Tag:data

  • Simple exploration of data internal storage structure of SQL Server

    Time:2020-7-13

    Databases often need to deal with each other, but never thought about how to store data inside the database. Today, we will explore how to store data in the database from the following aspects How to store data in database How to store index data Operational data impact on storage summary How to store data […]

  • Deep comparative data science Toolbox: sparkr vs sparklyr

    Time:2020-7-13

    Background Sparkr and sparklyr are two spark based R language interfaces, which are deeply integrated into R language ecology through simple syntax. Sparkr is maintained by the spark community. The latest functions of sparkr are updated through the source code level. It was initially supported from version 1.5 in the summer of 2016. It is […]

  • Lock [implementation of InnoDB isolation]

    Time:2020-7-13

    Global lock Table level lock Row level lock The locks in MySQL can be roughly divided into global locks, table level locks and row locks. Global lock and table lock are server level, row level lock is storage engine level, only InnoDB supports row and lock. Global lock: It is to lock the entire database […]

  • Tensorflow reads binary files

    Time:2020-7-13

    1. Build file list and use cifar-10 dataset path=’./data/cifar/’ file_names=os.listdir(path) file_list=[os.join(path,file_name) for file_name in file_names if file_name.endswith(‘.bin’)] 2. Open the queue to read the file list queue_list=tf.train.string_input_producer(file_list) 3. Build a reader to read data reader=tf.FixedLengthRecordReader(self.bytes) key,value=reader.read(queue_list) 4. Analyze the data label_iamge=tf.decode_row(value,tf.uint8) 5. Cut the data into eigenvalues and target values label = tf.slice(label_image, [0], [self.label_bytes]) […]

  • Redis transactions

    Time:2020-7-13

    1、 What is it Multiple commands can be executed at a time, which is essentially a set of commands. All commands in a transaction are serialized,It is not allowed to be inserted serially 2、 What can I do In a queue, one-time, sequential execution of a series of commands 3、 Sample demonstration Normal execution 127.0.0.1:6379 […]

  • Understand cache penetration and cache avalanche, and learn more about cache breakdown!

    Time:2020-7-13

    The difference between cache breakdown and cache avalanche is that the avalanche targets many keys, while the breakdown only targets a certain hot key. Setting the cache to never expire. Although this method is very violent, it can solve most problems. Of course, most scenarios are not suitable; Setting the random expiration time is not […]

  • Simply sort @ requestparam and @ requestbody

    Time:2020-7-13

    The front-end transmits parameters to the back-end, and how the back-end receives them will be thought ofspringNotes for Before that, I used it all the timeRequestParam(“userName”) String userName It’s not very useful to be reasonableRequestParam String userName It’s time to see the difference between the two @RequestParam @Requestbody (received as JSON data) If you don’t […]

  • Nightware: a crawler framework based on electron

    Time:2020-7-13

    Author: WilliamThis article is an original article, please indicate the author and source Electron allows you to use pure JavaScript to call Chrome’s rich native interface to create desktop applications. You can think of it as a desktop focused app Node.js Instead of a web server. Its browser based application mode can make all kinds […]

  • C ා to update the query table as a parameter to the database

    Time:2020-7-13

    1. Main method of importdata Put the input as the object array type, and take out the corresponding parameters according to the subscript. Here are table and username public object[] ImportData(object[] Param) { DataTable dt = (DataTable)Param[0]; string msg1 = “”, msg2 = “”, msg3 = “”; Hashtable ht = new Hashtable(); Username = param […]

  • C ා implement excel operation — add tab sheet

    Time:2020-7-11

    C ා implements the operation on Excel, which will be placed in different tabs according to different types or sources of data. The code of tab added by C ා implementation is as follows: (path is the address where the document is saved, DT is the source data to be processed) public void addSheet(string Path, […]

  • How to update variables in real time in Flink datastream operator?

    Time:2020-7-11

    1. Problem description, as shown in the following figure:When writing machine learning algorithms, I encounter a scenario where the variable currentcenter is needed in the first map, and then the result I output needs to update the current center (the last map), but there is no way to update it. Because the map function is […]

  • Introduction to spark

    Time:2020-7-11

    Spark introductory learning resources: Spark introduction series of experimental courses. 1、 About spark: Spark is a cluster computing framework developed by UC Berkeley amp lab, which is similar to Hadoop, but has many differences. The biggest optimization is that the intermediate results of computing tasks can be stored in memory, and it does not need […]