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  1. Documentation
  2. DOCS-11226

MongoDB linearizable read concern restrictions

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      Could you add some details about Mongodb linearizable read concern documentation. It's not clear about:

      Linearizable read concern guarantees only apply if read operations specify a query filter that uniquely identifies a single document.

      Does it mean that i have to have unique index on fields that presented in query filter?

      Could you add better description or add some examples about this sentence, e.g.:

      1. I have collection test without unique index on A field.

      db.test.find({A:1}).readConcern("linearizable").maxTimeMS(10000)
      

      Is it linearizable and i can't get stale read? If answer yes, is it mean that there no reason to use linearizable read concern in reads by fileds which not presented in unique index?

      2. I have collection test with unique index on A field.

      db.test.ensureIndex({A:1}, {unique:true});
      db.test.find({A:1}).readConcern("linearizable").maxTimeMS(10000);
      

      Is it linearizable and i can't get stale read?

      3. I have collection test with unique index on A field.

      db.test.ensureIndex({A:1}, {unique:true});
      db.test.find({A:1, B:1}).readConcern("linearizable").maxTimeMS(10000);
      

      Is it linearizable and i can't get stale read?

      4. I have collection test without unique index on A field. But find method return only one document in result.

      db.test.find({A:1}).readConcern("linearizable").maxTimeMS(10000); //returned {_id:"someId", A:1}
      

      Is it linearizable and i can't get stale read?

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            Unassigned Unassigned
            DmitryZyr Dmitry Zyrianov
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              Created:
              Updated:
              1 year, 14 weeks, 2 days ago