Minor - P4 If a projection computes `obj` only in terms of a meta field and another field `blergh` is computed in terms of value of `obj` IN THE SAME PROJECTION, then we will push down the meta-field-only computation of `obj`. This causes `obj` to be overwritten before we can compute `blergh` causing an incorrect calculation.
See the example below where `obj` is `obj` and `blergh` is `b`.
db.c.drop() db.d.drop() db.createCollection("c", {timeseries: {timeField: "t", metaField: "m"}}) db.c.insert({obj: {a: 3}, m: {}, t: new Date()}) db.d.insert({obj: {a: 3}, m: {}, t: new Date()}) db.d.aggregate([{$addFields: {obj: "$m", b: {$add: ["$obj.a", 1]}}}]) // Correct result { "_id" : ObjectId("6285641318f6a25daf333976"), "obj" : { }, "m" : { }, "t" : ISODate("2022-05-18T21:24:35.843Z"), "b" : 4 } db.c.aggregate([{$addFields: {obj: "$m", b: {$add: ["$obj.a", 1]}}}]) // incorrect result { "t" : ISODate("2022-05-18T21:24:57.873Z"), "m" : { }, "_id" : ObjectId("6285642918f6a25daf333978"), "obj" : { }, "b" : null }
- is related to
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SERVER-64102 $project field that references time-series meta field can be referenced by second $project field
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- Closed
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- Closed
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