Programmer Group

1. introduction When there is a large amount of data in a table, it is natural for us to think of splitting the table into many small tables. When we execute the query, we go to each small table to query. Finally, we summarize the data set and return it to the caller to speed up the query. For example, the order table and inventory table of e-c ...

Let's start with the most authentic definition If there is object o2 of type T for each object o1 of type S, so that when all object o1 defined by T is replaced by o2, the behavior of program P does not change, then type S is a subtype of type T. Let's look at a simple definition: All references to base classes must be able to use objects of t ...

1, SELECT clause /* Basic query: select * from Table name [where condition]; select Field list from table name [where condition]; Extended query, 5 clauses of select statement: (1)where where Condition is used to filter out the qualified records (rows) from the table (2)group by (3)having (4)order by (5)limit These five clauses can appea ...

HPA is the implementation of horizontal scaling in k8s. There are many ideas that can be used for reference, such as delay queue, time series window, change event mechanism, stability consideration and other key mechanisms. Let's learn the key implementation of the big guys together 1. Basic concepts As the implementation of general horizontal ...

demand The demand is like this: for example, background statistics show a relatively large total amount, such as 90,000,000, or more than 900 million. Need to show on the page again: xxxxbillion xxx10,000 XXX yuan, Amount value for statistics: If it's a billion then it's xxx10,000 XXX yuan, If it's 0 yuan, it's XXXX billion xxx million If it i ...

1. Lock API 1. Locks package class hierarchy 2. Lock interface Method Signature describe void lock(); Acquire locks (endless) boolean tryLock(); Acquire locks (just try it) boolean tryLock(long time, TimeUnit unit) throws InterruptedException; Acquire locks (out of date) void lockInterruptibly() throws InterruptedException; Acquire ...

Statistics of the amount of data in a table is a common requirement, but different table designs and different writing methods can lead to large differences in statistical performance. Here is a simple experiment to test (everyone should pay attention to the cache when testing, otherwise the test results will be affected). 1. Preparations In or ...

Child leetcode Longest Palindromic Substring Because I love it. 1005 longest palindrome The longest palindrome string is a string that reads the same from left to right or from right to left. Obviously, the string is left and right symmetrical, so we can find the large string through the small string. For example, the two s ...

1 Overview Composite Pattern refers to the grouping of a class of objects with common abstractions into a tree structure to represent the part-whole relationship. 2 Combination mode Often we encounter objects with the same behavior and hierarchical structure between them.In this case, the combination mode can make the system highly cohesive and ...

python data analysis personal study reading notes - Catalog Index Chapter 4 statistics and linear algebra Statistics and linear algebra lay the foundation for exploratory data analysis. Both descriptive and inferential statistical methods are helpful to obtain insights and inferences from the original data. For example, after calculating the ...