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  1. Core Server
  2. SERVER-83614

$queue/$lookup pipeline can throw if database dropped at wrong time

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    • Type: Icon: Bug Bug
    • Resolution: Gone away
    • Priority: Icon: Major - P3 Major - P3
    • None
    • Affects Version/s: None
    • Component/s: None
    • Labels:
    • Query Optimization
    • ALL
    • QO 2023-12-11, QO 2023-12-25, QO 2024-01-08, QO 2024-01-22
    • 135

      An aggregation pipeline like

      [{$documents: [{x: 1, z: 'a\0'}, {clean: 2147483647, 'netstat': 'off'}, {x: 3, z: [1, 2, 3]}]},
 {$lookup: {from: 'test_coll', as: 'fullDocument', localField: 'x', foreignField: 'x'}}];

      should run on mongos if 'some_db.test_coll' does not exist, or on a shard otherwise. Currently, it will throw if someone drops the database at the wrong moment during the query execution.

      The reason for this is the deferred construction of CollectionRoutingInfo in ClusterAggregation::runAggregate().

      One possible solution would be to acquire CollectionRoutingInfo only once during query optimization and rewrite the pipeline accordingly. For instance, if we know 'some_db.test_coll' does not exist, we can remove the '$lookup' stage.

      When this is done, we should consider replacing the uassert with a tassert in runPipelineOnMongoS(), so that the fuzzer tests can discover unexpected issues.

            Assignee:
            henri.nikku@mongodb.com Henri Nikku
            Reporter:
            romans.kasperovics@mongodb.com Romans Kasperovics
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              Created:
              Updated:
              Resolved: