Скачать или смотреть Solving the NodeJS MySQL INSERT and SELECT Sync Issue

Discover how to effectively manage asynchronous MySQL queries in Node.js to ensure reliable data operations without using timeouts.
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This video is based on the question https://stackoverflow.com/q/74651256/ asked by the user 'Synaptic' ( https://stackoverflow.com/u/20484270/ ) and on the answer https://stackoverflow.com/a/74652631/ provided by the user 'Synaptic' ( https://stackoverflow.com/u/20484270/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Introduction

In the world of web development, especially when working with databases, managing data insertion and retrieval can sometimes lead to unexpected behaviors. If you've ever faced issues where SELECT queries return inconsistent results immediately after an INSERT, you're not alone. This guide dives into a common problem encountered by developers using Node.js with MySQL and shares a streamlined solution.

The Problem

Imagine a scenario where you need to insert data into a MySQL database table and then immediately select that data for further processing. In a specific case, the developer experienced intermittent failures: the SELECT query following an INSERT would not always return results. This unpredictability raised concerns over database query timing and execution order, ultimately leading to frustrating debugging sessions.

Use Case Overview

Three MySQL queries in total:

Two SELECT queries

One INSERT query

The first SELECT query behaves as expected.

The second SELECT query returns empty results intermittently.

The developer is using mysql2 with a connection pool.



The Solution

After digging deeper, it was discovered that introducing a small setTimeout in the insertion function helped synchronize query execution, eliminating the inconsistent behavior. Here’s a comprehensive breakdown of the solution.

Step 1: Modify the Insert Function

The original insertion function was good, but adding a delay using setTimeout resolved the issues. Here's how the insert function was modified:

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Addressing the Timeout Concerns

While a setTimeout effectively solved the immediate issue, it raised a valid concern: What if the operation required more or less time to complete based on the server or data volume? To make this solution more reliable:

Dynamic Timing: Instead of a fixed timeout, calculate actual time taken by the insertion queries before calling resolve().

Promises with Callbacks: Ensure that each asynchronous operation, especially the insertion, properly returns a promise that you can await before proceeding to the next query.

Here's a refined approach:

[[See Video to Reveal this Text or Code Snippet]]



Conclusion

Managing asynchronous operations in Node.js when interacting with MySQL can be tricky, especially regarding the timing of queries. By understanding and resolving these timing issues, you can ensure consistent behavior in your applications.

The solution we discussed shows a straightforward way to sync your INSERT and SELECT operations effectively. Remember, while short fixes like setTimeout can offer immediate relief, aim for more robust solutions that dynamically handle such scenarios for long-term stability.

Feel free to explore more about asynchronous programming in Node.js and MySQL practices to further improve your coding skills!