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  1. Core Server
  2. SERVER-48471

Hashed indexes may be incorrectly marked multikey and be ineligible as a shard key

    • Fully Compatible
    • ALL
    • v4.4, v4.2
    • Execution Team 2020-09-07, Execution Team 2021-01-11

      If an index build on a hashed index is concurrent with any collection writes, the index may be incorrectly marked multikey. As a result, this index can not be used as the shard key on a sharded collection. 


      Original title: shardCollection fails with "couldn't find valid index for shard key" despite index existing

      Original description:

      I'm attempting to shard a number of existing collections. They were all created and populated in a standalone mongod which has now been converted to a sharded cluster. Some of the collections have sharded successfully, others have failed with the above error. A possible cause of this was that the indexes were in the process of being created (with the background: true option) when the shardCollection command was first run, due to the script used not waiting for the background creation to complete.

        1. mongod.log
          74 kB
        2. mongod.log - config server
          4 kB
        3. mongos.log
          360 kB
        4. mongos.log.gz
          77.44 MB

            louis.williams@mongodb.com Louis Williams
            gavin.aiken@netcuras.com Gavin AIken
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