teleren/devto huggingface dataset:
Using the booted Method in Laravel Eloquent Models for CRUD Event Listening and Cache Resetting
Tags: webdev, php, laravel, blog
Published: 2023-03-14 05:36:19

## Introduction to the booted method in Eloquent

In Laravel's Eloquent ORM, the booted method is called when an Eloquent model is instantiated. This method provides a convenient place to register event listeners or perform other setup tasks.

By using the booted method, you can keep your model logic organized and easy to maintain. In this post, we'll explore how to use the booted method to listen for CRUD events and reset cache when creating or updating a model.


Lets understand it using example:

Suppose you have a Laravel application with a `User `model that is frequently accessed and updated. To speed up queries and reduce database load, you decide to cache user data using Laravel's Cache façade.

To cache user data, you'll need to store it using a unique cache key. You could use the user's ID as the cache key, but what happens when the user's data changes? You'll need to update the cache key every time the user is updated to ensure that the cache is not stale.

To automate this process, you can use the booted method to listen for the `creating `and `updating `events on the `User `model, and reset the `cache `for the user being created or updated.

## Registering event listeners

To listen for CRUD events, you can register event listeners using the `creating`, `created`, `updating`, `updated`, `saving`, `saved`, `deleting`, and `deleted` methods on the model's static boot method.

In this example, we'll use the `creating `and `updating` events to reset cache for the user being created or updated.

Here's how you can define event listeners in the boot method of the User model:


```
<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Model;
use Illuminate\Support\Facades\Cache;

class User extends Model
{
    protected static function booted()
    {

        static::creating(function ($user) {
            Cache::forget('user_' . $user->id);
        });

        static::updating(function ($user) {
            Cache::forget('user_' . $user->id);
        });
    }
}

```

## Resetting cache

To reset cache for a model, you can use Laravel's Cache facade. The Cache facade provides a simple API for storing and retrieving data from a variety of cache backends.

For example, to cache a user model by their ID, you can use the remember method of the Cache façade:


```
$userId = 1;

$user = Cache::remember('user_' . $userId, $minutes, function () use ($userId) {
    return User::find($userId);
});

```

In the above code, the remember method caches the user model with ID 1 for the specified number of minutes. If the cache is not already set, the closure passed to remember is called to retrieve the data and cache it.

To reset cache for a user when they are created or updated, we use the forget method


Conclusion

In this post, we've explored how to use the booted method in Eloquent models to listen for CRUD events and reset cache when creating or updating a model. By using event listeners and the Cache façade, you can keep your model logic organized and easy to maintain.
Difference between image and container in docker?
Published: 2023-03-14 05:30:24

In Docker, an image is a read-only template that contains the instructions for creating a Docker container. It includes the application code, runtime environment, libraries, and other dependencies required to run an application. An image is like a snapshot of an application at a specific point in time.

A container, on the other hand, is a running instance of an image. It's a lightweight and portable executable package that includes everything needed to run an application, including the code, runtime environment, and system tools. When you run a container, Docker creates a writable layer on top of the image, allowing the application to store data and make changes to the container's environment.

Here are some key differences between an image and a container in Docker:

Image is a static entity, while container is a dynamic entity: An image is a snapshot of an application at a specific point in time, and it can be stored, shared, and used to create multiple containers. A container, on the other hand, is a running instance of an image, with a dynamic state that can change over time as the application runs.

Image is read-only, while container is writable: An image is a read-only template that cannot be modified once it's created. A container, on the other hand, has a writable layer on top of the image, which allows the application to store data and make changes to the container's environment.

Image can be shared, while container is ephemeral: An image can be shared between multiple systems or users, and it can be used to create multiple containers. A container, on the other hand, is an ephemeral instance of an image, and it only exists as long as the application is running.

Image defines the application, while container executes the application: An image contains the application code, runtime environment, and dependencies, while a container is responsible for executing the application based on the instructions defined in the image.

In summary, an image is a static template that defines the application, while a container is a dynamic instance of an image that executes the application and can be modified and interacted with during runtime.
What is a Kernel in Operating System in a nutshell?
Published: 2023-03-14 05:20:57

The kernel of Linux is the heart of the operating system that controls and manages all system resources.
In order to understand kernel better you can think of things which it is not, in other words if kernel is a part of OS then what else is there in OS which it is not.

A kernel is not:

- User Interface
- System Services
- File System
- Device Drivers
- Utilities
- Applications

User Interface: The user interface (UI) is the part of the operating system that allows users to interact with the system. This can include graphical user interfaces (GUIs), command-line interfaces (CLIs), or other types of interfaces.

System Services: The system services are a set of background processes and services that provide additional functionality to the operating system. These can include network services, printing services, security services, and more.

File System: The file system is a hierarchical structure that is used to organize and store files and directories on disk. The file system provides a standard interface for accessing and managing files, and it includes features like permissions, file attributes, and file locking.

Device Drivers: Device drivers are software components that allow the operating system to communicate with hardware devices like printers, scanners, and network adapters. These drivers provide an interface between the hardware and the operating system, allowing applications to use the hardware without needing to know the details of how it works.

Utilities: Utilities are small programs that provide additional functionality to the operating system. These can include things like text editors, system monitors, and command-line tools.

Applications: Finally, an operating system includes a variety of applications that are used to perform common tasks like browsing the web, sending email, and creating documents.

All of these components work together to provide a complete and functional environment for running applications and managing system resources.

In summary, the kernel of an operating system is the core component that manages system resources and provides services to user-level processes and applications. The Linux kernel is a concrete example of a kernel that provides a stable, efficient, and versatile environment for running a wide range of applications and services.
Field Design
Tags: opengauss, database
Published: 2023-03-14 04:54:13

To improve query efficiency, comply with the following rules when designing columns:

**·** [Proposal] Use the most efficient data types allowed.

If all of the following number types provide the required service precision, they are recommended in descending order of priority: integer, floating point, and numeric.

**·** [Proposal] In tables that are logically related, columns having the same meaning should use the same data type.

**·** [Proposal] For string data, you are advised to use variable-length strings and specify the maximum length. To avoid truncation, ensure that the specified maximum length is greater than the maximum number of characters to be stored. You are not advised to use CHAR(n), BPCHAR(n), NCHAR(n), or CHARACTER(n), unless you know that the string length is fixed.

For details about string types, see Common String Types.

**Common String Types**
Every column requires a data type suitable for its data characteristics. The following table lists common string types in openGauss.

Table 1 Common string types

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/y4e59br3p1fr9uch9r6r.png)
Table Design
Tags: opengauss, database
Published: 2023-03-14 04:52:27

Comply with the following principles to properly design a table:

**·** [Notice] Reduce the amount of data to be scanned. You can use the pruning mechanism of a partitioned table.
**·** [Notice] Minimize random I/Os. By clustering or local clustering, you can sequentially store hot data, converting random I/O to sequential I/O to reduce the cost of I/O scanning.

**Selecting a Storage Mode**
[Proposal] Selecting a storage model is the first step in defining a table. The storage model mainly depends on the customer's service type. For details, see Table 1.

Table 1 Table storage modes and scenarios

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/zsr8s65efjkpclcz1jk1.png)

**Selecting a Partitioning Mode**
If a table contains a large amount of data, partition the table based on the following rules:

**·** [Proposal] Create partitions on columns that indicate certain ranges, such as dates and regions.
**·** [Proposal] A partition name should show the data characteristics of a partition. For example, its format can be Keyword+Range characteristics.
**·** [Proposal] Set the upper limit of a partition to **MAXVALUE** to prevent data overflow.
The example of a partitioned table definition is as follows:

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/0uis7luo7cwuke47at9a.png)
Database and Schema Design
Tags: opengauss, database
Published: 2023-03-14 04:50:18

In openGauss, services can be isolated by databases and schemas. Databases share little resources and cannot directly access each other. Connections to and permissions on them are also isolated. Schemas share more resources than databases do. User permissions on schemas and subordinate objects can be controlled using the **GRANT** and **REVOKE** syntax.

**·** You are advised to use schemas to isolate services for convenience and resource sharing.
**·** It is recommended that system administrators create schemas and databases and then assign required permissions to users.

**Database Design**

**·** [Rule] Create databases as required by your service. Do not use the default **postgres** database of a database instance.
**·** [Proposal] Create a maximum of three user-defined databases in a database instance.
**·** [Proposal] To make your database compatible with most characters, you are advised to use the UTF-8 encoding when creating a database.
**·** [Notice] When you create a database, exercise caution when you set **ENCODING** and **DBCOMPATIBILITY** configuration items. openGauss supports the A, B, C, and PG compatibility modes, which are compatible with the Oracle syntax, MySQL syntax, Teradata syntax, and Postgres syntax, respectively. The syntax behavior varies according to the compatibility mode. By default, the A compatibility mode is used.
**·** [Notice] By default, a database owner has all permissions for all objects in the database, including the deletion permission. Exercise caution when deleting a permission.

**Schema Design**
**·** [Notice] To let a user access an object in a schema, assign the usage permission and the permissions for the object to the user, unless the user has the **sysadmin** permission or is the schema owner.
**·** [Notice] To let a user create an object in the schema, grant the create permission for the schema to the user.
**·** [Notice] By default, a schema owner has all permissions for all objects in the schema, including the deletion permission. Exercise caution when deleting a permission.
Database Object Naming Conventions
Tags: opengauss, database
Published: 2023-03-14 04:47:35

The name of a database object must meet the following requirements: The name of a non-time series table ranges from 1 to 63 bytes and that of a time series table ranges from 1 to 53 characters. The name must start with a letter or underscore (_), and can contain letters, digits, underscores (_), dollar signs ($), and number signs (#).

**·** [Proposal] Do not use reserved or non-reserved keywords to name database objects.

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/z6t46snpc438apkpqgzr.png)

**·** [Proposal] Do not use a string enclosed in double quotation marks ("") to define the database object name, unless you need to specify its capitalization. Case sensitivity of database object names makes problem location difficult.

**·** [Proposal] Use the same naming format for database objects.

**-** In a system undergoing incremental development or service migration, you are advised to comply with its historical naming conventions.
**-** You are advised to use multiple words separated with underscores (_).
**-** You are advised to use intelligible names and common acronyms or abbreviations for database objects. Acronyms or abbreviations that are generally understood are recommended. For example, you can use English words or Chinese pinyin indicating actual business terms. The naming format should be consistent within a database instance.
**-** A variable name must be descriptive and meaningful. It must have a prefix indicating its type.

**·** [Proposal] The name of a table object should indicate its main characteristics, for example, whether it is an ordinary, temporary, or unlogged table.

**-** An ordinary table name should indicate the business relevant to a dataset.
**-** Temporary tables are named in the format of **tmp_**Suffix.
**-** Unlogged tables are named in the format of **ul_**Suffix.
**-** Foreign tables are named in the format of **f_**Suffix.
**-** Do not create database objects whose names start with **redis_**.
**-** Do not create database objects whose names start with **mlog_** or **matviewmap_**.

**·** [Proposal] The name of a non-time series table object shall not exceed 63 bytes. If the length exceeds this value, the kernel truncates the table name. As a result, the table name is inconsistent with the configured name. In different character sets, characters may be truncated and unexpected characters may appear.
Development and Design Proposal
Tags: opengauss, database
Published: 2023-03-14 04:42:19

This section describes the design specifications for database modeling and application development. Modeling based on these specifications can better fit the processing architecture of openGauss and output more efficient service SQL code.

The meaning of “Proposal” and “Notice” in this section is as follows:

**· Proposal**: Design rules. Services complying with the rules can run efficiently, and those violating the rules may have low performance or logic errors.
**· Notice**: Details requiring attention during service development. This term identifies SQL behavior that complies with SQL standards but users may have misconceptions about, and default behavior that users may be unaware of in a program.
Step by step guide for Creating a NodeJS Application for Novice
Published: 2023-03-14 04:41:25


Here are the simple step by step guide to create a NodeJS application.

1. Install Node.js: First, you need to download and install Node.js on your computer. You can download the latest version of Node.js from their official website https://nodejs.org/en/.

2. Create a new folder: Create a new folder where you want to store your Node.js application files.

3. Initialize a new Node.js project: Open the command prompt or terminal, navigate to the folder you just created, and run the following command:
`npm init`
This command will prompt you to enter some basic information about your project, such as the name, version, description, entry point, and so on. You can either accept the default values or enter your own.

4. Install necessary packages: Depending on your project's requirements, you may need to install additional packages or libraries. For example, if you are building a web application, you may need to install the Express.js framework. You can install packages using the following command:
 `npm install express`
5. Create a JavaScript file: Create a new file in your project folder and name it index.js. This will be the entry point of your application.

6. Write your Node.js application code: Open the index.js file in your code editor and start writing your Node.js application code. Here is a simple example:

```
const express = require('express');
const app = express();

app.get('/', (req, res) => {
  res.send('Hello World!');
});

app.listen(3000, () => {
  console.log('Server started on port 3000');
});

``` 
 
This code creates a new Express.js application, sets up a basic route that sends a "Hello World!" message to the client when the root URL is requested, and starts the server on port 3000.

Run your Node.js application: Open the command prompt or terminal, navigate to your project folder, and run the following command:
`node index.js`
 This will start your Node.js application and you should see the "Server started on port 3000" message in the console.


That's it! You have now created a basic Node.js application. Of course, this is just the beginning. There is a lot more you can do with Node.js, so keep learning and experimenting!
Working with Databases-Creating and Managing Sequences
Tags: opengauss, database
Published: 2023-03-14 04:38:55

**Background**
A sequence is a database object that generates unique integers. Sequence numbers are generated according to a certain rule. Sequences are unique because they increase automatically. This is why they are often used as primary keys.

You can create a sequence for a column in either of the following methods:

**·** Set the data type of a column to sequence integer. A sequence will be automatically created by the database for this column.
**·** Run the CREATE SEQUENCE statement to create a sequence. Set the initial value of the **nextval**('sequence_name') function to the default value of a column.

**Procedure**
Method 1: Set the data type of a column to a sequence integer. For example:

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/3udv6sm6lydhoqmg0dsb.png)

If the following information is displayed, the table has been created:

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/aax0r0ababt5ueyr34rb.png)

Method 2: Create a sequence and set the initial value of the **nextval**('sequence_name') function to the default value of a column.

1. Create a sequence.

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/jrwt6zraxu29rv1mqutv.png)

If the following information is displayed, the sequence has been created:

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/ripeottxnlb50kccbato.png)

2. Set the initial value of the **nextval**('sequence_name') function to the default value of a column.

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/1l42vls9zjua9jnrben6.png)

If the following information is displayed, the default value has been specified:

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/2qyrv4gpp187iohhcpko.png)

3. Associate the sequence with a column.

Associates a sequence with a specified column included in a table. In this way, the sequence will be deleted when you delete its associated column or the table where the column belongs to.

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/j7ip5xj7aoxcory1aawz.png)

If the following information is displayed, the column has been specified:

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/mvs4jfnmsx7d0lvcw4z7.png)

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/qq7gq1zs10yyu0kym862.png)
Tips and tricks for debugging code
Published: 2023-03-14 04:00:00

 Debugging Code: Tips and Tricks for Finding and Fixing Errors

Debugging code is an essential part of the software development process. No matter how experienced you are, you will inevitably encounter errors and bugs in your code at some point. In this post, we'll go over some tips and tricks for debugging code that will help you find and fix errors more efficiently.

Use a debugger: A debugger is a tool that allows you to step through your code line by line, inspect variables, and set breakpoints. Using a debugger can help you identify the root cause of an error and find the exact line of code that is causing the problem.
Use print statements: Print statements are a simple but effective way to debug code. By inserting print statements at various points in your code, you can see the values of variables and the flow of execution, which can help you identify where an error is occurring.
Test your code incrementally: When you're working on a large project, it can be helpful to break it down into smaller pieces and test each piece individually. This way, you can more easily identify where an error is occurring, rather than trying to find it in a large and complex codebase.
Use version control: Version control systems like Git allow you to track changes to your code and revert back to previous versions if needed. This can be particularly helpful if you make a change that introduces an error, as you can easily revert back to a previous version that was working correctly.
Ask for help: If you're stuck and can't seem to find the cause of an error, don't be afraid to ask for help. Whether it's a colleague, a mentor, or an online forum, there are many resources available that can help you troubleshoot your code.
Conclusion

Debugging code can be frustrating, but it's an essential part of the software development process. By using tools like debuggers, print statements, and version control, and by breaking your code down into smaller pieces and asking for help when needed, you can more effectively find and fix errors. With practice and patience, you'll get better at debugging and be able to solve even the most challenging problems.