[SERVER-66817] Re-enable featureFlagSbePlanCache Created: 26/May/22  Updated: 27/Oct/23  Resolved: 21/Jun/22

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

Type: Task Priority: Major - P3
Reporter: David Storch Assignee: David Storch
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-66583 Re-enable SBE as the default engine, ... Closed
Related
is related to SERVER-61314 Consolidate featureFlagSbePlanCache a... Closed
Sprint: QE 2022-06-27
Participants:

 Description   

The in-progress work from mihai.andrei@mongodb.com for SERVER-66583 will set the default value of featureFlagSbePlanCache to false. This makes sense because in release configurations we intend to only support SBE with pushed down $group and $lookup – but the SBE plan cache does not yet work with $group and $lookup queries.

This ticket tracks the work to re-enable the SBE plan cache feature flag by default (in the master branch only) once we are prepared to do so.



 Comments   
Comment by David Storch [ 21/Jun/22 ]

The situation here has changed. In order to get good SBE performance on a whole bunch of workloads we need the SBE plan cache enabled. But we also need the "applyClassicMatcher" work from SERVER-66814 in order to get good SBE performance. This poses a problem, because the "applyClassicMatcher" behavior cannot work with the SBE plan cache, and is inhibited when featureFlagSbePlanCache is enabled.

The SBE performance project will have to untie this gordian knot by fixing SBE native matching performance and deleting "applyClassicMatcher". In the process, the SBE performance project will also enable featureFlagSbeFull by default. For this reason, it makes sense to delete featureFlagSbePlanCache and consolidate it with featureFlagSbeFull. That work is planned under related ticket SERVER-61314. Resolving this ticket as "Gone Away".

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