# _Id 不能直接和 String 进行比较
user._id === article.userId
在 mongoose 中不能使用上面的比较，因为 monoose 中的 _id 是ObjectID 类型，是 BSON 中的一种类型，所以不能直接比较，如果需要比较，则可以用 ObjectId 中的 equals 方法
user._id.equals(article.userId)
# toObject toJson
在mongoose 中查询出来的对象默认是不可更改的，如果需要更改，则需要在对象后添加 toObject 才能更改
let model = new Model();
model.name = "model name";
console.info(model.name); // null
model = model.toObject();
model.name = 'model name';
console.info(model.name); // model.name
# lean
上方的两个问题 _id 比较， 和 toObject 出现的根本原因是通过mongooses 查询出来的对象还不能算是一个JavaScript 还是一个 Mongoose 的对象，查询出来的对象是可以进行 update, create, delete 等一系列的操作的。
这个时候我们可以用 查询的 lean 方法，手动的将查询出来的 mongoose 对象转换为 JavaScript 对象 这个时候就不会有上面的问题了
this.ctx.model.user.find().lean();
# 字段递增、递减
递增
await model.findOneAndUpdate({ _id }, { $inc: {views: 1} });
递减，需要判断当前已经大于 0
await model.findOneAndUpdate({ _id, {views: {$gt: 0}}, { $inc: {views: -1} }});
# 常用查询
| 方法名 | 含义 | |
|---|---|---|
| find | 通用查询，方法的查询结果是数组，即使没查询到内容，也会返回 [] 空数组。 | |
| findById | Model.findById(id,[projection],[options],[callback]) | |
| findOne | Model.findOne(conditions, [projection], [options], [callback]) | 该方法返回查找到的所有实例的第一个 |
操作符
| $eq | 与指定的值相等 |
|---|---|
| $ne | 与指定的值不相等 |
| $gt | 大于指定的值 |
| $gte | 大于等于指定的值 |
| $lt | 小于指定的值 |
| $lte | 小于等于指定的值 |
| $in | 与查询数组中指定的值中的任何一个匹配 |
| $nin | 与查询数组中指定的值中的任何一个都不匹配 |
字段相关操作符
| 符号 | 描述 |
|---|---|
| $exists | 匹配存在制定字段的文档 |
| $type | 返回字段属于指定类型的文档 |
数组字段查找
| 符号 | 描述 |
|---|---|
| $all | 匹配包含查询数组中指定的所有条件的数组字段 |
| $elemMatch | 匹配数组字段中的某个值满足 $elemMatch 中指定的所有条件 |
| $size | 匹配数组字段的 length 与指定的大小一样的 document |
projection 投影
其实就是看哪个字段显示，哪个字段不显示
UserModel.find({}, {name: 1, age: 1, sex: 0});
上面的查询就代表了，只显示 name、age、sex 字段
Options
| 操作 | 作用 |
|---|---|
| sort | 按照排序规则根据所给的字段进行排序，值可以是 asc，desc，ascending，descending，1，和 -1。 |
| limit | 指定返回结果的最大数量 |
| skip | 指定要跳过的文档数量 |
| lean | 返回普通的 js 对象，而不是 Mongoose Documents。建议不需要 mongoose 特殊处理就返给前端的数据都最好使用该方法转成普通 js 对象。 |
TIP
在 limit、skip 一起使用时，调用顺序并不重要，返回的数据都是先排序后限制数量
// 效果一样
Model.find().limit(2).sort('age');
Model.find().sort('age').limit(2);
# 修改
- findOneAndUpdate
- findByIdAndUpdate
- update
- updateMany
Model.findOneAndUpdate(filter, update, [options], [callback]);
// update
// {operator: { field: value, ... }}
WARNING
必须使用 update 操作符。如果没有操作符或操作符不是 update 操作符，统一被视为 $set 操作（mongoose 特有）
字段相关操作符
| 符号 | 描述 |
|---|---|
| $set | 设置字段值 |
| $currentDate | 设置字段值为当前时间，可以是 Date 或时间戳格式。 |
| $min | 只有当指定值小于当前字段值时更新 |
| $max | 只有当指定值大于当前字段值时更新 |
| $inc | 将字段值增加指定数量，指定数量可以是负数，代表减少。 |
| $mul | 将字段值乘以指定数量 |
| $unset | 删除指定字段，数组中的值删后改为 null。 |
数组字段相关操作符
| 符号 | 描述 |
|---|---|
| $ | 充当占位符，用来表示匹配查询条件的数组字段中的第一个元素 {operator:{ "arrayField.$" : value }} |
| $addToSet | 向数组字段中添加之前不存在的元素 { $addToSet: {arrayField: value, ... }}，value 是数组时可与 $each 组合使用。 |
| $pop | 向数组字段的末尾添加元素 { $push: { arrayField: value, ... } }，value 是数组时可与 $each 等修饰符组合使用 |
| $pull | 移除数组字段中的第一个或最后一个元素 { $pop: {arrayField: -1(first) / 1(last), ... } } |
| $pullAll | 移除数组字段中与查询条件匹配的所有元素 { $pull: {arrayField: value / condition, ... } } |
| $push | 从数组中删除所有匹配的值 { $pullAll: { arrayField: [value1, value2 ... ], ... } } |
修饰符
- $each
- $position
- $slice
- $sort
# 删除
- findOneAndDelete
- findByIdAndDelete
- deleteMany
- deleteOne
- findOneAndRemove
- findByIdAndRemove
- remove
# aggregate
$project
修改文档的结构，可以用来重命名、增加或删除文档中字段
//只返回a和b字段 Model.aggregate([ { $project: { a: 1, b: 1 } } ]);$match
用于过滤文档，用法类似于find()方法中的参数
//返回符合price大于或等于100的数据 Model.aggregate([ { $match: { 'price': { $gte: 100 } } } ]);$limit
只返回一条数据
Model.aggregate([ { $limit: 1 } ]);$skip
跳过第一条，返回之后的数据
Model.aggregate([ { $skip: 1 } ]);$sort
以price倒序排列
Model.aggregate([ { $sort: { 'price': -1 } } ]);$group
以order_id进行分组，并统计每组的数量
Model.aggregate([ { $group: {_id: "$order_id", total: {$sum: "$num"}} } ]);$lookup
Model.aggregate([ { $lookup: { from: 'student', // 和student表进行关联 localField: 'class_id', // 此表字段名为 class_id foreignField: 'class_id', // 关联表中字段为 class_id as: 'students' // 用students 字段接收符合要求的内容 } }, ]);
# MongoDB 导入导出
导出
mongodump --archive=egg_xgimi_app.gz --gzip --db=egg_xgimi_app
导入
mongorestore -h 127.0.0.1 -d 导入的数据库库名称
mongorestore --gzip --archive=<filename>.agz --db test -u <username> -p <password> --authenticationDatabase 'admin' --port 27000 --host <hostname>
# Model Virtual
TIP
mongoose 的 virtual 需要配合 populate 使用，有奇效
Task.virtual('comment', {
ref: 'Comment',
localField: '_id',
foreignField: 'task',
justOne: false,
count: true,
});
# 固定集合 capped
在某些特定场景下，我们需要限制数据集和的大小，当它超过固定大小的时候就删除。这个时候就需要 MongoDB 里面的固定集合了
const SysLog = new Schema({
type: String
}, { timestamps: true, versionKey: false, strict: false, capped: { size: 1024 * 1024 * 10, max: 10000 } });
- size 配置当前数据集的最大大小 【单位 byte】
- max 当前数据集的最大条数，两个满足一个就会覆盖
通过 db.model.stats() 可以查看当前文档是否是固定集合，和当前集合所使用的条数
文档详情 db.model.stats()
{
"ns" : "",
"size" : 10484818.0,
"count" : 6860.0,
"avgObjSize" : 1528.0,
"storageSize" : 1060864.0,
"capped" : true,
"max" : 10000.0,
"maxSize" : 10485760.0,
"sleepCount" : 0.0,
"sleepMS" : 0.0,
"wiredTiger" : {
"metadata" : {
"formatVersion" : 1.0
},
"creationString" : "access_pattern_hint=none,allocation_size=4KB,app_metadata=(formatVersion=1),assert=(commit_timestamp=none,durable_timestamp=none,read_timestamp=none),block_allocation=best,block_compressor=snappy,cache_resident=false,checksum=on,colgroups=,collator=,columns=,dictionary=0,encryption=(keyid=,name=),exclusive=false,extractor=,format=btree,huffman_key=,huffman_value=,ignore_in_memory_cache_size=false,immutable=false,internal_item_max=0,internal_key_max=0,internal_key_truncate=true,internal_page_max=4KB,key_format=q,key_gap=10,leaf_item_max=0,leaf_key_max=0,leaf_page_max=32KB,leaf_value_max=64MB,log=(enabled=true),lsm=(auto_throttle=true,bloom=true,bloom_bit_count=16,bloom_config=,bloom_hash_count=8,bloom_oldest=false,chunk_count_limit=0,chunk_max=5GB,chunk_size=10MB,merge_custom=(prefix=,start_generation=0,suffix=),merge_max=15,merge_min=0),memory_page_image_max=0,memory_page_max=10m,os_cache_dirty_max=0,os_cache_max=0,prefix_compression=false,prefix_compression_min=4,source=,split_deepen_min_child=0,split_deepen_per_child=0,split_pct=90,type=file,value_format=u",
"type" : "file",
"uri" : "statistics:table:collection-125--2403229025471591555",
"LSM" : {
"bloom filter false positives" : 0.0,
"bloom filter hits" : 0.0,
"bloom filter misses" : 0.0,
"bloom filter pages evicted from cache" : 0.0,
"bloom filter pages read into cache" : 0.0,
"bloom filters in the LSM tree" : 0.0,
"chunks in the LSM tree" : 0.0,
"highest merge generation in the LSM tree" : 0.0,
"queries that could have benefited from a Bloom filter that did not exist" : 0.0,
"sleep for LSM checkpoint throttle" : 0.0,
"sleep for LSM merge throttle" : 0.0,
"total size of bloom filters" : 0.0
},
"block-manager" : {
"allocations requiring file extension" : 135.0,
"blocks allocated" : 613.0,
"blocks freed" : 469.0,
"checkpoint size" : 741376.0,
"file allocation unit size" : 4096.0,
"file bytes available for reuse" : 303104.0,
"file magic number" : 120897.0,
"file major version number" : 1.0,
"file size in bytes" : 1060864.0,
"minor version number" : 0.0
},
"btree" : {
"btree checkpoint generation" : 289.0,
"column-store fixed-size leaf pages" : 0.0,
"column-store internal pages" : 0.0,
"column-store variable-size RLE encoded values" : 0.0,
"column-store variable-size deleted values" : 0.0,
"column-store variable-size leaf pages" : 0.0,
"fixed-record size" : 0.0,
"maximum internal page key size" : 368.0,
"maximum internal page size" : 4096.0,
"maximum leaf page key size" : 2867.0,
"maximum leaf page size" : 32768.0,
"maximum leaf page value size" : 67108864.0,
"maximum tree depth" : 3.0,
"number of key/value pairs" : 0.0,
"overflow pages" : 0.0,
"pages rewritten by compaction" : 0.0,
"row-store empty values" : 0.0,
"row-store internal pages" : 0.0,
"row-store leaf pages" : 0.0
},
"cache" : {
"bytes currently in the cache" : 12365742.0,
"bytes dirty in the cache cumulative" : 114582203.0,
"bytes read into cache" : 0.0,
"bytes written from cache" : 64606581.0,
"checkpoint blocked page eviction" : 0.0,
"data source pages selected for eviction unable to be evicted" : 0.0,
"eviction walk passes of a file" : 0.0,
"eviction walk target pages histogram - 0-9" : 0.0,
"eviction walk target pages histogram - 10-31" : 0.0,
"eviction walk target pages histogram - 128 and higher" : 0.0,
"eviction walk target pages histogram - 32-63" : 0.0,
"eviction walk target pages histogram - 64-128" : 0.0,
"eviction walks abandoned" : 0.0,
"eviction walks gave up because they restarted their walk twice" : 0.0,
"eviction walks gave up because they saw too many pages and found no candidates" : 0.0,
"eviction walks gave up because they saw too many pages and found too few candidates" : 0.0,
"eviction walks reached end of tree" : 0.0,
"eviction walks started from root of tree" : 0.0,
"eviction walks started from saved location in tree" : 0.0,
"hazard pointer blocked page eviction" : 0.0,
"in-memory page passed criteria to be split" : 4.0,
"in-memory page splits" : 2.0,
"internal pages evicted" : 0.0,
"internal pages split during eviction" : 0.0,
"leaf pages split during eviction" : 0.0,
"modified pages evicted" : 0.0,
"overflow pages read into cache" : 0.0,
"page split during eviction deepened the tree" : 0.0,
"page written requiring cache overflow records" : 0.0,
"pages read into cache" : 0.0,
"pages read into cache after truncate" : 1.0,
"pages read into cache after truncate in prepare state" : 0.0,
"pages read into cache requiring cache overflow entries" : 0.0,
"pages requested from the cache" : 10404.0,
"pages seen by eviction walk" : 0.0,
"pages written from cache" : 577.0,
"pages written requiring in-memory restoration" : 0.0,
"tracked dirty bytes in the cache" : 0.0,
"unmodified pages evicted" : 0.0
},
"cache_walk" : {
"Average difference between current eviction generation when the page was last considered" : 0.0,
"Average on-disk page image size seen" : 0.0,
"Average time in cache for pages that have been visited by the eviction server" : 0.0,
"Average time in cache for pages that have not been visited by the eviction server" : 0.0,
"Clean pages currently in cache" : 0.0,
"Current eviction generation" : 0.0,
"Dirty pages currently in cache" : 0.0,
"Entries in the root page" : 0.0,
"Internal pages currently in cache" : 0.0,
"Leaf pages currently in cache" : 0.0,
"Maximum difference between current eviction generation when the page was last considered" : 0.0,
"Maximum page size seen" : 0.0,
"Minimum on-disk page image size seen" : 0.0,
"Number of pages never visited by eviction server" : 0.0,
"On-disk page image sizes smaller than a single allocation unit" : 0.0,
"Pages created in memory and never written" : 0.0,
"Pages currently queued for eviction" : 0.0,
"Pages that could not be queued for eviction" : 0.0,
"Refs skipped during cache traversal" : 0.0,
"Size of the root page" : 0.0,
"Total number of pages currently in cache" : 0.0
},
"compression" : {
"compressed page maximum internal page size prior to compression" : 4096.0,
"compressed page maximum leaf page size prior to compression " : 131072.0,
"compressed pages read" : 0.0,
"compressed pages written" : 559.0,
"page written failed to compress" : 0.0,
"page written was too small to compress" : 18.0
},
"cursor" : {
"bulk loaded cursor insert calls" : 0.0,
"cache cursors reuse count" : 7495.0,
"close calls that result in cache" : 0.0,
"create calls" : 5.0,
"insert calls" : 7154.0,
"insert key and value bytes" : 10950567.0,
"modify" : 0.0,
"modify key and value bytes affected" : 0.0,
"modify value bytes modified" : 0.0,
"next calls" : 362137.0,
"open cursor count" : 0.0,
"operation restarted" : 0.0,
"prev calls" : 293.0,
"remove calls" : 294.0,
"remove key bytes removed" : 525.0,
"reserve calls" : 0.0,
"reset calls" : 18398.0,
"search calls" : 291.0,
"search near calls" : 3088.0,
"truncate calls" : 0.0,
"update calls" : 0.0,
"update key and value bytes" : 0.0,
"update value size change" : 0.0
},
"reconciliation" : {
"dictionary matches" : 0.0,
"fast-path pages deleted" : 0.0,
"internal page key bytes discarded using suffix compression" : 1806.0,
"internal page multi-block writes" : 0.0,
"internal-page overflow keys" : 0.0,
"leaf page key bytes discarded using prefix compression" : 0.0,
"leaf page multi-block writes" : 34.0,
"leaf-page overflow keys" : 0.0,
"maximum blocks required for a page" : 1.0,
"overflow values written" : 0.0,
"page checksum matches" : 364.0,
"page reconciliation calls" : 52.0,
"page reconciliation calls for eviction" : 0.0,
"pages deleted" : 0.0
},
"session" : {
"object compaction" : 0.0
},
"transaction" : {
"update conflicts" : 0.0
}
},
"nindexes" : 1.0,
"indexBuilds" : [
],
"totalIndexSize" : 151552.0,
"indexSizes" : {
"_id_" : 151552.0
},
"scaleFactor" : 1.0,
"ok" : 1.0
}
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