a parent-child hierarchy that doesn't
include all parent members in its definition. Using NativizeSet with a
parent-child hierarchy requires the parent members to be included in
the set, or the hierarchy cannot be properly built natively.
"key 3" relates to one of my level-2 records i.e. tree leaves (similar messages show for the other level-2 records).
Conclusion: not supported :-(
Enclosing the "working" schema below:
<Schema name="Foo">
<Cube name="Foo" caption="Cube to report on the Foo quizz dimensions" visible="true" defaultMeasure="Rating" cache="true" enabled="true">
<Table name="response" schema="public">
</Table>
<Dimension type="StandardDimension" visible="true" foreignKey="question_id" highCardinality="false" name="Category">
<Hierarchy name="Category" visible="true" hasAll="false" allMemberName="All Categories" primaryKey="identifier" primaryKeyTable="question">
<Join leftKey="category_id" rightKey="id">
<Table name="question" schema="public">
</Table>
<Table name="category" schema="public">
</Table>
</Join>
<Level name="Name" visible="true" table="category" column="id" nameColumn="name" ordinalColumn="tree_id" parentColumn="parent_id" nullParentValue="NULL" type="String" uniqueMembers="true" levelType="Regular" hideMemberIf="Never">
</Level>
</Hierarchy>
</Dimension>
<Measure name="Ratings" column="actual_value" formatString="#,###.00" aggregator="avg" caption="Ratings">
</Measure>
</Cube>
</Schema>