• Case analysis of establishing efficient index in MySQL


    This paper introduces how to build an efficient index with MySQL. The details are as follows: How to build an ideal index? Query frequency discriminative power Index length Override field discriminative power Assuming 1 million users and 50 W for each gender, the discrimination is low. The length is small Index length directly affects the […]

  • Conversion between list and array in Java


    List to Array List provides the interface of toArray, so it can be called directly and converted into an object type array List<String> list = new ArrayList<String>(); Object[] array=list.toArray(); The above method will throw exception when there is a cast. The following method is more recommended: YesSpecify the type String[] array=list.toArray(new String[list.size()]); Array to List […]

  • In and exists in Oracle


      In is a hash connection between the outer table and the inner table, while exists is a loop loop loop for the outer table. Each loop loop will query the inner table. It has always been considered that exists is more efficient than in. If the two tables queried are of the same size, […]

  • Real Python web interview experience (1)


    For your reference only.You can record the interview so that you can review the interview content and re-examine your shortcomings   1. Self introduction Here I will briefly describe where I graduated from, my last job, and the reason why I want to change my career. 2. Have you done the front end and back […]

  • Generate random files of fixed size


    Recently, there is a demand that requires a large number of files. 10000 files with a size of 1K are randomly generated seq 10000 | xargs -i dd if=/dev/zero of={}.dat bs=1024 count=1 The advantage of this method to generate random files is high efficiency (1g files are generated for about 1s), the size of the […]