Details
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New Feature
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Status: Closed
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Major - P3
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Resolution: Won't Fix
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None
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None
Description
Syntax
{$project: {
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fieldName: {
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$switch: {
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branches: [
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{
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case: <expression>,
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then: <expression>
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},
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…
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],
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default: <optional, expression>
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}
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}
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}}
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Examples
> db.coll.insert([
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{_id: 0, x: 0}
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{_id: 1, x: -1}
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{_id: 2, x: 2}
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]);
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> db.coll.aggregate([{
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$project: {
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z: {
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$switch: {
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branches: [
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{
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case: {$eq: ["$x", 0]},
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then: "Equal to zero."
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},
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{
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case: {$eq: [{$abs: "$x"}, 1]},
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then: "Equal to plus or minus one."
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},
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],
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default: "Something else."
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}
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}
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}
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}])
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{_id: 0, z: "Equal to zero."}
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{_id: 1, z: "Equal to plus or minus one."}
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{_id: 2, z: "Something else."}
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Notes
- Allows $project expressions to be written without convoluted $conds.
- If "case" does not return a boolean, the value will be coerced to a bool.
- Since each case does not have to be mutually exclusive, an input will enter the first branch it matches.
Errors - 'branches' is missing or not an array with at least one entry.
- An entry in 'branches' does not contain 'case'
- An entry in 'branches' does not contain 'then'
- If 'default' is not specified, and an input doesn't match, an error will be thrown.
Attachments
Issue Links
- depends on
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- Closed
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- is depended on by
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- Closed
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