[SERVER-39015] Make local reads for $lookup/$graphLookup (on unsharded collections) provide a shard version Created: 15/Jan/19  Updated: 27/Oct/23  Resolved: 07/Jul/21

Status: Closed
Project: Core Server
Component/s: Querying
Affects Version/s: None
Fix Version/s: None

Type: Improvement Priority: Major - P3
Reporter: Ian Boros Assignee: Katherine Wu (Inactive)
Resolution: Gone away Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Depends
depends on SERVER-38728 Allow pipeline with $lookup into a sh... Closed
Related
related to SERVER-27616 Fix $lookup/$graphLookup foreign coll... Backlog
Sprint: Query Optimization 2021-07-12
Participants:

 Description   

After SERVER-38728, if we find a collection is unsharded, we will just perform a local read on it (with no shard versioning). We should change this to deal with cases where the collection becomes sharded. Depending on how we do the "is the collection sharded" check, this may also be needed to deal with the case where the collection exists (and is not sharded) but is on a different shard.



 Comments   
Comment by Katherine Wu (Inactive) [ 07/Jul/21 ]

Closing as "Gone Away". After SERVER-45526, we don't do a local read and will target shards even if the 'from' collection is unsharded, since we might not be on the primary shard. This fixes the race condition where the 'from' collection suddenly becomes sharded.

Comment by James Wahlin [ 24/Jan/19 ]

As part of this work, we should determine whether we can address SERVER-32629. It is possible that we won't and will have to wait for delivery of SERVER-32198 to address but we should confirm.

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