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Type:
Improvement
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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: None
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Component/s: None
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Query Integration
With time-series data, you might want to store some metadata in separate collection. For example if each event is associated with a site (a location), you could have just the site name in each event, and the site details in separate collection:
> db.events.find()
{ ... meta: { site: 'A' }, ... }
{ ... meta: { site: 'B' }, ... }
...
> db.sites.find()
{ _id: 'A', ... }
{ _id: 'B', ... }
You would query it by doing a $lookup to pull the details into each event:
db.events.aggregate([
{$lookup: {
from: 'sites',
localField: 'meta.site',
foreignField: '_id',
as: 'meta.site_details',
}}
])
Since this $lookup only reads and writes metadata fields, we should be able to execute it once per bucket, before unpacking:
db.system.buckets.events.aggregate([
{$lookup: {
from: 'sites',
localField: 'meta.site',
foreignField: '_id',
as: 'meta.site_details',
}},
{$_internalUnpackBucket: {metaField: 'meta'}},
])
- related to
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- Backlog
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