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  1. PO
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    <p>I think what you are looking for is dot notation: <a href="http://docs.mongodb.org/manual/reference/glossary/#term-dot-notation" rel="nofollow">http://docs.mongodb.org/manual/reference/glossary/#term-dot-notation</a></p> <p>Question 1:</p> <blockquote> <ul> <li>How many blocks exist with a non-null/non-empty codes array?</li> </ul> </blockquote> <pre><code>db.videos.find( { 'video.blocks.codes.0' : { $exists : true } } ) </code></pre> <p>Effectively does the zero-th element of the array exist. For speed you create an index on <code>video.blocks.codes</code>. Also note that you will get back all of the video documents with at least 1 non-empty codes array within a block. To count the blocks you will have to do client side processing to remove the extra blocks.</p> <p>Question 2:</p> <blockquote> <ul> <li>How many blocks exist where the codes array matches a certain string in a given position?</li> </ul> </blockquote> <p>Very similar answer. For a position 3:</p> <pre><code>db.videos.find( { 'video.blocks.codes.3' : 'the magic code' } ) </code></pre> <p>Sorry I don't know Mongoid but hopefully you can translate the above.</p> <p>HTH - Rob.</p> <p>Edit:</p> <blockquote> <p>This doesn't work, because blocks is embedded and codes is an array within blocks.</p> </blockquote> <p>I don't think I understand the question then. The shell returns What I expect.</p> <p>Example from the shell (reformatted) - First the data:</p> <pre><code>&gt; db.test.find() { "_id" : ObjectId("51b7cfff0ccc6eb8b11c82b1"), "blocks" : [ { "index" : 1, "codes" : [ "a", "g", "c" ] }, { "index" : 2, "codes" : [ ] } ] } { "_id" : ObjectId("51b7d0300ccc6eb8b11c82b2"), "blocks" : [ { "index" : 1, "codes" : [ "x", "b", "d", "e" ] }, { "index" : 2, "codes" : [ "x", "b" ] } ] } { "_id" : ObjectId("51b7d0a50ccc6eb8b11c82b3"), "blocks" : [ { "index" : 1, "codes" : [ ] } ] } </code></pre> <p>First Query: Find all documents with a block with at least 1 code:</p> <pre><code>&gt; db.test.find( { 'blocks.codes.0' : { $exists : true } } ) { "_id" : ObjectId("51b7cfff0ccc6eb8b11c82b1"), "blocks" : [ { "index" : 1, "codes" : [ "a", "g", "c" ] }, { "index" : 2, "codes" : [ ] } ] } { "_id" : ObjectId("51b7d0300ccc6eb8b11c82b2"), "blocks" : [ { "index" : 1, "codes" : [ "x", "b", "d", "e" ] }, { "index" : 2, "codes" : [ "x", "b" ] } ] } </code></pre> <p>Second Query: Find all documents where the n'th code is a specific value. In this case I chose the second (index 1) is 'g'.</p> <pre><code>&gt; db.test.find( { 'blocks.codes.1' : "g" } ) { "_id" : ObjectId("51b7cfff0ccc6eb8b11c82b1"), "blocks" : [ { "index" : 1, "codes" : [ "a", "g", "c" ] }, { "index" : 2, "codes" : [ ] } ] } </code></pre>
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    1. POMongoDB: query array within embedded document
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    1. USRob Moore
    1. USRob Moore
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    1. COThis doesn't work, because `blocks` is embedded and `codes` is an array within `blocks`.
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      1. USMiguel Ping
    2. COI updated to show the queries working as I expected from the shell. Can you update the question with what you expect the results of the queries to be?
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      1. USRob Moore
 

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