key-value | 易学教程

Key-Value Database

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问题 I need to store short strings (50+ characters), and quickly look them up. At first I wanted to use SQLite for this. I created a single table with a single indexed TEXT column. Using all kinds of low-level tricks I could fill the database with 1 million strings in 10 seconds. The problem was that if the PC was rebooted, adding an additional 10.000 rows took 30 seconds, which is nowhere in line with 1M rows in 10s. The reason for this is that SQLite has to read a very large part of the existing

Is C++ bimap possible with one side of view having different key than other side of the view value? How to do that?

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问题 At the beginning I needed a map, so I used std::map. Then, some requirements were added and I needed to also get "keys" for "value" (foos for bar), so I used boost::bimaps::bimap< boost::bimaps::unordered_set_of<boost::bimaps::tagged<std::string, foo>>, boost::bimaps::multiset_of<boost::bimaps::tagged<std::string, bar>>> And after that, some more requirements were added, so now I need to store a number for every foo and from the right side view I need to be able to call <bimap>.righ.find(bar)

数据库介绍与分类

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第1章数据库介绍与分类 1.1 数据库介绍什么是数据库简单的说，数据库就是一个存放计算机数据的仓库，这个仓库是按照一定的数据结构（数据结构是指数据的组织形式或数据之间的联系）来对数据进行组织和存储的，我们可以通过数据库提供的多种方法来管理其中的数据。 1.2 数据库的种类按照早期的数据库理论，比较流行的数据库模型有三种，分别为层次式数据库、网状数据库和关系型数据库。而在当今的互联网企业中，最常用的数据库模式主要有两种，即关系型数据库和非关系型数据库。 1.2.1 关系型数据库介绍（1）关系型数据库由来虽然网状数据库和层次数据库已经很好地解决了数据的集中和共享问题，但是在数据独立和抽象级别上仍有很大欠缺。用户在对这两种数据库进行存取时，仍然需要明确数据的存储结构，指出存取路径。而关系数据库就可以比较好地解决这些问题。（2）关系型数据库介绍关系型数据库模型是把复杂的数据结构归结为简单的二元关系（即二维表格形式）。在关系型数据库中，对数据的操作几乎全部建立在一个或多个关系表格上，通过这些关联的表格分类、合并、连接或选取等运算来实现数据的管理。关系型数据库诞生距今已有40多年了，从理论产生到发展到实现产品，例如：常见的MySQL和Oracle数据库，oracle在数据库领域里上升到了霸主地位，形成每年高达数百亿美元的庞大产业市场，而MySQL也是不容忽视的数据库

Use Python to manipulate txt file presentation of key-value grouping

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问题 I am trying to use Python in order to manipulate a text file from Format A: Key1 Key1value1 Key1value2 Key1value3 Key2 Key2value1 Key2value2 Key2value3 Key3... Into Format B: Key1 Key1value1 Key1 Key1value2 Key1 Key1value3 Key2 Key2value1 Key2 Key2value2 Key2 Key2value3 Key3 Key3value1... Specifically, here is a brief look at the file itself (only one key shown, thousands more in the full file): chr22:16287243: PASS patientID1 G/G patientID2 G/G patient ID3 G/G And the desired output here:

Use Python to manipulate txt file presentation of key-value grouping

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How to split key, value from text file using pandas?

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问题 I'm having input text file like this : Input.txt- 1=88|2=1438|3=KKK|4=7.7|5=00|7=66|8=a 1=13|2=1388|3=DDD|4=157.73|6=00|7=08|8=b|9=k I want to split this key and value pairs and showing in the format like this : Output.txt- index[0] 1 88 2 1438 3 kkk 4 7.7 5 00 6 7 66 8 a 9 index[1] 1 13 2 1438 3 DDD 4 157.73 5 6 00 7 08 8 b 9 k see In the index[0] 6 and 9 th record's values are Blank because 6 is available in the other column but not in this. Like this in index[1] 5th record is Blank.

Python: list of dictionaries, how to get values of a specific key for multiple items of the list?

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问题 I have a list of dictionaries like: dict_list = [{'key1': 'dict1_value1', 'key2': 'dict1_value2', 'key3': 'dict1_value3'}, {'key1': 'dict2_value1', 'key2': 'dict2_value2', 'key3': 'dict2_value3'}, {'key1': 'dict3_value1', 'key2': 'dict3_value2', 'key3': 'dict3_value3'}, {'key1': 'dict4_value1', 'key2': 'dict4_value2', 'key3': 'dict4_value3'}, {'key1': 'dict5_value1', 'key2': 'dict5_value2', 'key3': 'dict5_value3'}] getting the value for 'key3' for the second list item is like: dict_list[1][

How do I load nested key value pairs from a properties file into a Java object using Spring?

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问题 I understand how to use Spring with the PropertyPlaceholderConfigurer to load a .properties file when we know what properties to expect, and use @Value to store those values into variables or some object. However, how do I have Spring load up a properties file with nested key,value pairs when the keys can vary? For example, lets say I had the following car.properties file: Chevy=Corvette:String,1234567890:long,sportsCar:String Honda=Odyssey:String,2345678910:long,minivan:String Ford=F350

Reassignment, mutation, reference types, and value types

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问题 How would you appropriately explain why these two examples differ? // Reassignment let a = 1; let b = a; a = 2; console.log(b); // → 1 // Mutation let myArray = [1, 2, 3]; let ourArray = myArray; ourArray[2] = 10; console.log(myArray); // → [1, 2, 10] In regards to why the variable label behaves differently between the two, many resources claim that it's because of the difference between reference types and value types. But, doesn't that only apply to the differences between the values

Java disk-based key-value storage

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问题 Is there an efficient Java implementation of a filesystem-based key-value storage with the following features: Store, overwrite, and retrieve byte arrays by a unique ID (may be assigned by the storage) No memory caching (read means read from file system, write means write to file system immediately) Total data size up to few terabytes Number of stored objects up to hundreds of millions Manageable number of file system objects (to move/copy/delete entire storage on file system level) Will