Details
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New Feature
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Status: Backlog
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Major - P3
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Resolution: Unresolved
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None
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None
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None
Description
In many cases, it would be useful to construct an object from an array of key/value pairs. The new expression should be designed to work with the expression requested in SERVER-18794. For example, we could add an $arrayToObject expression, which could do the following:
db.foo.drop();
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db.foo.insert({
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myArray: [ ["price", 200], ["item", "mango"] ], |
document: {x: 1, y: 2, z: 2},
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docs: [
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{email: "charlie", count: 4, blah: "foo"}, |
{email: "eliot", count: 500, blah: "bar"}, |
]
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});
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db.foo.aggregate([{
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$project: {
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convertedFrom2dArray: {$arrayToObject: "$myArray"}, |
noOp: {$arrayToObject: {$objectToArray: "$document"}}, |
aggregated: {$arrayToObject: {$zip: ["$docs.email", |
"$docs.count"]}}} |
}
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}]);
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// Output:
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{
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_id: xxx,
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convertedFrom2dArray: {"price": 200, "item": "mango"}, |
noOp: {x: 1, y: 2, z: 2},
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aggregated: {charlie: 4, eliot: 500},
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}
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The expression should accept an array of pairs either represented as
- an array of two-element arrays (like [ ["price", 200], ["item", "mango"] ] above), or
- an array of two-field objects with key names k and v.
In the latter case, the expression would permit conversion of [{k: "price", v: 200}, {k: "item", v: "mango"}] to {price: 200, item: "mango"}.
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- is depended on by
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- Closed
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