Details
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New Feature
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Status: Closed
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Critical - P2
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Resolution: Done
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None
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Fully Compatible
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Query 2016-09-19, Query 2016-10-10
Description
I was looking at the optimizing aggregation pipelines docs page and didn't see this one listed.
This is only possible if the subsequent $match doesn't use any computed fields, but there could be a large win with regards to index usage if you could move the $match prior to a $project.
For example:
{ $project: { a: 1, b: 1, newField: { $add: ["$a", "$b"] } } },
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{ $match: { a : { $gt: 10 } }
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is the same as
{ $match: { a : { $gt: 10 } },
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{ $project: { a: 1, b: 1, newField: { $add: ["$a", "$b"] } } }
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because the $match is only using fields that exist in the original document.
Attachments
Issue Links
- is documented by
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DOCS-9547 Docs for SERVER-19153: Conditionally push $match before $project
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- Closed
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- is duplicated by
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SERVER-23991 $graphLookup should optimize with $match
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- Closed
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SERVER-4506 aggregation: optimize by pushing matches to earlier in a pipeline
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- Closed
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- is related to
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- Closed
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- Open
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- Closed
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- related to
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- Closed
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