Nodejs mysql promise

A Bluebird Promise that resolves to a connection object. A Bluebird Promise that resolves to a pool object. This function must either return the wrapped mysql object, return a promise of the wrapped mysql object or call the callback that is passed into the function. The main difference is that mysql. Besides this, the API is the same and you should be able to upgrade straight to v4. The only other difference is the extra options in the connectionOptions object.

Git github. API mysql. Parameters connectionOptions object : A connectionOptions object Return value A Bluebird Promise that resolves to a connection object mysql.

Function arguments mysql mysql object : The mysql object callback error, success function : A node-style callback that can be used to pass the wrapped version of the mysql object out of the wrapper function. Connection object methods connection. Pool object methods pool. Upgrading from v3 The main difference is that mysql. Keywords promise performance promises promises-a promises-aplus async await deferred deferreds future flow control dsl fluent interface database mysql mysql-promise bluebird q.

Install npm i promise-mysql Downloads Weekly Downloads 23, Version 4. License MIT. Unpacked Size Total Files 9. Homepage github. Repository Git github. Last publish 2 months ago. Try on RunKit. Report a vulnerability.GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together. Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Already on GitHub? Sign in to your account. Can node-mysql be used with promises, or only with callbacks? If it can't, can you suggest how best to use it within a promises structure? I'm a bit lost with promisify, bluebird, Q, This library uses callbacks because they are more performant and also let you do anything. If you want to use promises with callbacks, bluebird I know offers this functionality. Here is an example:. Would be nice to see some benchmarks. The time that promise resolution takes, in the context of roundtrips, is negligible.

Typescript & MySQL REST API (Nodejs & Express)

The only way to truely benchmark it would be to convert at least the external APIs in this module to promises and then make a benchmark suite and use it to compare this module with and without them. I'll post more detailed results later, but rough numbers for simple "select 1" x times: qps - node-mysql qps - promise-mysql qps - node-mysql2. So there is some overhead, probably less visible on bigger resultsets or slower queries. There is a big difference between node v0. On Dec 19,atAndrey Sidorov notifications github.

It would be interesting to test it using the native 0. It's been helpful following this discussion I prompted, but in fact I have the luxury of being in the position of planning future development rather than having to go live immediately, and am hoping that providing Node. I will be able to skip a generation, pass over promises, and go straight to generators using Koa with something like co-mysql or mysql-co. Using Koa at least, it seems that programs can be written almost as traditional synchronous code, just prefixing would-be blocking calls with 'yield', making for far more readable hence supportable code.

I find promises avoid 'callback-hell', but still break up code flow in unnatural ways. I believe error handling is also simpler and more robust with Koa.

There's a decent illustration here: www.

nodejs mysql promise

ES7 will give us async and await keywords, which will make promises look exactly like Koa and Koa plans to use promises as soon as this happens.

ES6 is available in Node v0. Koa uses generators "through leveraging generators Koa allows you to ditch callbacks". No need to wait for ES7. Generators are not a good candidate for MySQL abstraction. The co library hacks generators such that it provides a trampoline. I don't even understand why people make these modules - the bluebird docs provide an example how to promisify the mysql module with literally 2 lines using promisifyAll.Writing asynchronous applications in Node.

Accessing a database is an example of an operation which is asynchronous by nature. It means that you have to wait for the results of a query, but while waiting, your program will continue to execute. For example, it can do some calculations or send another query to the database in parallel. In a traditional, synchronous programming language like PHP, you could simply write:. In JavaScript, you have three options to write asynchronous code:. Using the await keyword:. At first, the difference seems purely cosmetic.

The differences become more obvious when you try to do something more complex. In my earlier article, Node. With promises, the code becomes more elegant, because you can chain multiple then handlers and use one catch handler for all errors. However, extracting the query results and closing the connection regardless of a success or error still requires some effort.

The situation becomes even worse when you have to introduce loops and conditions into an asynchronous code. Imagine the following hypothetical synchronous pseudocode:. Implementing this code asynchronously with callbacks would be hard and would make the code almost unreadable.

How to Interact With a Database Using Promises in Node.js

It uses traditional programming constructs, such as loop and conditionals, and the execution order becomes obvious. This makes it easier to see which error handler is associated with a particular block of code. An async function is simply nothing more than a function that is guaranteed to return a promise. You can use it like any other function which returns a promise:.

Node.js Promise Tutorial

On the other hand, within an async function, you can use the await keyword with any promise, not only to call other async functions:.

This will print 42 as well. But it works the same, so both the query and close functions return a promise. We can add support for transactions by promisifying the beginTransactioncommit and rollback functions in our database wrapper:.

nodejs mysql promise

The above code rewritten to use transactions looks like this:. To avoid repeating this boilerplate code every time, we can create a helper function which executes arbitrary asynchronous code within a transaction:. As you can see, the callback parameter is expected to be a function returning a promise.The MariaDB Node.

The default API is Promise. Callback is provided for compatibility with the mysql and mysql2 APIs. Documentation provided on this page uses the Promise API. It's not recommended, but in some cases, Node. Connection details such as URL, username, and password are better hidden into environment variables. Dotenv loads environment variables from. For more information, see the Connection option documentation.

When working with a local database that is, cases where MariaDB and your Node. If you don't know it off hand, you can retrieve it from the server. Pool options includes Connection option that will be used when creating new connections. Creates a new pool cluster. Pool cluster options includes pool option documentation that will be used when creating new pools.

To prevent SQL Injection attacks, queries permit the use of question marks as placeholders. The Connection escapes values according to their type. When streaming, objects that implement Readable are streamed automatically. But, there are two server system variables that may interfere:.

Queries return two different kinds of results, depending on the type of query you execute. Each value in the array is a returned row as a JSON object.

Those options can be set on the query level, but are usually set at the connection level, and will then apply to all queries. While the recommended method is to use the question mark placeholderyou can alternatively allow named placeholders by setting this query option.

Values given in the query must contain keys corresponding to the placeholder names. Using this option causes the Connector to format rows in the result-set as arrays, rather than JSON objects. Doing so allows you to save memory and avoid having the Connector parse column metadata completely.

Occasionally, you may have issue with queries that return columns with the same name. The standard JSON format does not permit key duplication. This causes the Connector to group data by table. Whether the query should return integers as strings when they are not in the safe range. In the event that you need certain values returned as a different type, you can use this function to cast the value into that type yourself. While this is fine for queries that return small result-sets, it can grow unmanageable in cases of huge result-sets.

The query must be totally received before this timeout, which defaults to 30 seconds. Implementation depend of server type and version.Comment 2. The first two patterns we looked at in this series were Node. While effective, those patterns are not the only ways of writing asynchronous code.

Promises are important to learn because many modules use them in their APIs. This post will cover the basics of promises and demonstrate how they can be used to construct asynchronous applications.

Promise instances have two important properties: state and value. When the resolver function is executed, which happens immediately when creating new instances, these parameters will be functions that can transition the state of the promise and provide a value.

Promises are typically resolved when the resolver completes successfully and rejected if an error occurs. If you run the above script in either a browser or Node. For now, ignore any errors related to uncaught or unhandled promise rejections more on that later. Note that this demo script is completely synchronous.

Once a promise has been resolved or rejected, its state and value become immutable. Both methods accept callback functions that may be invoked asynchronously at some point in the future. To demonstrate how error handling works, some random numbers will throw exceptions. If you run the script above several times, you should see success messages and the occasional error message. Did you notice how the catch call flows off the then call?

That technique is called promise chaining. Becuase these promises are not created with the constructor function, they are not resolved or rejected with a resolver function.

If an error is thrown and goes unhandled, then the promise will be rejected and the error will be passed to the next error handler in the chain. If you run the above script with Node. As you can see, errors thrown and values returned are routed to the next appropriate handler in the chain. Things get more interesting when the value returned is a promise. When this happens, the next handler in the chain will not be invoked until that promise is resolved or rejected.

With a little luck, when you run the script, you should see three random values printed to the console every two seconds. As you can see, promise chaining is a great way to run async operations in series without running into callback hell. But what about more complex flows?

nodejs mysql promise

In this section, I want to explain something that often trips up folks that are new to promises. This means the error will be passed to the next error handler in the chain.Since Node. As Node. In this article, I will briefly show you what async functions are, and how they change the way we write Node.

When the async function is called, it returns with a Promise. When the async function returns a value, the Promise gets fulfilled, if the async function throws an error, it gets rejected. The await keyword can be used to wait for a Promise to be resolved and returns the fulfilled value. If the value passed to the await keyword is not a Promise, it converts the value to a resolved Promise.

If your Node. If your applications are built using callbacks, moving to async functions should be done gradually. You can start adding new features by using this new technique. If you have to use older parts of the application, you can simply wrap them into Promises.

As express supports Promises out of the box, using async functions with express is as simple as:. Edit 1: as Keith Smith pointed out, the above example has a serious issue - if the Promise gets rejected, the express route handler would just hang because there was no error handling there. Imagine you are working on something similar, when an operation needs two inputs, one from a database, and one from an external service:. As you can see, you can do the first two in parallel, as they have no dependency on each other.

For this, you should use the Promise. In some cases, you only need the result of the fastest resolving Promise - in that cases, you can use the Promise. In the newer versions of Node. Because of this, you should use try-catch blocks, when necessary:. However, with try-catch blocks you can hide important exceptions, like system errors, which you want to rethrow.

Use MySQL in Node.js

One of the first async control flow libraries for Node. It provides asynchronous helpers, like:. If you do not want to reinvent the wheel and implement the same logic again, and you also want to depend on a battle-tested library downloaded 50 million times a month, you can simply reuse these functions with async functions as well, using the util. I hope you enjoyed this article and learned a lot!

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nodejs mysql promise

Follow me nthgergo! What are async functions? To do so, you can use the built-in util. PORT Edit 1: as Keith Smith pointed out, the above example has a serious issue - if the Promise gets rejected, the express route handler would just hang because there was no error handling there.GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together.

If nothing happens, download GitHub Desktop and try again. If nothing happens, download Xcode and try again. If nothing happens, download the GitHub extension for Visual Studio and try again. This function must either return the wrapped mysql object, return a promise of the wrapped mysql object or call the callback that is passed into the function.

The main difference is that mysql. Besides this, the API is the same and you should be able to upgrade straight to v4. The only other difference is the extra options in the connectionOptions object. Skip to content. Dismiss Join GitHub today GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together. Sign up. No description, website, or topics provided.

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JavaScript Branch: master. Find file. Sign in Sign up. Go back. Launching Xcode If nothing happens, download Xcode and try again. Latest commit. CodeFoodPixels 4. Latest commit f4f9e3f Feb 4, API mysql. Parameters connectionOptions object : A connectionOptions object Return value A Bluebird Promise that resolves to a connection object mysql. Function arguments mysql mysql object : The mysql object callback error, success function : A node-style callback that can be used to pass the wrapped version of the mysql object out of the wrapper function.

Connection object methods connection. Pool object methods pool. Upgrading from v3 The main difference is that mysql. You signed in with another tab or window. Reload to refresh your session. You signed out in another tab or window. Add connection examples.


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