MongoDB indexed array { $gt: -Infinity } vs { $exists: true, $ne: [] }}

mongodb-array-not-empty.log

> db.users.find({'seen_events': { $gt: -Infinity }}).explain('executionStats')
{
	"queryPlanner" : {
		"plannerVersion" : 1,
		"namespace" : "dsl_tweet_database.users",
		"indexFilterSet" : false,
		"parsedQuery" : {
			"seen_events" : {
				"$gt" : -Infinity
			}
		},
		"winningPlan" : {
			"stage" : "FETCH",
			"inputStage" : {
				"stage" : "IXSCAN",
				"keyPattern" : {
					"seen_events" : 1
				},
				"indexName" : "seen_events_1",
				"isMultiKey" : true,
				"multiKeyPaths" : {
					"seen_events" : [
						"seen_events"
					]
				},
				"isUnique" : false,
				"isSparse" : false,
				"isPartial" : false,
				"indexVersion" : 2,
				"direction" : "forward",
				"indexBounds" : {
					"seen_events" : [
						"(-inf.0, inf.0]"
					]
				}
			}
		},
		"rejectedPlans" : [ ]
	},
	"executionStats" : {
		"executionSuccess" : true,
		"nReturned" : 0,
		"executionTimeMillis" : 1,
		"totalKeysExamined" : 0,
		"totalDocsExamined" : 0,
		"executionStages" : {
			"stage" : "FETCH",
			"nReturned" : 0,
			"executionTimeMillisEstimate" : 0,
			"works" : 1,
			"advanced" : 0,
			"needTime" : 0,
			"needYield" : 0,
			"saveState" : 0,
			"restoreState" : 0,
			"isEOF" : 1,
			"invalidates" : 0,
			"docsExamined" : 0,
			"alreadyHasObj" : 0,
			"inputStage" : {
				"stage" : "IXSCAN",
				"nReturned" : 0,
				"executionTimeMillisEstimate" : 0,
				"works" : 1,
				"advanced" : 0,
				"needTime" : 0,
				"needYield" : 0,
				"saveState" : 0,
				"restoreState" : 0,
				"isEOF" : 1,
				"invalidates" : 0,
				"keyPattern" : {
					"seen_events" : 1
				},
				"indexName" : "seen_events_1",
				"isMultiKey" : true,
				"multiKeyPaths" : {
					"seen_events" : [
						"seen_events"
					]
				},
				"isUnique" : false,
				"isSparse" : false,
				"isPartial" : false,
				"indexVersion" : 2,
				"direction" : "forward",
				"indexBounds" : {
					"seen_events" : [
						"(-inf.0, inf.0]"
					]
				},
				"keysExamined" : 0,
				"seeks" : 1,
				"dupsTested" : 0,
				"dupsDropped" : 0,
				"seenInvalidated" : 0
			}
		}
	},
	"serverInfo" : {
		"host" : "dsl-mongodb",
		"port" : 27017,
		"version" : "3.6.4",
		"gitVersion" : "d0181a711f7e7f39e60b5aeb1dc7097bf6ae5856"
	},
	"ok" : 1
}


> db.users.find({'seen_events': { $exists: true, $ne: [] }}).explain('executionStats')
{
	"queryPlanner" : {
		"plannerVersion" : 1,
		"namespace" : "dsl_tweet_database.users",
		"indexFilterSet" : false,
		"parsedQuery" : {
			"$and" : [
				{
					"seen_events" : {
						"$exists" : true
					}
				},
				{
					"$nor" : [
						{
							"seen_events" : {
								"$eq" : [ ]
							}
						}
					]
				}
			]
		},
		"winningPlan" : {
			"stage" : "FETCH",
			"filter" : {
				"$and" : [
					{
						"seen_events" : {
							"$exists" : true
						}
					},
					{
						"$nor" : [
							{
								"seen_events" : {
									"$eq" : [ ]
								}
							}
						]
					}
				]
			},
			"inputStage" : {
				"stage" : "IXSCAN",
				"keyPattern" : {
					"seen_events" : 1
				},
				"indexName" : "seen_events_1",
				"isMultiKey" : true,
				"multiKeyPaths" : {
					"seen_events" : [
						"seen_events"
					]
				},
				"isUnique" : false,
				"isSparse" : false,
				"isPartial" : false,
				"indexVersion" : 2,
				"direction" : "forward",
				"indexBounds" : {
					"seen_events" : [
						"[MinKey, MaxKey]"
					]
				}
			}
		},
		"rejectedPlans" : [
			{
				"stage" : "FETCH",
				"filter" : {
					"$and" : [
						{
							"$nor" : [
								{
									"seen_events" : {
										"$eq" : [ ]
									}
								}
							]
						},
						{
							"seen_events" : {
								"$exists" : true
							}
						}
					]
				},
				"inputStage" : {
					"stage" : "IXSCAN",
					"keyPattern" : {
						"seen_events" : 1
					},
					"indexName" : "seen_events_1",
					"isMultiKey" : true,
					"multiKeyPaths" : {
						"seen_events" : [
							"seen_events"
						]
					},
					"isUnique" : false,
					"isSparse" : false,
					"isPartial" : false,
					"indexVersion" : 2,
					"direction" : "forward",
					"indexBounds" : {
						"seen_events" : [
							"[MinKey, undefined)",
							"(undefined, [])",
							"([], MaxKey]"
						]
					}
				}
			}
		]
	},
	"executionStats" : {
		"executionSuccess" : true,
		"nReturned" : 1239016,
		"executionTimeMillis" : 107540,
		"totalKeysExamined" : 2929608,
		"totalDocsExamined" : 2785777,
		"executionStages" : {
			"stage" : "FETCH",
			"filter" : {
				"$and" : [
					{
						"seen_events" : {
							"$exists" : true
						}
					},
					{
						"$nor" : [
							{
								"seen_events" : {
									"$eq" : [ ]
								}
							}
						]
					}
				]
			},
			"nReturned" : 1239016,
			"executionTimeMillisEstimate" : 100264,
			"works" : 2929609,
			"advanced" : 1239016,
			"needTime" : 1690592,
			"needYield" : 0,
			"saveState" : 29956,
			"restoreState" : 29956,
			"isEOF" : 1,
			"invalidates" : 0,
			"docsExamined" : 2785777,
			"alreadyHasObj" : 0,
			"inputStage" : {
				"stage" : "IXSCAN",
				"nReturned" : 2785777,
				"executionTimeMillisEstimate" : 4707,
				"works" : 2929609,
				"advanced" : 2785777,
				"needTime" : 143831,
				"needYield" : 0,
				"saveState" : 29956,
				"restoreState" : 29956,
				"isEOF" : 1,
				"invalidates" : 0,
				"keyPattern" : {
					"seen_events" : 1
				},
				"indexName" : "seen_events_1",
				"isMultiKey" : true,
				"multiKeyPaths" : {
					"seen_events" : [
						"seen_events"
					]
				},
				"isUnique" : false,
				"isSparse" : false,
				"isPartial" : false,
				"indexVersion" : 2,
				"direction" : "forward",
				"indexBounds" : {
					"seen_events" : [
						"[MinKey, MaxKey]"
					]
				},
				"keysExamined" : 2929608,
				"seeks" : 1,
				"dupsTested" : 2929608,
				"dupsDropped" : 143831,
				"seenInvalidated" : 0
			}
		}
	},
	"serverInfo" : {
		"host" : "dsl-mongodb",
		"port" : 27017,
		"version" : "3.6.4",
		"gitVersion" : "d0181a711f7e7f39e60b5aeb1dc7097bf6ae5856"
	},
	"ok" : 1
}