Major - P3 The following command generates a plan that does not utilize the a_1_b_1_c_1 index.
> db.testcounthint.explain().count({a:1, b:2}, {hint: "a_1_b_1_c_1"})
{
"queryPlanner" : {
"plannerVersion" : 1,
"namespace" : "test.testcounthint",
"indexFilterSet" : false,
"parsedQuery" : {
"$and" : [
{
"a" : {
"$eq" : 1
}
},
{
"b" : {
"$eq" : 2
}
}
]
},
"winningPlan" : {
"stage" : "COUNT",
"inputStage" : {
"stage" : "COUNT_SCAN",
"keyPattern" : {
"b" : 1,
"a" : 1
},
"indexName" : "b_1_a_1",
"isMultiKey" : false,
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 1
}
},
"rejectedPlans" : [ ]
},
"serverInfo" : {
"host" : "grey.local",
"port" : 27017,
"version" : "3.2.5",
"gitVersion" : "34e65e5383f7ea1726332cb175b73077ec4a1b02"
},
"ok" : 1
}
Please note that without the explain, the correct plan is generated.
db.testcounthint.count({a:1, b:2}, {hint: "a_1_b_1_c_1"})
Additionally, note that the following command with explain generates the correct plan:
> db.testcounthint.explain().find({a:1,b:2}).hint("a_1_b_1_c_1").count()
{
"queryPlanner" : {
"plannerVersion" : 1,
"namespace" : "test.testcounthint",
"indexFilterSet" : false,
"parsedQuery" : {
"$and" : [
{
"a" : {
"$eq" : 1
}
},
{
"b" : {
"$eq" : 2
}
}
]
},
"winningPlan" : {
"stage" : "COUNT",
"inputStage" : {
"stage" : "COUNT_SCAN",
"keyPattern" : {
"a" : 1,
"b" : 1,
"c" : 1
},
"indexName" : "a_1_b_1_c_1",
"isMultiKey" : false,
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 1
}
},
"rejectedPlans" : [ ]
},
"serverInfo" : {
"host" : "grey.local",
"port" : 27017,
"version" : "3.2.5",
"gitVersion" : "34e65e5383f7ea1726332cb175b73077ec4a1b02"
},
"ok" : 1
}