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  1. Core Server
  2. SERVER-69416

Mongos fails explain cmd when database doesn't exist

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    • Type: Icon: Task Task
    • Resolution: Unresolved
    • Priority: Icon: Major - P3 Major - P3
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    • Cluster Scalability

      There is a difference in behavior between mongod and mongos when running explain command and db does not exist. 
      Mongod returns the explain plan, whereas mongos return a "database not found" error. 
      This can be seen in SERVER-68152 and https://jira.mongodb.org/browse/SERVER-68971 where explain_distinct.js fails when database doesn't exist:

       

      [js_test:explain_distinct] assert: command failed: {
[js_test:explain_distinct] "ok" : 0,
[js_test:explain_distinct] "errmsg" : "database test not found",
[js_test:explain_distinct] "code" : 26,
[js_test:explain_distinct] "codeName" : "NamespaceNotFound",
[js_test:explain_distinct] "$clusterTime" : {
[js_test:explain_distinct] "clusterTime" : Timestamp(1660233344, 7),
[js_test:explain_distinct] "signature" :
{ [js_test:explain_distinct] "hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="), [js_test:explain_distinct] "keyId" : NumberLong(0) [js_test:explain_distinct] }
[js_test:explain_distinct] },
[js_test:explain_distinct] "operationTime" : Timestamp(1660233344, 7)
[js_test:explain_distinct] 

       

      From:
      https://evergreen.mongodb.com/lobster/build/88ee203b553c2020128ed292340a9d9d/test/62f5268154f2484378a8aab0#bookmarks=0%2C114

            Assignee:
            backlog-server-cluster-scalability [DO NOT USE] Backlog - Cluster Scalability
            Reporter:
            adi.zaimi@mongodb.com Adi Zaimi
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              Created:
              Updated: