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POMongo explicit/implicit AND behaving differently
 

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  1. POMongo explicit/implicit AND behaving differently
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    <p><strong>Basic question:</strong></p> <p>Are the following 2 queries meant to be equivalent?</p> <pre><code>(A) coll.find(k1:v1, k2:v2) // List of fields (B) coll.find($and: [{k1:v1}, {k2:v2}]) // $and the list of fields </code></pre> <p>If so, why do they show different behaviour? (see below). If not, how can I generate the former in C#?</p> <p><strong>Further discussion</strong></p> <p>I am indexing fields in a subdocument. Query (A) uses the indexes correctly but Query (B) does not.</p> <p>Here is some sample code (it will work directly in the mongo console):</p> <pre><code>{ _id : Guid ..other stuff.. Fields: { K1: V1, K2: V2 ...} } // Populate db.test.insert({_id:1,Fields:{K1:123,K2:456}}) db.test.insert({_id:2,Fields:{K1:456,K2:123}}) // Index on fields of subdocument db.test.ensureIndex({"Fields.K1": 1}) db.test.ensureIndex({"Fields.K2": 1})... // Execute some queries db.test.find({_id: {$lt: 20}, "$or": [{"Fields.K1": 123}, {"Fields.K2": 123}]}).explain() db.test.find({$and: [{_id: {$lt: 20}}, {"$or": [{"Fields.K1": 123}, {"Fields.K2": 123}]}]}).explain() </code></pre> <p>The first query uses the indexes as expected. The second does not.</p> <p><strong>Summary of questions</strong></p> <ol> <li>Are the two find() queries equivalent?</li> <li>If so, why is their behaviour different? If not, how are they different?</li> <li>How can I generate the find() without $and using the C# driver?</li> </ol> <p><strong>Edit</strong>--------</p> <p>For the record, the syntax I am using in C# is something along the lines of:</p> <pre><code>coll.find(Query.And([&lt;id query&gt;, &lt;fields query&gt;])); </code></pre> <p>Generating a QueryDocument manually does not work as it cannot contain multiple $or queries as $or is used as the key of a dictionary (and I need multiple $or in my actual query).</p>
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    1. USZaid Masud
    1. USmmmdreg
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      1. POMongo explicit/implicit AND behaving differently
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    1. COFrom the documentation: `MongoDB provides an implicit AND operation when specifying a comma separated list of expressions` Also check : http://stackoverflow.com/questions/9280540/mongo-index-not-being-used
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      1. POMongo explicit/implicit AND behaving differently
      1. USMustafa Genç
    2. COIf that is the case, why is the behaviour of an explicit AND different from an implicit AND? The question about generating a query without an explicit AND in C# driver still stands. I am currently doing coll.find(Query.And([<the id query>, <the Fields query>])).
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      1. USmmmdreg
 

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