Querying local cache first before querying server in Breeze JS

Question

I have an app using Breeze to query the data. I want to first check the local cache and then the server cache if no results are returned (I followed John Papa's SPA jumpstart course). However, I have found a flaw in my logic which I am not sure how to fix. Assuming I have 10 items that match my query.

Situation 1 (which works): I go to list page (Page A) displaying all 10. Hits server as cache is empty and adds all 10 to the cache. Then go to page displaying 1 result (Page B) which is found in the cache. So all good.

Situation 2 (the problem): I go to the page displaying 1 record first (Page B). Then I go to my list page (Page A) which checks the cache and finds 1 record and because of this line ( if (recordsInCache.length > 0)) it exits and only shows that 1 record.

I somehow need to know that there are more records on the server (9) that are NOT in the cache, ie. the total records for this query is actually 10, I have 1 therefore I have to hit server for the other 9.

Here is my query for Page A:

function getDaresToUser(daresObservable, criteria, forceServerCall)
{
    var query = EntityQuery.from('Dares')
        .where('statusId', '!=', enums.dareStatus.Deleted)
        .where('toUserId', '==', criteria.userId)
        .expand("fromUser, toUser")
        .orderBy('deadlineDate, changedDate');

    return dataServiceHelper.executeQuery(query, daresObservable, false, forceServerCall);
}

and here is my query for Page B (single item)

function getDare(dareObservable, criteria, forceServerCall)
{
    var query = EntityQuery.from('Dares')
        .expand("fromUser, toUser")
        .where('dareId', '==', criteria.dareId);

    return dataServiceHelper.executeQuery(query, dareObservable, true, forceServerCall);
}



function executeQuery(query, itemsObservable, singleEntity, forceServerCall)
{
    //check local cache first
    if (!manager.metadataStore.isEmpty() && !forceServerCall)
    {
        var recordsInCache = executeLocalQuery(query, itemsObservable, singleEntity);
        if (recordsInCache.length > 0)
        {
            callCompleted();
            return Q.resolve();
        }
    }

return manager.executeQuery(query)
        .then(querySucceeded)
        .fail(queryFailed);

}

function executeLocalQuery(query, itemsObservable, singleEntity)
{
    var recordsInCache = manager.executeQueryLocally(query);
    if (recordsInCache.length > 0)
    {
        processQueryResults(recordsInCache, itemsObservable, singleEntity, true);
    }
    return recordsInCache;
}

Any advice appreciated...

If you want to just hit the server for comparison purposes then at some point (either when loading up your app or when you hit the list page) call inlineCount to compare total on server vs what you already have like shown in this answer stackoverflow.com/questions/16390897/counts-in-breeze-js/… — PW Kad
Alternatively you may always fetch data for A before fetching the single entity for B getDaresForUser().then(getDare); (pseudo code). — pawel
Hmm - I was thinking about this - maybe ALL List pages should hit the server but all single entities should check the cache first? — Rodney

PW Kad PW Kad · Accepted Answer · 2013-08-12T13:37:43

If you want to just hit the server for comparison purposes then at some point (either when loading up your app or when you hit the list page) call inlineCount to compare total on server vs what you already have like shown in this answer stackoverflow.com/questions/16390897/counts-in-breeze-js/…

A way you can use this creatively while you are querying for the single record would be like this -

Set some variable in your view model or somewhere equal to total count

var totalCount = 0;

When you query the single record get the inline count -

var query = EntityQuery.from('Dares')
    .expand("fromUser, toUser")
    .where('dareId', '==', criteria.dareId)
    .inlineCount(true);

and set totalCount = data.inlineCount; Same thing when you get the total items list, just set the totalCount to inlineCount then too so you always know if you have all of the entities.

Querying local cache first before querying server in Breeze JS

2 Answers