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    <p>I think you have a conceptual problem with your schema. Remember that you always query for top level documents. The reason your query isn't working is because you're asking it to return <strong>top level</strong> documents where <strong>at least one</strong> of the elements has foo and <strong>at least one</strong> of the elements does not have a bar value. Note that both conditions need not apply on the same array element.</p> <p>You can do what you want in MongoDB using a $elemMatch :</p> <p><code>find({embedded:{$elemMatch:{foo:{$exists:true}, bar:{$exists:false}}}})</code> as demonstrated here :</p> <pre><code>&gt; db.test.save({embedded:[]}) &gt; db.test.save({embedded:[{foo:1}]}) &gt; db.test.save({embedded:[{bar:1}]}) &gt; db.test.save({embedded:[{foo:1, bar:1}]}) &gt; db.test.find({embedded:{$elemMatch:{foo:{$exists:true}, bar:{$exists:false}}}}) { "_id" : ObjectId("4f60c4d56fa40267a11d2f2c"), "embedded" : [ { "foo" : 1 } ] } </code></pre> <p>If "null" is a valid value for bar you can simply change it to :</p> <pre><code>&gt; db.test.save({embedded:[{foo:1, bar:null}]}) &gt; db.test.find({embedded:{$elemMatch:{foo:{$exists:true}, $or:[{bar:{$exists:false}}, {bar:null}]}}}) { "_id" : ObjectId("4f60c4d56fa40267a11d2f2c"), "embedded" : [ { "foo" : 1 } ] } { "_id" : ObjectId("4f60c52a6fa40267a11d2f30"), "embedded" : [ { "foo" : 1, "bar" : null } ] } </code></pre> <p>Now, in Morphia the $elemMatch is wrapped by the FieldEnd method "hasThisElement". I'm not that familiar with Morphia (I wrote and use my own mapper) but this should take a DBObject with the above clause as it's value and that should result in what you need to do. </p> <p>But again, this will return the top level documents that have elements in their embedded array that match these criteria. If you only want to return the matching elements you may have to turn your embedded structure in a top-level collection. It will be sufficient if your update only involves modifying the matching element(s) through the $ positional operator though :</p> <pre><code>db.test.update( {embedded:{$elemMatch:{foo:{$exists:true}, $or:[{bar:{$exists:false}}, {bar:null}]}}}, {$set:{'embedded.$.bar':"yay!"}} ) </code></pre>
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    1. USRemon van Vliet
    1. USRemon van Vliet
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    1. CO"you're asking it to return top level documents where at least one of the elements has foo and at least one of the elements does not have a bar value. Note that both conditions need not apply on the same array element." That's exactly what I want - they don't need to be on the same element. The above query fails if **any** of the bar fields has a value. And I want to get the top-level collection, that's sufficient.
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    2. COHm, in that case your requirement is a bit unclear to me. Can you extend your original post with sample data and what you want as the result of your query? Much like I did in my answer. It makes for a easier reading. And what do you mean by "failing"? Not returning results when it should? Throwing errors? Returning results when it shouldn't?
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      1. USRemon van Vliet
    3. COI've tried to clarified and added an example. And my anser below produces the desired result...
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