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Type: Improvement
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Resolution: Unresolved
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Priority: Major - P3
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Affects Version/s: None
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Component/s: None
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Query Execution
We are interested in projecting a subset of fields from the post-image document in a changestream.
Testing showed (also see CLOUDP-91896) that performance only improves when the projection is smaller than some fraction of the total document size (as a function of network delay etc).
When most fields in the document are projected, there could be a 30% slowdown.
Is it possible to optimize changestream projection so that overheads for degenerate cases is minimized? Otherwise it is hard to determine whether or not Search can use this optimization for a certain collection.
Note that in this case, the projection only applies to fields nested under `fullDocument.*`, so it is possible to push the projection down to the query system (by a query optimization or by exposing new APIs)