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 the following integration tests: jstests/cqf/index_intersect.js and jstests/cqf/index_intersect.js.

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 generate different test data to force desired plans