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POBreezejs - pattern for querying local cache
 

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    <p>I have a class called Item that is filtered by PeriodId. There are many periods - but we only need to look at one at a time. I want to present the user with an initial data load (say where PeriodId==1). I then want the user to be able to query/filter on other periods. </p> <p>If the user selects PeriodId==2, I want the entityManager to query the local cache, and if the data is there, return that data. If it's not in the local cache, I want it to query the server, and add the set where PeriodId==2 to the cache. If the user then clicks on PeriodId==1, that data should already be in the cache and not round-trip to the server. </p> <p>Using the code below, I am hitting the server every time I select a period (even if I just toggle back and forth). Is there a pattern that solves this... I do NOT know the primary keys here.</p> <pre><code>var getItems = function (myObservable, periodId, forceRemote) { var pId = periodId ? periodId : 1; var query = entityQuery.from('Item') .orderBy(orderBy.items) .where("PeriodId", "==", pId); if (!forceRemote) { var r = getLocal(query); if (r) { if (r.length &gt; 3) { myObservable(r); return Q.resolve(); } } } return manager.executeQuery(query) .then(querySucceeded) .fail(queryFailed); function querySucceeded(data) { if (myObservable) { myObservable(data.results); } } }; function getLocal(query) { try { return manager.executeQueryLocally(query); } catch(e) { // set was not found in local cache, return null - forcing trip to server return null; } } </code></pre> <p><strong>UPDATE:</strong> </p> <p>Incorporating Jay's suggestion, (I had to rename 'param' to 'pId', 'q' to 'query', reset the queryParamCache if forceRemote==true, and I had to prepend the FetchStrategy with 'breeze.' ):</p> <pre><code>var queryParamCache = {}; var getItems = function(myObservable, periodId, forceRemote) { if (forceRemote) { queryParamCache = {}; } var pId = periodId ? periodId : 1; var query = entityQuery.from('Item') .orderBy(orderBy.items) .where('PeriodId', '==', pId); var isInCache = queryParamCache[pId]; if (isInCache &amp;&amp; !forceRemote) { query = query.using(breeze.FetchStrategy.FromLocalCache); } else { queryParamCache[pId] = true; query = query.using(breeze.FetchStrategy.FromServer); } return manager.executeQuery(query) .then(querySucceeded) .fail(queryFailed); function querySucceeded(data) { rosterObservable(data.results); } }; function queryFailed(error) { var msg = 'Error retreiving data. ' + error.message; logError(msg, error); throw error; } </code></pre>
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