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  1. Java Driver
  2. JAVA-4380

Fix server selection logic for $out/$merge on secondary

    • Type: Icon: Improvement Improvement
    • Resolution: Fixed
    • Priority: Icon: Major - P3 Major - P3
    • 4.4.0
    • Affects Version/s: None
    • Component/s: Query Operations
    • Labels:
    • Not Needed

      In mongodb/specifications@747b748, the rules were applying a read preference for aggregations using $out and $merge was changed. Previously, drivers were instructed to attempt using the read preference and only fall back to a primary if a pre-5.0 secondary was selected.

      This was changed to require drivers to always disregard the read preference if there is any evidence of a pre-5.0 server. If there are either no available servers or all servers are 5.0+ (or load balanced, where we assume 5.0+), drivers can utilize the read preference.

      Spec tests have not been changed, as this clarification really only changes behavior for mixed version clusters or a replica set consisting of a single pre-5.0 primary, neither of which are tested.

            jeff.yemin@mongodb.com Jeffrey Yemin
            jeff.yemin@mongodb.com Jeffrey Yemin
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