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POUsing/Searching AsyncDataProvider with Objectify / Google App Engine
 

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  1. POUsing/Searching AsyncDataProvider with Objectify / Google App Engine
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    <p>I currently have an application which uses the activities/places and an AsyncDataProvider.</p> <p>Right now, everytime the activity loads up - it uses the request factory to retrieve the data (currently not a lot but will get very large coming up here soon) and passes it to the View to update the DataGrid. Before it is updated it is filtered based on a search box.</p> <p>Right now - I have implemented updating the DataGrid as follows: (this code isn't the prettiest)</p> <pre><code>private void updateData() { final AsyncDataProvider&lt;EquipmentTypeProxy&gt; provider = new AsyncDataProvider&lt;EquipmentTypeProxy&gt;() { @Override protected void onRangeChanged(HasData&lt;EquipmentTypeProxy&gt; display) { int start = display.getVisibleRange().getStart(); int end = start + display.getVisibleRange().getLength(); final List&lt;EquipmentTypeProxy&gt; subList = getSubList(start, end); end = (end &gt;= subList.size()) ? subList.size() : end; if (subList.size() &lt; DATAGRID_PAGE_SIZE) { updateRowCount(subList.size(), true); } else { updateRowCount(data.size(), true); } updateRowData(start, subList); } private List&lt;EquipmentTypeProxy&gt; getSubList(int start, int end) { final List&lt;EquipmentTypeProxy&gt; filteredEquipment; if (searchString == null || searchString.equals("")) { if (data.isEmpty() == false &amp;&amp; data.size() &gt; (end - start)) { filteredEquipment = data.subList(start, end); } else { filteredEquipment = data; } } else { filteredEquipment = new ArrayList&lt;EquipmentTypeProxy&gt;(); for (final EquipmentTypeProxy equipmentType : data) { if (equipmentType.getName().contains(searchString)) { filteredEquipment.add(equipmentType); } } } return filteredEquipment; } }; provider.addDataDisplay(dataGrid); } </code></pre> <p>Ultimately - what I would like to do is only load up the necessary data at first (the default page size in this application is 25).</p> <p>Unfortunately, to my current understanding, with Google App Engine there is no order to any of the Id's (one entry has an ID of 3 the next has an entry of 4203).</p> <p>What I'm wondering, what is the best way to go about retrieving a subset of data from Google App Engine when using Objectify? </p> <p>I was looking into using Offset and limit but another stack overflow post (http://stackoverflow.com/questions/9726232/achieve-good-paging-using-objectify) basically said this is inefficient.</p> <p>The best information I've found is the following link (http://stackoverflow.com/questions/7027202/objectify-paging-with-cursors). The answer here says to use Cursors but also says this is inefficient. I'm also using Request Factory so I will have to store the Cursor in my user Session (if that is incorrect please let me know).</p> <p>Currently since there isn't likely to be a lot of data (maybe 200 rows total for the next few months) I am just pulling back the entire set to the client as a temporary hack - I know this is the worst way to do it but would like to get input to the best way to do it before wasting my time implementing another hack solution. I am worried currently as it seems every single post i've read on doing this makes it seem like there's not really a solid way to do this. </p> <p>What i am also thinking about doing - currently my searching / page loading is lightning fast because all the data is already on the client side. I use a KeyUpEvent handler in the search box to filter the data - i don't think there is any way to keep this speed by making a call to the server - is there any accepted solution to this problem?</p> <p>Thank you very much</p>
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    1. USsean christe
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