[security-dev] Picketlink 3 IDM - Counting of query results

[Marek Posolda]

On 05/12/12 23:21, Shane Bryzak wrote:
> On 12/06/2012 08:09 AM, Marek Posolda wrote:
>> Hi all,
>>
>> I have possible request for API change and hope it's not too late for
>> first IDM iteration.
>>
>> My suggestion is to have method on class IdentityStore with signature like:
>>
>> int countQueryResults(Map<QueryParameter,Object> parameters);
>>
>> in addition to current:
>>
>> List<IdentityType> fetchQueryResults(Map<QueryParameter,Object> parameters);
>>
>>
>> Example use-case could be: give me count of all users with first name "John"
>>
>> My motivation is, that for proper pagination support (searching
>> use-cases), you usually need to know total number of pages (records) and
>> then show searching results only from first page. Then user can browse
>> between pages (if more than one page is available). Something like
>> www.google.com is doing :-) Also we need to support this in GateIn portal.
>>
>> Note that having this method is redundant at first look, as you can
>> always obtain same results with: fetchQueryResults(queryParams).size()
>> But then we are obviously losing performance. For example in JPA (DB)
>> it's way more performant to call DB query like: select count(id) from
>> users;
>> instead of: select * from users;
>>
>> Also to properly support this, we may also need additional method on
>> IdentityQuery with signature like:
>>
>> int getResultCount();
> I have no problem adding this.
>
>>
>>
>> Also with respect to IdentityQuery, I am not sure how are information
>> about offset and limit propagated to IdentityStore? For example I have:
>> IdentityQuery query = IdentityManager().<User> createQuery(User.class);
>> query.setParameter(User.FIRST_NAME, "John");
>> query.setOffset(0);
>> query.setLimit(10);
>> query.getResultList();
>>
>> Calling of "getResultList" on last line will invoke
>> "fetchQueryResults(queryParams)" of configured IdentityStore. But how is
>> ensured that result from IdentityStore will return only first 10 records
>> as requested? So I think we can either:
>>
>> a) Change signature of method on IdentityStore to be:
>>
>> List<IdentityType> fetchQueryResults(Map<QueryParameter,Object>
>> parameters, int offset, int limit);
> We should probably just support this:
>
> List<IdentityType> fetchQueryResults(IdentityQuery query);
That would mean that we need additional getter methods on IdentityQuery 
interface, so that IdentityStore have access to all needed info. 
Something like:

Class<T> getIdentityType();

Map<QueryParameter, Object[]> getParameters();

int getOffset();

int getLimit();



Other approach is to have offset, limit and identityType available as 
additional queryParameters (like mentioned below in approach (b)) and on 
IdentityStore supports only this:

<T extends IdentityType> List<T> fetchQueryResults(Class<T> 
identityType, Map<QueryParameter,Object[]> parameters);

<T extends IdentityType> int 
countQueryResults(Map<QueryParameter,Object[]> parameters);

Marek

>
>
>
>>
>> b) Add QueryParameters for pagination support, which will be sent to
>> IdentityStore. Maybe we can have something like this on IdentityQuery
>> class:
>>
>> QueryParameter OFFSET = new QueryParameter() {};
>>
>> QueryParameter LIMIT = new QueryParameter() {};
>>
>> And something like this on DefaultIdentityQuery class:
>>
>>        @Override
>>        public IdentityQuery<T> setOffset(int offset) {
>>            parameters.put(IdentityQuery.OFFSET, offset);
>>            return this;
>>        }
>>
>>        @Override
>>        public IdentityQuery<T> setLimit(int limit) {
>>            parameters.put(IdentityQuery.LIMIT, limit);
>>            return this;
>>        }
>>
>> Currently I am not seeing any query parameters for pagination in codebase.
>>
>> WDYT?
>> Marek
>>
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