Minor - P4 Using .explain() results in a log line like this:
2015-01-08T00:00:31.433+1100 I QUERY [conn4] command test.$cmd command: explain { explain: { find: "foo", filter: { a: 1.0 }, options: {} }, verbosity: "queryPlanner" } keyUpdates:0 numYields:0 reslen:383 0ms
But using $explain or ._addSpecial( "$explain", 1 ) results in this log line:
2015-01-08T00:02:58.169+1100 I QUERY [conn4] command test.foo command: isMaster { query: { a: 1.0 }, $explain: 1.0 } ntoreturn:0 keyUpdates:0 numYields:0 reslen:801 0ms
I don't know where "isMaster" comes from, but it has nothing to do with the query.
Also, using different ways of running explain shows different shell behavior (no linebreaks vs. pretty printed output).
$explain version
> db.foo.find({$query: {a:1}, $explain: true})
{ "queryPlanner" : { "plannerVersion" : 1, "namespace" : "test.foo", "parsedQuery" : { "a" : { "$eq" : 1 } }, "winningPlan" : { "stage" : "COLLSCAN", "filter" : { "a" : { "$eq" : 1 } }, "direction" : "forward" }, "rejectedPlans" : [ ] }, "executionStats" : { "executionSuccess" : true, "nReturned" : 1, "executionTimeMillis" : 0, "totalKeysExamined" : 0, "totalDocsExamined" : 1, "executionStages" : { "stage" : "COLLSCAN", "filter" : { "a" : { "$eq" : 1 } }, "nReturned" : 1, "executionTimeMillisEstimate" : 0, "works" : 3, "advanced" : 1, "needTime" : 1, "needFetch" : 0, "saveState" : 0, "restoreState" : 0, "isEOF" : 1, "invalidates" : 0, "direction" : "forward", "docsExamined" : 1 }, "allPlansExecution" : [ ] }, "serverInfo" : { "host" : "enter.local", "port" : 27017, "version" : "2.8.0-rc4", "gitVersion" : "3ad571742911f04b307f0071979425511c4f2570" } }
_addSpecial version
> db.foo.find({a:1})._addSpecial( "$explain", 1 )
{ "queryPlanner" : { "plannerVersion" : 1, "namespace" : "test.foo", "parsedQuery" : { "a" : { "$eq" : 1 } }, "winningPlan" : { "stage" : "COLLSCAN", "filter" : { "a" : { "$eq" : 1 } }, "direction" : "forward" }, "rejectedPlans" : [ ] }, "executionStats" : { "executionSuccess" : true, "nReturned" : 1, "executionTimeMillis" : 0, "totalKeysExamined" : 0, "totalDocsExamined" : 1, "executionStages" : { "stage" : "COLLSCAN", "filter" : { "a" : { "$eq" : 1 } }, "nReturned" : 1, "executionTimeMillisEstimate" : 0, "works" : 3, "advanced" : 1, "needTime" : 1, "needFetch" : 0, "saveState" : 0, "restoreState" : 0, "isEOF" : 1, "invalidates" : 0, "direction" : "forward", "docsExamined" : 1 }, "allPlansExecution" : [ ] }, "serverInfo" : { "host" : "enter.local", "port" : 27017, "version" : "2.8.0-rc4", "gitVersion" : "3ad571742911f04b307f0071979425511c4f2570" } }
.explain() version
> db.foo.find({a:1}).explain()
{
"queryPlanner" : {
"plannerVersion" : 1,
"namespace" : "test.foo",
"parsedQuery" : {
"a" : {
"$eq" : 1
}
},
"winningPlan" : {
"stage" : "COLLSCAN",
"filter" : {
"a" : {
"$eq" : 1
}
},
"direction" : "forward"
},
"rejectedPlans" : [ ]
},
"serverInfo" : {
"host" : "enter.local",
"port" : 27017,
"version" : "2.8.0-rc4",
"gitVersion" : "3ad571742911f04b307f0071979425511c4f2570"
},
"ok" : 1
}