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MongoDB实战读书笔记（一）：JavaScript shell操作MongoDB

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08/10
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1 基本增删改查

  • 基本概念：
    • 数据库：同关系型数据库
    • 集合：类似关系型数据库的表
    • 文档：类似关系型数据库的行
    • 字段：类似关系型数据库的列
  • 操作：
    • insert：新增，若新增数据的主键已经存在，则会抛异常提示主键重复，不保存当前数据。
    • save：新增或更新，若新增数据的主键已经存在，则会对当前已经存在的数据进行修改操作。
    • find：查询
    • count：计数
    • update：更新
    • remove：删除文档
    • drop：删除集合

// db.collectionName.insert(document)
db.users.insert({
username: "smith"
})
db.users.save({
username: "jones"
})// db.collectionName.find(query)
db.users.find()
db.users.find({username:"smith"})
db.users.find({
$and:[
{username:"smith"},
{_id:ObjectId("5bac8a98f47a87df04000912")}
]
})db.users.count()// 更新操作
db.users.update({country:"China"},{$set:{username:"smith"}})// 替换操作
db.users.update({username:"smith"},{country:"China"})// 删除字段
db.users.update({username:"smith"},{$unset:{country:1}})// 修改操作
db.users.update({
username: "smith"
}, {
$set: {
favorites: {
cities: ["China", "Japan"],
movies: ["1408", "The String", "Casablanca"]
}
}
})// 添加到容器中
db.users.update({
"favorites.movies": "Casablanca"
}, {
//$push：不保证唯一
$addToSet: {"favorites.movies":"Te Room"}
},
false, // 当文档不存在时，是否插入
true // 是否进行多个更新
)// 删除文档
db.users.remove()// 删除集合
db.users.drop()

2 索引

// 批量插入
for(var i = 0;i<20000;i++){
db.numbers.save({num:i});
}// 范围查询
db.numbers.find({num:{$gte:50,$lt:70}});db.numbers.find({num:{$gt:50}}).explain("executionStats");
// 无索引结果：
{
"queryPlanner": {
"plannerVersion": NumberInt("1"), // 版本
"namespace": "naladb.numbers", // 库.集合
"indexFilterSet": false, // 是否有indexFilterSet
"parsedQuery": {
"num": {
"$gt": 50
}
},
"winningPlan": { //查询优化器针对该query所返回的最优执行计划的详细内容
"stage": "COLLSCAN", // 最优执行计划的stage
"filter": { // 过滤条件
"num": {
"$gt": 50
}
},
"direction": "forward" // 查询顺序
},
"rejectedPlans": [ ] // 其他执行计划
},
"executionStats": {
"executionSuccess": true, // 执行结果
"nReturned": NumberInt("87"), //
"executionTimeMillis": NumberInt("0"), // 执行时间
"totalKeysExamined": NumberInt("0"), // 索引扫描条目
"totalDocsExamined": NumberInt("138"), // 文档扫描条目
"executionStages": {
"stage": "COLLSCAN",
"filter": {
"num": {
"$gt": 50
}
},
"nReturned": NumberInt("87"), // 返回的条目
"executionTimeMillisEstimate": NumberInt("0"),
"works": NumberInt("140"),
"advanced": NumberInt("87"),
"needTime": NumberInt("52"),
"needYield": NumberInt("0"),
"saveState": NumberInt("1"),
"restoreState": NumberInt("1"),
"isEOF": NumberInt("1"),
"invalidates": NumberInt("0"),
"direction": "forward",
"docsExamined": NumberInt("138")
}
},
"serverInfo": {
"host": "i-t0gpyby1",
"port": NumberInt("27017"),
"version": "3.4.5",
"gitVersion": "520b8f3092c48d934f0cd78ab5f40fe594f96863"
},
"ok": 1
}
// 有索引结果
{
"queryPlanner": {
"plannerVersion": NumberInt("1"),
"namespace": "naladb.numbers",
"indexFilterSet": false,
"parsedQuery": {
"$and": [
{
"num": {
"$lt": 70
}
},
{
"num": {
"$gt": 50
}
}
]
},
"winningPlan": {
"stage": "FETCH",
"inputStage": {
"stage": "IXSCAN",
"keyPattern": {
"num": 1
},
"indexName": "num_1",
"isMultiKey": false,
"multiKeyPaths": {
"num": [ ]
},
"isUnique": false,
"isSparse": false,
"isPartial": false,
"indexVersion": NumberInt("2"),
"direction": "forward",
"indexBounds": {
"num": [
"(50.0, 70.0)"
]
}
}
},
"rejectedPlans": [ ]
},
"executionStats": {
"executionSuccess": true,
"nReturned": NumberInt("19"),
"executionTimeMillis": NumberInt("2"),
"totalKeysExamined": NumberInt("19"), // 通过索引扫描的个数
"totalDocsExamined": NumberInt("19"),
"executionStages": {
"stage": "FETCH",
"nReturned": NumberInt("19"),
"executionTimeMillisEstimate": NumberInt("0"),
"works": NumberInt("20"),
"advanced": NumberInt("19"),
"needTime": NumberInt("0"),
"needYield": NumberInt("0"),
"saveState": NumberInt("0"),
"restoreState": NumberInt("0"),
"isEOF": NumberInt("1"),
"invalidates": NumberInt("0"),
"docsExamined": NumberInt("19"),
"alreadyHasObj": NumberInt("0"),
"inputStage": {
"stage": "IXSCAN",
"nReturned": NumberInt("19"),
"executionTimeMillisEstimate": NumberInt("0"),
"works": NumberInt("20"),
"advanced": NumberInt("19"),
"needTime": NumberInt("0"),
"needYield": NumberInt("0"),
"saveState": NumberInt("0"),
"restoreState": NumberInt("0"),
"isEOF": NumberInt("1"),
"invalidates": NumberInt("0"),
"keyPattern": {
"num": 1
},
"indexName": "num_1", // 使用的索引名
"isMultiKey": false,
"multiKeyPaths": {
"num": [ ]
},
"isUnique": false,
"isSparse": false,
"isPartial": false,
"indexVersion": NumberInt("2"),
"direction": "forward",
"indexBounds": {
"num": [
"(50.0, 70.0)"
]
},
"keysExamined": NumberInt("19"),
"seeks": NumberInt("1"),
"dupsTested": NumberInt("0"),
"dupsDropped": NumberInt("0"),
"seenInvalidated": NumberInt("0")
}
}
},
"serverInfo": {
"host": "i-t0gpyby1",
"port": NumberInt("27017"),
"version": "3.4.5",
"gitVersion": "520b8f3092c48d934f0cd78ab5f40fe594f96863"
},
"ok": 1
}
// 参考：https://www.cnblogs.com/c-abc/p/6023824.html// 创建索引
db.numbers.createIndex({num:1})
// 查看索引
db.numbers.getIndexes()

状态描述
COLLSCAN全表扫描
IXSCAN索引扫描
FETCH根据索引去检索指定document
SHARD_MERGE将各个分片返回数据进行merge
SORT表明在内存中进行了排序
LIMIT使用limit限制返回数
SKIP使用skip进行跳过
IDHACK针对_id进行查询
SHARDING_FILTER通过mongos对分片数据进行查询
COUNT利用db.coll.explain().count()之类进行count运算
COUNTSCANcount不使用Index进行count时的stage返回
COUNT_SCANcount使用了Index进行count时的stage返回
SUBPLA未使用到索引的$or查询的stage返回
TEXT使用全文索引进行查询时候的stage返回
PROJECTION限定返回字段时候stage的返回

3 基本管理

// 数据库
show dbs;// 集合
show collections;// 数据库信息
db.stats()
db.runCommand({dbstats:1});
// 结果
{
"db": "test",
"collections": NumberInt("4"), // 集合数
"views": NumberInt("0"),
"objects": NumberInt("471233"), // 记录数
"avgObjSize": 179.008626305883, // 每条记录的平均大小
"dataSize": 84354772, // 记录的总大小
"storageSize": 30236672, // 预分配的存储空间大小
"numExtents": NumberInt("0"), // 事件数
"indexes": NumberInt("9"), //索引数
"indexSize": 10051584, // 索引大小
"ok": 1
}// 集合信息
db.collectionName.stats()
db.runCommand({collstats:"numbers"})
// 结果
{
"ns": "naladb.numbers",
"size": NumberInt("700000"), // 大小
"count": NumberInt("20000"), // 总记录数
"avgObjSize": NumberInt("35"),
"storageSize": NumberInt("376832"),
"capped": false,
// 参考：https://yq.aliyun.com/articles/255163
"wiredTiger": {
...
},
"nindexes": NumberInt("2"),
"totalIndexSize": NumberInt("454656"),
"indexSizes": {
"_id_": NumberInt("221184"), // 索引_id的大小
"num_1": NumberInt("233472")
},
"ok": 1
}

  • 查看mongo shell指令实现

db.runCommand
// 结果
// v3.4.5
function (command) {
if (!isString(command) && !isObject(command))
nav_throwError("command must be string or object");
return this.forwardToCustomFunction("databaseRunCommand", command);
}// v2.6.10
function ( obj ){
if ( typeof( obj ) == "string" ){
var n = {};
n[obj] = 1;
obj = n;
}
return this.getCollection( "$cmd" ).findOne( obj );
}db.collectionName.save
// 结果
function (document, options) {
if (!document)
nav_throwError("db.collection.save requires document object"); if (isNumber(document) || isString(document))
nav_throwError("db.collection.save only accept document object"); if (isUndefined(document._id)) {
document._id = new ObjectId();
return this.insert(document, options);
} else {
options = options || {};
options.upsert = true;
return this.update({ _id: document._id }, document, options);
}
}