MongoDb Failing to Build Index - Caught exception during index builder initialization

Question

When I try to build a compound index on my Atlas server, it shows no error but then the index doesn't get built.

Trying it via shell, I get the following:

MongoDB Enterprise mongos> db.myCollection.createIndex( {"user_id": "hashed", "identifier": 1, "timestamp": 1} )
{
    "raw" : {
        "atlas-lgwyih-shard-1/atlas-lgwyih-shard-01-00.kqohn.mongodb.net:27017,atlas-lgwyih-shard-01-01.kqohn.mongodb.net:27017,atlas-lgwyih-shard-01-02.kqohn.mongodb.net:27017" : {
            "ok" : 0,
            "errmsg" : "Caught exception during index builder initialization my-db.myCollection (c22f2095-1221-43cd-80af-13f2fb3afaff): 1 provided. First index spec: { ns: \"my-db.myCollection\", v: 2, key: { user_id: \"hashed\", identifier: 1.0, timestamp: 1.0 }, name: \"user_id_hashed_identifier_1_timestamp_1\" }",
            "code" : 16763,
            "codeName" : "Location16763"
        }
    },
    "code" : 16763,
    "codeName" : "Location16763",
    "ok" : 0,
    "errmsg" : "Caught exception during index builder initialization my-db.myCollection (c22f2095-1221-43cd-80af-13f2fb3afaff): 1 provided. First index spec: { ns: \"my-db.myCollection\", v: 2, key: { user_id: \"hashed\", identifier: 1.0, timestamp: 1.0 }, name: \"user_id_hashed_identifier_1_timestamp_1\" }",
    "operationTime" : Timestamp(1596400670, 1),
    "$clusterTime" : {
        "clusterTime" : Timestamp(1596400671, 4),
        "signature" : {
            "hash" : BinData(0,"oh8t17bzKDwsyxv4WzK5suDFP9U="),
            "keyId" : NumberLong("6855996587379516447")
        }
    }
}

I only have the default index on the collection so far:

MongoDB Enterprise mongos> db.getCollection("myCollection").getIndexes()
[
    {
        "v" : 2,
        "key" : {
            "_id" : 1
        },
        "name" : "_id_",
        "ns" : "my-db.myCollection"
    }
]

Note that I want this index in this order because I want to shard the collection with the shard key being on hashed User IDs.

What is causing this error?

ShaneOH · Accepted Answer · 2020-08-03 12:32:32Z

3

Ah, for some reason after hours of banging my head against the wall I just thought to confirm whether it's possible to create a compound index with one type being hashed. Turns out this is causing the error -- wish that error message was clearer on that!

Also, this is now supported in version 4.4 as pointed out in the comments below!

edited Aug 3, 2020 at 12:32

answered Aug 2, 2020 at 20:46

ShaneOH

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1 Comment

D. SM Over a year ago

This is supported in 4.4 server but not in previous versions.

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