[SERVER-71551] Follow up unit tests with overriden Cost Model in physical_rewriter_optimizer_test.cpp Created: 22/Nov/22  Updated: 05/Dec/22

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

Type: Task Priority: Major - P3
Reporter: Alexander Ignatyev Assignee: Backlog - Query Optimization
Resolution: Unresolved Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Assigned Teams:
Query Optimization
Participants:

 Description   

The new Cost Model introduces ABT nodes startup costs and makes IndexScan plans relatively more expansive then PhysicalScan on smaller collections. It laso makes index intersection plans with HashJoin and MergeJoin more expensive comparing to plain IndexScan plans which sometimes make IndexScan plan more preferable over index intersection plans.

As a result, we have added CostModel overrides to some of the Physical Rewriter unit tests.

This ticket is created to keep track of the overrides and can be resolved by a combination of the following:

  • the Cost Model is recalibrated
  • more stable optimizer (it can sometimes generate different plans on the same data and the same CostModel)
  • the tests are modified to force the desired plans

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