red hat linux64
After installing gi software and oralce database software, the database is built through the dbca user interface. It is found that the database can be built normally on node1, not on node2. The dbca library building process errors on node2.
Posted by scottrad on Sun, 05 Jul 2020 17:42:16 +0200
[select] SQL statement query
join(left/right) two-table join/multi-table join
//Multi-table Joint Survey:
$sql = 'SELECT * FROM news LEFT JOIN (news_type, news_photo)ON (news_photo.n_id=news.n_id AND n_type=news_type.id)';
//Joint investigation of two tables:
$sql = 'SELECT * FROM s LEFT JOIN sc ON s.sno=sc.sno';
Three Tables Joint Ch ...
Posted by gawrrell on Sun, 05 Jul 2020 17:37:13 +0200
Oozie is an open source framework based on workflow engine contributed by Cloudera company to Apache. It is an open source workflow scheduling engine of Hadoop platform, which is used to manage Hadoop jobs. This article, the first in a series, introduces oozie's task submission phase.
We deduce the implementation f ...
Posted by cowboy_x on Tue, 30 Jun 2020 05:26:29 +0200
Singleton mode is one of the creation modes. In our software development process, there are many classes that are only created once globally, such as app framework class, global management class, configuration file, log, database, etc. Using singleton mode can make our code elegant.
The UML class diagram and C++ sample code are given below:
Posted by mightymaster on Mon, 29 Jun 2020 18:15:58 +0200
1, Private key
in this lesson, we will continue to register the Token, which is to backup the private key. Each public chain will have a private key, but it is different. There are four private keys in MAC. namely
Wallet key is one of the necessary information to open MAC wallet. ...
Posted by doodmon on Mon, 29 Jun 2020 10:36:56 +0200
1. What is a deadlock? What's the harm?
1.1 what is deadlock?
Occurs in concurrency
[mutually exclusive]: when two (or more) threads (or processes) hold each other's resources required by each other, but do not actively release them, all of them can't move forward, resulting in endless blocking o ...
Posted by ollmorris on Mon, 29 Jun 2020 08:23:19 +0200
Durid is a widely used database connection pool, which has superior performance, powerful monitoring mechanism, and also supports expansion through the mechanism of filter.
Druid has a StatFilter for slow sql recording, but I found some shortcomings in using it:
The print log of this Fi ...
Posted by jonsof on Mon, 29 Jun 2020 04:13:38 +0200
stay RocketMQ repeated consumption problem | the introduction of idempotent mechanism into the core process of order system In this paper, we discuss the problem of repeated message consumption. A better solution is to use business judgment on the consumption side to ensure the idempotence of the interface, so as to avoid the problem of repeate ...
Posted by GaryE on Sat, 27 Jun 2020 10:41:09 +0200
1 multi meter
1.1 multi table description
In actual development, a project usually needs many tables to complete
For example, the database of a shopping mall project needs many tables: user table, classification table, commodity table, order table
1.2 disadvantages of single table
1.2.1 table building
Posted by powaz on Sat, 27 Jun 2020 10:16:57 +0200