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  1. C Driver
  2. CDRIVER-4224

Ignore read preference for $out/$merge on secondaries if any servers are pre-5.0

    • Type: Icon: Improvement Improvement
    • Resolution: Done
    • Priority: Icon: Major - P3 Major - P3
    • 1.21.0
    • Affects Version/s: None
    • Component/s: None
    • None
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      DRIVERS-1969:
      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.

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      DRIVERS-1969 : 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.

      This ticket was split from DRIVERS-1969, please see that ticket for a detailed description.

            Assignee:
            colby.pike@mongodb.com Colby Pike
            Reporter:
            dbeng-pm-bot PM Bot
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              Created:
              Updated:
              Resolved: