As described in SERVER-81555, there are edge cases when an SBE plan for $lookup may not use an index, while the corresponding classic plan would. This task is to detect when that situation may arise, and avoid using SBE altogether in those cases. This is intended to be a simple, backportable change that works around the issue.
SERVER-81555 will track a complete, proper fix that allows SBE to use the correct index.
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SERVER-81555 $lookup on foreign field uses index in classic but not in SBE when collations do not match
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- Closed
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