MyBatis level 1 cache implementation details and precautions

Introduction to L1 cache In the process of application running, it is possible for us to execute multiple SQL queries with the same query conditions in a database session. MyBatis provides the scenario of optimizing the first level cache. If the SQL statements are the same, the first level cache will be hit first, so as to avoid directly queryi ...

Posted by phpORcaffine on Sun, 26 Apr 2020 09:16:35 -0700

Spark DataFrame is not a real DataFrame

The article was originally written in Mars team column , welcome to follow. From this article, we start a new series of reading paper. Today's paper is Towards Scalable Dataframe Systems , is still a preprint. By Devin Petersohn from Riselab , formerly known as APMLab, the lab has produced a series of famous open source projects, such as Apache ...

Posted by daniel_grant on Sun, 26 Apr 2020 00:52:37 -0700

PLSQL syntax (variable, if,loop,cursor,exception)

1. Grammar Break executable method saved on the database server for other developers to call It can effectively reduce the data interaction between database and server, improve efficiency and reduce bandwidth consumption Syntax format: declare -- define part, save variable, reference variable, record exception begin -- logical processing ...

Posted by wint.thaw on Sat, 25 Apr 2020 08:08:26 -0700

Log4j output log to separate log file

  Log4j output log to separate log file 09:01:03, January 31, 2018 Number of readings: 1065 Under normal circumstances, the info log of log4j will be printed to a unified log file. When you need to view the execution of a specific function, print a specific function to a specific ...

Posted by rajah on Sat, 25 Apr 2020 07:31:37 -0700

Django ORM multi table operation (Advanced)

  Django ORM multi table operation (Advanced)   1, Create model Next, we design the corresponding relationship between each table through the book management system. Through the relationship above, we can define our model class. from django.db import models class Book(models.Model): title = models.CharField(max_length= ...

Posted by bough on Fri, 24 Apr 2020 22:45:19 -0700

Take you to the Quick Start-Advanced-Advanced ybatis-XML Approach

MyBatis-XML Schema 1. Brief Description - Differences from Notes Execution efficiency: same Speed of development: faster annotations Easy maintenance: Notes are simpler. Old company, old projects still use XML     2. Environmental Setup 1. Make sure the database has been created 2. Import jar package & core configuration file ...

Posted by morphboy23 on Fri, 24 Apr 2020 10:13:57 -0700

MySQL function of database

1, Date and time functions 1. Function to get the current dateIt's the same. It's different CURDATE(): used to get the current date of the systemCurrent "date() is used by the system to get the current date mysql> select CURDATE(),CURRENT_DATE(); 2. Get function of current time CURTIME(): used to get the current time of the system ...

Posted by deerly on Fri, 24 Apr 2020 10:12:24 -0700

Recommendation Engine for SparkML (2) - Evaluation of Recommendation Model

The content and code for this article follow Last article To write, we recommend that you take a look at Ha~.We wrote the implementation of the movie recommendation in the last article, but is the recommendation reasonable? This requires us to evaluate the model.For the recommended models, the models are evaluated based on the mean square devia ...

Posted by chiprivers on Thu, 23 Apr 2020 10:52:57 -0700

where clause of Oracle

The where clause is used to find records from tables or temporary datasets that meet the specified conditions, and can be used for conditions in select, update, and delete statements. 1, Generate test data Use the following SQL to create the super girl basic information table (t? Girl) and insert some test data. create table T_GIRL ( id ...

Posted by banacan on Thu, 23 Apr 2020 05:19:05 -0700

Laravel v7.7 publishing container supports variable parameters

The Laravel team yesterday released v7.7.0, which includes container supported constructors supporting variable parameters, some new HTTP client functions, Blueprint's new rawIndex() method and all the latest functions in the 7.x branch. Repair and change: HTTP client GET request support array Daniel Mason contributed to the HTTP client's suppo ...

Posted by busyguy78 on Thu, 23 Apr 2020 00:00:00 -0700