nosql

MongoDB: How to represent a schema diagram in a thesis?

由 允我心安 提交于 2019-12-31 08:14:24
问题 I am currently writing a thesis and need to display the schema of my MongoDB in a diagram. I have found no resources about diagrams for document-based databases. There are Entity Relationship Diagrams (ERD) for relational databases. What options do I have for MongoDB? I've noticed that a lot of blogs just display the raw JSON as their "diagram" but this isn't feasible in my thesis. Here is a sample of one of my JSON structures: //MultiChoiceQuestion { "title": "How are you?", "valid_answers"

How does Voldemort compare to Cassandra?

由 风流意气都作罢 提交于 2019-12-31 08:04:17
问题 How does Voldemort compare to Cassandra? I'm not talking about size of community and only want to hear from people who have actually used both. Especially I'm interested in: How they dynamically scale when adding and removing nodes Query performance How they scale when adding nodes (linear)? Write speed 回答1: Voldemort's support for adding nodes was just added recently (this month). So I would expect Cassandra's to be more robust given the longer time to cook and a larger community testing.

Explain Merkle Trees for use in Eventual Consistency

由 别说谁变了你拦得住时间么 提交于 2019-12-31 07:53:05
问题 Merkle Trees are used as an anti-entropy mechanism in several distributed, replicated key/value stores: Dynamo Riak Cassandra No doubt an anti-entropy mechanism is A Good Thing - transient failures just happen, in production. I'm just not sure I understand why Merkle Trees are the popular approach. Sending a complete Merkle tree to a peer involves sending the local key-space to that peer, along with hashes of each key value, stored in the lowest levels of the tree. Diffing a Merkle tree sent

How can I make Parse.Query.AND?

由 倖福魔咒の 提交于 2019-12-31 01:45:08
问题 I need to connect 2 queries in Parse.com with an and, my code is: var queryDeseo1 = new Parse.Query(DeseosModel); queryDeseo1.equalTo("User", Parse.User.current()); queryDeseo1.equalTo("Deseo", artist); queryDeseo1.find({... The result of the .find is all the objects with User = Parse.User.current()) and all the objects with Deseo = artist but I want the objects with the two queries together: User = Parse.User.current()) and Deseo = artist 回答1: You've actually got it setup correctly to do an

Redis安装和使用总结

由 妖精的绣舞 提交于 2019-12-30 22:56:41
文章目录 一、Redis概述 1. 基本概念 2. Redis的优点 二、Redis安装 三、Redis使用 1.1 shell基本操作 清空数据库 删除给定的一个或多个key 检查给定key 是否存在 查找所有符合给定模式pattern 的key 当前数据库的key 移动到给定的数据库DB 将key 改名为newkey 返回key所储存的值的类型 1.2 五种数据类型shell操作 a. String类型的操作——key：value b. Redis的List类型操作 c. Redis的SET类型操作 d. Redis的ZSET类型的操作 e. Redis的HASH类型的操作 2. Java API 依赖 创建客户端 使用案例 一、Redis概述 1. 基本概念 redis是一个key-value存储系统。和Memcached类似，它支持存储的value类型相对更多，包括string(字符串)、list(链表)、set(集合)、zset(sorted set --有序集合)和hash（哈希类型）。 2. Redis的优点 1、数据模型比较简单； redis 2、需要灵活性更强的IT系统；nosql 效率高 3、对数据库性能要求较高； nosql 4、不需要高度的数据一致性；nosql 数据一致性支持弱，弱化事务 二、Redis安装 安装gcc yum install - y

MongoDB $and operator query in PHP

由 谁都会走 提交于 2019-12-30 16:37:13
问题 I've been having difficulty with the $and operator and MongoRegex. I'm doing a regex record search for "Amazon" that also has the field "enabled" set to 1. This is my query. $search = "Amazon"; $results = $collection->find(array( '$and' => array( array('orgname' => new MongoRegex("/.*$search.*/")), array('enabled' => '1') ) )); Maybe someone can point out what I'm doing wrong. Thanks in Advance. 回答1: I think that in this case you don't need to use the $and operator. Try this: $search =

Are There Bidirectional Relational Databases?

由 |▌冷眼眸甩不掉的悲伤 提交于 2019-12-30 16:18:02
问题 I'd like to create a clothing database, where items from tables such as 'tops' or 'bottoms' (pants, skirts) can be matched with each other and with items in other tables such as hats or shoes. I want to be able to relate all tables to each other in both directions (each skirt goes with many tops, and each top goes with many pants, etc) and I want each table to be related to each other. E.g, I want to query 'what items look good with these pants' and see a list of shirts, shoes, etc. Using a

Cassandra Optimistic Locking

由 ↘锁芯ラ 提交于 2019-12-30 08:55:47
问题 I have a cassandra table1: CREATE TABLE Policy.table1 ( name VARCHAR , date TIMESTAMP , version_num INT, PRIMARY KEY ( name )) WITH caching = 'all' -- and memtable_flush_period_in_ms = 7200 ; ; I need to implement optimistic locking on tis table. When we read a row from table1 we remember its version_num. And when we want to update this row we compare current version_num value and value that we remembered. Also we need to increment version_num on each update. Problems: We cannot put version

Cassandra Optimistic Locking

由 若如初见. 提交于 2019-12-30 08:55:12
问题 I have a cassandra table1: CREATE TABLE Policy.table1 ( name VARCHAR , date TIMESTAMP , version_num INT, PRIMARY KEY ( name )) WITH caching = 'all' -- and memtable_flush_period_in_ms = 7200 ; ; I need to implement optimistic locking on tis table. When we read a row from table1 we remember its version_num. And when we want to update this row we compare current version_num value and value that we remembered. Also we need to increment version_num on each update. Problems: We cannot put version

Updating part of a Document in Azure DocumentDB

由 让人想犯罪 __ 提交于 2019-12-30 08:04:28
问题 Is there a way to update part of a document in a DocumentDB collection? I know that ReplaceDocumentAsync lets you update a document, but you have to replace the entire document. This sounds kind of scary. If I have an object that has other objects nested I will have to query for the parent document and then replace the entire document to update a nested part of the object. Does DocumentDB handle ReplaceDocumentAsync in a way that makes it perform better than it might seem on the surface? 回答1:
订阅 nosql