MongoDB tricks to check performance

mongodb_tricks.txt

// Based on https://studio3t.com/knowledge-base/articles/mongodb-query-performance/
// THESE ARE THE Database.Collection
var scope = [
    "apps.appInstalls",
    "apps.apps"
]

// These are the operations to check
var generalOps = [
    "query", 
    "insert",
    "update",
    "remove"
] // all: "count", "distinct", "command", "geoNear", "getMore", "group", "insert", "mapReduce", "query", "remove", "update"


// Reset / Turn profiling on
/*
db.setProfilingLevel(0)
db.system.profile.drop()
db.createCollection("system.profile", { capped: true, size:100000000 } ) //100MB
db.setProfilingLevel(2)
*/

// Turn off profiling
/*
db.setProfilingLevel(0)
db.system.profile.drop()
*/

// Most recent queries
db.system.profile.find({
    "op": { $in: generalOps },
    "ns": { $in: scope }
})
.sort({ ts: -1 })
.pretty()

//Most recent updates
db.system.profile.find({
    "op": { $in: generalOps },
    "ns": { $in: scope },
    "command.u": { $exists: true }
})
.sort({ ts: -1 })
.pretty()

// Most recent inserts
db.system.profile.find({
    "op": { $in: generalOps },
    "ns": { $in: scope },
    "command.insert": { $exists: true }
})
.sort({ ts: -1 })
.pretty()

// Find all queries doing a COLLSCAN because there is no suitable index
db.system.profile.find({
    "planSummary": { $eq: "COLLSCAN" },
    "op": { $in: generalOps },
    "ns": { $in: scope }
})
.sort({ millis: -1 })
.pretty()

// Find the top ten slowest queries
db.system.profile.find({
    "op": { $in: generalOps },
    "ns": { $in: scope }
})
.sort({millis:-1})
.pretty()

// Top ten slowest commands/aggregations
db.system.profile.find({
    "op" : {$eq:"command"}
}, {
    "command.pipeline" : NumberInt(1),
    "millis": NumberInt(1)
})
.sort({millis:-1})
.pretty()

//Commenting your queries
db.modelClasses.find().comment("some comment");

// Display all queries with comments
db.system.profile.find({ "query.comment": "some comment" }, { query: 1 }).pretty()

// It is also possible to put a comment in the $match stage of an aggregation expression
db.modelClasses.aggregate([
    { $match : { "_meta.deleted": null } },
    { $comment: "some comment" },
    {$limit:10}
])