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Using: mongod 2.4, mongod 2.5.6-pre, mongoS 2.5.6-pre
With a sharded collection (I used a hashed _id shard key)
Run an aggregation command with $explain
In the shell run:
db.runCommand({ "aggregate" : "<sharded_collection>" , "pipeline" : [ { "$project" : { "a" : 1 }} ] , "explain" : true})
{
"splitPipeline" : {
"shardsPart" : [
{
"$project" : {
"a" : true
}
}
],
"mergerPart" : [ ]
},
"shards" : {
"shard0000" : {
"host" : "precise64:27020",
"stages" : [
{
"$cursor" : {
"query" : {
},
"fields" : {
"a" : 1,
"_id" : 1
},
"plan" : {
"cursor" : "BasicCursor",
"isMultiKey" : false,
"scanAndOrder" : false,
"allPlans" : [
{
"cursor" : "BasicCursor",
"isMultiKey" : false,
"scanAndOrder" : false
}
]
}
}
},
{
"$project" : {
"a" : true
}
}
]
}
},
"code" : 0,
"ok" : 0,
"errmsg" : "exception: assertion src/mongo/bson/bsonobjbuilder.h:93"
}
The mongos logs:
014-02-18T12:59:46.835+0000 [conn1] pcursor finished on shard shard0001:precise64:27021, current connection state is { state: { conn: "(done)", vinfo: "mongo-java-driver-test.TEST @ 2|5||530354304b162de78a5666d2", cursor: { ok: 0.0, errmsg: "unrecognized field "cursor" }, count: 0, done: false }, retryNext: false, init: true, finish: true, errored: false }
2014-02-18T12:59:46.836+0000 [conn1] Assertion failure !e.eoo() src/mongo/bson/bsonobjbuilder.h 93
2014-02-18T12:59:46.839+0000 [conn1] 0xd61551 0xd0d089 0xcee7be 0x6d7811 0xb4fca9 0xc03fba 0xb4a18c 0xc28783 0xc01ccb 0x6dab41 0xd17fbb 0x7f2dedf31e9a 0x7f2ded244ccd
./bin/mongos(_ZN5mongo15printStackTraceERSo+0x21) [0xd61551]
./bin/mongos(_ZN5mongo10logContextEPKc+0x159) [0xd0d089]
./bin/mongos(_ZN5mongo12verifyFailedEPKcS1_j+0x17e) [0xcee7be]
./bin/mongos() [0x6d7811]
./bin/mongos(_ZN5mongo15dbgrid_pub_cmds15PipelineCommand3runERKSsRNS_7BSONObjEiRSsRNS_14BSONObjBuilderEb+0x1329) [0xb4fca9]
./bin/mongos(_ZN5mongo7Command22execCommandClientBasicEPS0_RNS_11ClientBasicEiPKcRNS_7BSONObjERNS_14BSONObjBuilderEb+0x2ba) [0xc03fba]
./bin/mongos(_ZN5mongo7Command20runAgainstRegisteredEPKcRNS_7BSONObjERNS_14BSONObjBuilderEi+0x32c) [0xb4a18c]
./bin/mongos(_ZN5mongo8Strategy15clientCommandOpERNS_7RequestE+0x303) [0xc28783]
./bin/mongos(_ZN5mongo7Request7processEi+0x6ab) [0xc01ccb]
./bin/mongos(_ZN5mongo21ShardedMessageHandler7processERNS_7MessageEPNS_21AbstractMessagingPortEPNS_9LastErrorE+0x71) [0x6dab41]
./bin/mongos(_ZN5mongo17PortMessageServer17handleIncomingMsgEPv+0x4fb) [0xd17fbb]
/lib/x86_64-linux-gnu/libpthread.so.0(+0x7e9a) [0x7f2dedf31e9a]
/lib/x86_64-linux-gnu/libc.so.6(clone+0x6d) [0x7f2ded244ccd]