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background In previous articles Analysis and solution of DataSourceScanExec NullPointerException caused by spark DPP , we directly skipped the step of dynamic code generation failure. This time, let's analyze that SQL is still in the article mentioned above. analysis After running the sql, we can see the following physical plan: We can see ...

Double pointer Double pointer is an idea or a skill, not a specific algorithm. Specifically, we use two variables to dynamically store two nodes to facilitate some operations. Usually used in linear data structures. Especially for the problems of linked list, it is often necessary to use two or more pointers to memorize the nodes on the linke ...

Judge by document type Test options Test optionseffect-bJudge whether the file exists and whether it is a block device file (yes, the block device file is true)-cJudge whether the file exists and whether it is a character device file.-dJudge whether the file exists and whether it is used as a directory file.-eDetermine whether the file ex ...

demand The performance of the server is relatively good. I want to run programs conveniently on the server, so I establish jupyter on the server, and then access the jupyter web page locally through connection for operation; In addition, I want to be familiar with nginx and facilitate the construction of websites later. nginx A more popular bac ...

SQL, namely structured query language, is a database query and programming language, which is used to access data and query, update and manage relational database system; SQL language is the widely used standard language of relational database and the basis of various database interaction methods. The following will show how to use SQL to acces ...

Message queue Pipes and shared memory: byte stream data Message: datagram (type + data) Queues: priority queues You can specify the type to read. Under the same type, it is in the order of first in first out Operation of message queue: 1. Create and access a message queue #include <sys/types.h> #include <sys/ipc.h> #include <s ...

catalogue 1, Introduction 2, Color recognition principle 3, Functional module design 4, Coverage calculation process 5, Software implementation effect 1, Introduction With the continuous strengthening of the national awareness of ecological and environmental protection, the balance of grassland grass and livestock has been paid more a ...

C + + singleton mode and thread safety The simplest singleton mode can be // single thread safe version class Singleton { public: static Singleton* GetInstance(int x = 0) { if (instance_ == NULL) { instance_ = new Singleton(x); } return instance_; } void Print() { ...

Solve the problem that WebClient calls cannot be tracked in the Spring Cloud Gateway projectProblem descriptionSkywalking brings non intrusive distributed link collection to java applications through java agent. In the microservice architecture, as a business Gateway, Spring Cloud Gateway generally needs to customize the Filter and call other ...

1, View 1. What is a view The view is to get a virtual table through query, then save it and use it directly next time 2. Why use views If you want to use a virtual table frequently, you can avoid repeated queries 3. How to use views create view teacher2course as select * from teacher inner join course on teacher.tid = course.teacher_id; be ...