A change stream pipeline with empty field path match expression causes tripwire failure. For example:
db.test.aggregate([{$changeStream:{ fullDocument: 'updateLookup' }}, {"$match":{"":null}}])
The rewrite failure:
Error: command failed: {
"ok" : 0,
"errmsg" : "Failed to optimize pipeline :: caused by :: Unexpected empty path",
"code" : 5687201,
"codeName" : "Location5687201"
}
However, It is actually valid to have an empty field match expression. Removing $changeStream stage returns the results matching the expression in the collection:
db.test.insert({"": 123}) // not to be returned
db.test.insert({a: 10}) // to be returned
db.test.aggregate([{"$match":{"":null}}]) // returns {a: 10}
We need to fix and relax the restriction to allow empty field path matching.
- is related to
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SERVER-56872 Add optimization function to apply $match predicates on change streams events directly to oplog entry
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- Closed
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