mongodb - Mongo DB concurrent findAndModify with increment operation -


if 2 agents run update query concurrently on mongo cluster, expected value of updateversion @ end?

db.task.findandmodify(     {         query:{"updateversion":21},         update:{$inc:{"updateversion":1}}     } );

if answer "23", there way have guaranteed read/write synchronized operation?

mongodb have faq section concurrent operations.

in case, write conflict might happen mongodb still try execute both commands:

a situation in 2 concurrent operations, @ least 1 of write, attempt use resource in way violate constraints imposed storage engine using optimistic concurrency control. mongodb transparently abort , retry 1 of conflicting operations.


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