Question

I am using FindAndModify in MongoDB in several concurrent processes. The collection size is about 3 million entries and everything works like a blast as long as I don’t pass a sorting option (by an indexed field). Once I try to do so, the following warning is spawned to the logs:

warning: ClientCursor::yield can't unlock b/c of recursive lock ns: test_db.wengine_queue top: 
{ 
opid: 424210, 
active: true, 
lockType: "write", 
waitingForLock: false, 
secs_running: 0, 
op: "query", 
ns: "test_db", 
query: { 
    findAndModify: "wengine_queue", 
    query: { 
            locked: { $ne: 1 }, 
            rule_completed: { $in: [ "", "0", null ] }, 
            execute_at: { $lt: 1324381363 }, 
            company_id: 23, 
            debug: 0, 
            system_id: "AK/AK1201" 
        }, 
    update: { 
            $set: { locked: 1 } 
        }, 
    sort: { 
            execute_at: -1 
        } 
}, 
client: "127.0.0.1:60873", 
desc: "conn", 
threadId: "0x1541bb000", 
connectionId: 1147, 
numYields: 0 
}

I do have all the keys from the query indexed, here they are:

PRIMARY> db.wengine_queue.getIndexes()
[
{
    "v" : 1,
    "key" : {
        "_id" : 1
    },
    "ns" : "test_db.wengine_queue",
    "name" : "_id_"
},  
{
    "v" : 1,
    "key" : {
        "system_id" : 1,
        "company_id" : 1,
        "locked" : 1,
        "rule_completed" : 1,
        "execute_at" : -1,
        "debug" : 1
    },
    "ns" : "test_db.wengine_queue",
    "name" : "system_id_1_company_id_1_locked_1_rule_completed_1_execute_at_-1_debug_1"
},  
{
    "v" : 1,
    "key" : {
        "debug" : 1
    },
    "ns" : "test_db.wengine_queue",
    "name" : "debug_1"
},
{
    "v" : 1,
    "key" : {
        "system_id" : 1
    },
    "ns" : "test_db.wengine_queue",
    "name" : "system_id_1"
},
{
    "v" : 1,
    "key" : {
        "company_id" : 1
    },
    "ns" : "test_db.wengine_queue",
    "name" : "company_id_1"
},
{
    "v" : 1,
    "key" : {
        "locked" : 1
    },
    "ns" : "test_db.wengine_queue",
    "name" : "locked_1"
},
{
    "v" : 1,
    "key" : {
        "rule_completed" : 1
    },
    "ns" : "test_db.wengine_queue",
    "name" : "rule_completed_1"
},
{
    "v" : 1,
    "key" : {
        "execute_at" : -1
    },
    "ns" : "test_db.wengine_queue",
    "name" : "execute_at_-1"
},
{
    "v" : 1,
    "key" : {
        "thread_id" : 1
    },
    "ns" : "test_db.wengine_queue",
    "name" : "thread_id_1"
},
{
    "v" : 1,
    "key" : {
        "rule_id" : 1
    },
    "ns" : "test_db.wengine_queue",
    "name" : "rule_id_1"
}
]

Is there any way around this?

Answer 1

For those interested — I had to create a separate index ending with the key that the set is to be sorted by.