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MongoDB分析查詢性能的步驟和代碼示例

更新時(shí)間：2026年03月26日 10:24:28 作者：Victor356

MongoDB提供了許多工具和命令,用于詳細(xì)分析查詢的性能表現(xiàn),下面給大家介紹MongoDB分析查詢性能的步驟和代碼示例,感興趣的朋友跟隨小編一起看看吧

1. 使用explain命令

explain 命令可以詳細(xì)描述查詢的執(zhí)行計(jì)劃，包括使用的索引、掃描的文檔數(shù)量等。

示例：基本explain使用

db.students.find({ studentId: 12345 }).explain("executionStats");

輸出示例及解讀

{
  "queryPlanner": {
    "plannerVersion": 1,
    "namespace": "school.students",
    "indexFilterSet": false,
    "parsedQuery": { "studentId": { "$eq": 12345 } },
    "winningPlan": {
      "stage": "FETCH",
      "inputStage": {
        "stage": "IXSCAN",
        "keyPattern": { "studentId": 1 },
        "indexName": "studentId_1",
        "direction": "forward",
        "indexBounds": { "studentId": [ "[12345, 12345]" ] }
      }
    },
    "rejectedPlans": []
  },
  "executionStats": {
    "executionSuccess": true,
    "nReturned": 1,
    "executionTimeMillis": 2,
    "totalKeysExamined": 1,
    "totalDocsExamined": 1,
    "executionStages": {
      "stage": "FETCH",
      "nReturned": 1,
      "executionTimeMillisEstimate": 0,
      "works": 2,
      "advanced": 1,
      "needTime": 0,
      "needYield": 0,
      "saveState": 0,
      "restoreState": 0,
      "isEOF": 1,
      "invalidates": 0,
      "docsExamined": 1,
      "alreadyHasObj": 0,
      "inputStage": {
        "stage": "IXSCAN",
        "nReturned": 1,
        "executionTimeMillisEstimate": 0,
        "works": 2,
        "advanced": 1,
        "needTime": 0,
        "needYield": 0,
        "saveState": 0,
        "restoreState": 0,
        "isEOF": 1,
        "invalidates": 0,
        "keyPattern": { "studentId": 1 },
        "indexName": "studentId_1",
        "isMultiKey": false,
        "multiKeyPaths": { "studentId": [] },
        "indexBounds": { "studentId": [ "[12345, 12345]" ] },
        "keysExamined": 1,
        "seeks": 1,
        "dupsTested": 0,
        "dupsDropped": 0
      }
    }
  },
  "serverInfo": {
    "host": "localhost",
    "port": 27017,
    "version": "4.4.6",
    "gitVersion": "22c124145fa3bfdaeafb3f6d1b5f3d4e8391fe86"
  }
}

關(guān)鍵指標(biāo)說明：

totalKeysExamined: 掃描的索引鍵數(shù)量。
totalDocsExamined: 掃描的文檔數(shù)量。數(shù)字越小越好。
executionTimeMillis: 查詢執(zhí)行時(shí)間，單位是毫秒。
winningPlan: 使用的執(zhí)行計(jì)劃，包括使用的索引。

2. 使用 MongoDB Profiler

MongoDB Profiler 可以記錄數(shù)據(jù)庫操作和慢查詢的詳細(xì)信息。

啟用 Profiler

db.setProfilingLevel(2);

查詢 Profiler 數(shù)據(jù)

db.system.profile.find().sort({ ts: -1 }).limit(1).pretty();

關(guān)閉 Profiler

db.setProfilingLevel(0);

示例輸出

{
  "op": "query",
  "ns": "school.students",
  "command": {
    "find": "students",
    "filter": { "studentId": 12345 },
    "projection": {},
    "sort": {}
  },
  "keysExamined": 1,
  "docsExamined": 1,
  "cursorExhausted": true,
  "numYield": 0,
  "locks": {
    "Global": { "acquireCount": { "r": 1 } },
    "Database": { "acquireCount": { "r": 1 } },
    "Collection": { "acquireCount": { "r": 1 } }
  },
  "nreturned": 1,
  "responseLength": 466,
  "millis": 2,
  "ts": ISODate("2021-07-20T14:45:14.467Z"),
  "client": "127.0.0.1",
  "appName": "MongoDB Shell",
  "allUsers": [],
  "user": ""
}

關(guān)鍵指標(biāo)說明：

keysExamined, docsExamined: 這些指標(biāo)與explain命令的輸出類似。
millis: 查詢執(zhí)行時(shí)間，單位是毫秒。
nreturned: 返回的文檔數(shù)量。

3. 使用db.currentOp()命令

db.currentOp() 可以查看當(dāng)前正在運(yùn)行的操作。

示例：查看當(dāng)前操作

db.currentOp();

示例輸出

{
  "inprog": [
    {
      "opid": 12345,
      "active": true,
      "secs_running": 2,
      "microsecs_running": NumberLong(2000000),
      "op": "query",
      "ns": "school.students",
      "query": { "studentId": 12345 },
      "client": "127.0.0.1:50731",
      "desc": "conn123",
      "threadId": "0x7fd4e7bfb700",
      "connectionId": 123,
      "waitingForLock": false,
      "lockStats": { "Global": { "acquireCount": { "r": NumberLong(1) } } }
    }
  ]
}

關(guān)鍵指標(biāo)說明：

secs_running: 查詢已運(yùn)行的時(shí)間，單位是秒。
op: 當(dāng)前正在執(zhí)行的操作類型。
query: 正在執(zhí)行的查詢。

4. 使用 Index Usage Statistics

查看索引的使用情況，識(shí)別未使用的索引。

示例：查看索引使用情況

db.students.aggregate([
  { $indexStats: {} }
]);

示例輸出

[
  {
    "name": "studentId_1",
    "key": { "studentId": 1 },
    "host": "localhost:27017",
    "accesses": {
      "ops": 123,
      "since": ISODate("2021-07-01T00:00:00Z")
    }
  }
]

關(guān)鍵指標(biāo)說明：