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How do MongoDB multi-keys sort?

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问题 In MongoDB, a field can have multiple values (an array of values). Each of them is indexed, so you can filter on any of the values. But can you also "order by" a field with multiple values and what is the result? Update: > db.test.find().sort({a:1}) { "_id" : ObjectId("4f27e36b5eaa9ebfda3c1c53"), "a" : [ 0 ] } { "_id" : ObjectId("4f27e3845eaa9ebfda3c1c54"), "a" : [ 0, 1 ] } { "_id" : ObjectId("4f27df6e5eaa9ebfda3c1c4c"), "a" : [ 1, 1, 1 ] } { "_id" : ObjectId("4f27df735eaa9ebfda3c1c4d"), "a"

How to use/create boost::multi_index?

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问题 Can someone explain to me in detail how to create a multi index map using boost::multi_index ? I saw many examples online and also the boost page, but I could not understand it. I would want to map class object pointer by multiple int/longs as keys. Can someone please help me with understanding this? I have a class X and multiple properties of the class which are long long , long , int , int . I want to store properties long long , long , int , int as keys to map to -> <pointer to X>. I want

mongodb multikey index seems like not being used when sort

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问题 Let's assume that I have tx_collection which has 3 documents like below { "block_number": 1, "value": 122 "transfers": [ { "from": "foo1", "to": "bar1", "amount": 111 }, { "from": "foo3", "to": "bar3", "amount": 11 }, ] }, { "block_number": 2, "value": 88 "transfers": [ { "from": "foo11", "to": "bar11", "amount": 33 }, { "from": "foo22", "to": "bar22", "amount": 55 }, ] }, { "block_number": 3, "value": 233 "transfers": [ { "from": "foo1", "to": "bar1", "amount": 33 }, { "from": "foo3", "to":

Multi-key Indexing on an Entire Array

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问题 MongoDB's docs explain multi-key indexing. Consider this comment document. { "_id": ObjectId(...) "title": "Grocery Quality" "comments": [ { author_id: ObjectId(...) date: Date(...) text: "Please expand the cheddar selection." }, { author_id: ObjectId(...) date: Date(...) text: "Please expand the mustard selection." }, { author_id: ObjectId(...) date: Date(...) text: "Please expand the olive selection." } ] } The docs explain that it's possible to index on the comments.text , or any comments

How do MongoDB multi-keys sort?

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In MongoDB, a field can have multiple values (an array of values). Each of them is indexed, so you can filter on any of the values. But can you also "order by" a field with multiple values and what is the result? Update: > db.test.find().sort({a:1}) { "_id" : ObjectId("4f27e36b5eaa9ebfda3c1c53"), "a" : [ 0 ] } { "_id" : ObjectId("4f27e3845eaa9ebfda3c1c54"), "a" : [ 0, 1 ] } { "_id" : ObjectId("4f27df6e5eaa9ebfda3c1c4c"), "a" : [ 1, 1, 1 ] } { "_id" : ObjectId("4f27df735eaa9ebfda3c1c4d"), "a" : [ 1, 1, 2 ] } { "_id" : ObjectId("4f27df795eaa9ebfda3c1c4e"), "a" : [ 2, 1, 2 ] } { "_id" : ObjectId(