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Type:
Question
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Resolution: Unresolved
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Priority:
Major - P3
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None
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Affects Version/s: 3.4.14, 3.6.3
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Component/s: None
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Labels:None
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Query Optimization
Just got acquainted with the $graphLookup aggregation, but it seems a little clunky for my main use case. So I have a combined question and/or feature request:
My use case is I want to fetch all descendants for a node in a tree structure. But I want them as plain documents. Thus I'm forced to something like:
db.nodes.aggregate([
{$match: {_id: 'STARTID'}},
{
$graphLookup: {
from: 'nodes',
startWith: '$_id',
connectFromField: 'children',
connectToField: '_id',
as: 'descendants',
},
},
{$unwind: '$descendants'},
{$replaceRoot: {newRoot: '$descendants'}}
])
It would be much more natural to me if the $graphLookup operator could operate without a starting collection, i.e. something like (I know this doesn't work now):
db.aggregate([
{
$graphLookup: {
from: 'nodes',
startWith: 'STARTID',
connectFromField: 'children',
connectToField: '_id'
},
}
])
So, is this something that can be done today in some similar fashion. Otherwise, it'd be nice to have.