nosql

How to come up with students and teacher relation in Firebase?

由 送分小仙女□ 提交于 2020-01-07 04:58:27
问题 I am trying to create just basic data structure for students -> teacher relation. Students -> Teacher (many to many) Each students can have many teachers Users uid1: type: student name: Alex Smith teachers: [uid5: true, uid4: true ] //is it better to do it like this? uid2: type: student name: Michael A teachers: [ uid5: true] uid3: type: student name: Michael A teachers: [uid5: true] uid4: type: teacher name: Alex Smith teacher: [uid3: true] //is it better to use their uid? uid5: type:

Async Bulk(batch) insert to MySQL(or MongoDB?) via Node.js

由 为君一笑 提交于 2020-01-07 02:25:30
问题 Straight to the Qeustion ->. The problem : To do async bulk inserts (not necessary bulk, if MySql can Handle it) using Node.js (coming form a .NET and PHP background) Example : Assume i have 40(adjustable) functions doing some work(async) and each adding a record in the Table after its single iteration, now it is very probable that at the same time more than one function makes an insertion call. Can MySql handle it that ways directly?, considering there is going to be an Auto-update field. In

现时代DBA存在的价值

由 被刻印的时光 ゝ 提交于 2020-01-07 00:39:28
【推荐】2019 Java 开发者跳槽指南.pdf(吐血整理) >>> 简介： 未来DBA的存在数量是否会越来越少，或者严重一点，DBA这个职业直接消 原创： 走起君 SQLServer走起 最近走起君在思考一个问题，未来DBA的存在数量是否会越来越少，或者严重一点，DBA这个职业直接消失，现在是2019年，很快踏入2020年，数据库行业还在飞速发展 下面是走起君思考后，做出的一些看法： 既然DBA是管理数据库的人，那么这个问题是否可以理解为，现在市面上的数据库是否有被DBA管理的必要 下面走起君大概做了四个数据库/数据管理的分类 第一个商业数据库 现在商业数据库基本上用的最多的就是：Oracle、SQL Server、DB2 这三家数据库厂商都在它们的最新版本数据库产品里分别加入了：区块链、nosql、图数据库、AI人工智能、机器学习、数据库自治等功能 从中可以看出几个趋势 第一个趋势是，对于传统的oltp数据库功能，这些商业数据库都已经趋向于使用人工智能/机器学习等技术去自动优化数据库，尽量减少人工的介入 第二个趋势是，商业数据库不断向外延伸，增加了nosql、图数据库、内存表等功能，变得越来越庞大，以满足企业越来越多的需求，通吃nosql数据库和图数据库的市场 第三个趋势是，跟大数据相关技术打通 而走起君对于商业数据库DBA的看法是，未来商业数据库DBA会越来越少

Need to querying into a column (or collection) in Cassandra

由 僤鯓⒐⒋嵵緔 提交于 2020-01-06 20:19:45
问题 everyone :D I'm working with Cassandra (Datastax version) and I have an issue. I want to modeling a column who (always) gonna change. That's very hard, because I can't just create a column family with 1,2,3,4..10 columns. Because, tomorrow probably can change. I think in collections, but I got to query into these. I mean, I need query into this information every second. Ex: With map: <'col1':'val1','col2':'val2'> I need to query like this: SELECT * FROM example WHERE 'col1' = 'val1' AND 'col2

Find records from 7 days ago from now in MongoDB

由 左心房为你撑大大i 提交于 2020-01-06 20:19:15
问题 I've a collection containing objects represented like the one below: /* 1 */ { "_id" : ObjectId("551c6605e4c6ac495c923aab"), "sender_id" : ObjectId("551c6605e4c6ac495c923aac"), "rep_sender_id" : "38", "sender_name" : "Melissa Aldridge", "sender_title" : null, "sender_photo_id" : "https://url/web/bundles/pdone/media/representative/photo/qlv_aldridge_melissa.jpg", "sender_company" : "", "recipient_id" : ObjectId("5356af6ae4c6acdc10450a23"), "recipient_name" : "MAX GUCILATAR", "recipient_title"

Returning custom fields in MongoDB

由 梦想的初衷 提交于 2020-01-06 19:54:27
问题 I have a mongoDB collection with an array field that represents the lists the user is member of. user { screen_name: string listed_in: ['list1', 'list2', 'list3', ...] //Could be more than 10000 elements (I'm aware of the BSON 16MB limits) } I am using the *listed_in* field to get the members list db.user.find({'listed_in': 'list2'}); I also need to query for a specific user and know if he is member of certain lists var user1 = db.findOne({'screen_name': 'user1'}); In this case I will get the

Lack of rich querying functionality in NoSQL?

由 不想你离开。 提交于 2020-01-06 15:43:07
问题 Every time i contemplate using NoSQL for a solution i always get hung up on the lack of rich querying functionality. I think it very well be my lack of understanding of NoSQL. It also might be due to the fact of i'm comfortable very comfortable with SQL. From my understanding NoSQL really lends itself well for simple schema scenarios (so its probably not going to work well for a relational database where you have 50+ tables). Even for trivial scenarios i always seem to want rich query

redis笔记之一

由 让人想犯罪 __ 提交于 2020-01-06 15:32:49
NoSQL简介 全称是Not Only SQL,泛指菲关系型数据库，它是通过键值对存储数据并且将数据存储在内存中。而像mysql，sql server这些通过关系表存数据的就叫关系型数据库 为什么需要NoSQL 主要传统的关系型数据库暴露了许多问题 1.对数据库高并发读写的需求 高并发就是同一时间有许多用户访问同一网站造成访问量太大容易造成服务器崩溃，而传统的解决方法就是搭建集群，通俗的讲就是原先一个服务器提供服务，现在变成多个服务器提供服务 2.高负载-对海量数据的高效率存储和访问的需求 通俗的讲就是数据量非常大，造成没地方存储或者访问查询sql的语句超过上千万造成查询非常低下 3.高扩展-对数据库的高可扩展性和高可用性的需求 通俗的讲相当于银行窗口排队，刚开始一个窗口不能满足需求，后来增加多个窗口，而增加窗口不会造成业务上的不同，也就是集群起来很方便 主流的NoSQL产品 主要有四大类 1.键值（key-value）存储数据库 主流产品：redis 典型应用：内容缓存，主要用于处理大量数据的高访问负载 优势：快速查询 劣势：存储的数据缺少结构化 2.列存储数据库 主流产品：HBase 典型应用：分布式的文件系统 优势：查询速度快，可扩展性强，更容易进行分布式扩展 劣势：功能相对局限 3.文档数据库 主流产品：MongoDB 典型应用：web应用 优势：数据结构要求不严格 劣势

CouchDB update handlers: document id must not be empty

由 孤街醉人 提交于 2020-01-06 13:14:25
问题 I wrote simple update handler: { "handler": "function (doc, req) { if (req.userCtx.roles.indexOf('editor') < 0) return [req.userCtx, 'access error']; if (!doc) { return [doc, 'nothing']; } doc.date = new Date(); doc.edited_by = req.userCtx.name; return [doc, toJSON(doc)]; }" } When I'm trying to query from Mozilla HttpRequester http://192.168.0.34:5984/records/_design/records/_update/handler , i'm getting with that's data {"title":"testtest","content":"test"} And getting {"error":"bad_request

Why two remove reference item are there for Model.remove in Mongoose API docs?

由 ▼魔方 西西 提交于 2020-01-06 07:56:15
问题 After landing into the API docs of mongoose, there is left side menu, Under model.js section. We see something like this: - model.js -Model -save -increment -remove <== 1 -model -$where -ensureIndexes -remove <== 2 ... Both remove are having the link to Model#remove([fn]) There is one more topic which is not linked. Titled Model.remove(conditions, [callback]) which is documented under the same model.js section. (just after the topic Model.ensureIndexes) Could anyone one tell me what is the
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