PostgreSQL client - pure javascript & libpq with the same API
node-postgres
Non-blocking PostgreSQL client for node.js. Pure JavaScript and optional native libpq bindings.
Install
$ npm install pg
Intro & Examples
There are 3 ways of executing queries
- Passing the query to a pool
- Borrowing a client from a pool and executing the query with it
- Obtaining an exclusive client and executing the query with it
It is recommended to pass the query to a pool as often as possible. If that isn't possible, because of long and complex transactions for example, borrow a client from a pool. Just remember to initialize the pool only once in your code so you maximize reusability of connections.
Why pooling?
If you're working on something like a web application which makes frequent queries you'll want to access the PostgreSQL server through a pool of clients. Why? For one thing, there is ~20-30 millisecond delay (YMMV) when connecting a new client to the PostgreSQL server because of the startup handshake. Furthermore, PostgreSQL can support only a limited number of clients...it depends on the amount of ram on your database server, but generally more than 100 clients at a time is a very bad thing. :tm: Additionally, PostgreSQL can only execute 1 query at a time per connected client, so pipelining all queries for all requests through a single, long-lived client will likely introduce a bottleneck into your application if you need high concurrency.
With that in mind we can imagine a situation where you have a web server which connects and disconnects a new client for every web request or every query (don't do this!). If you get only 1 request at a time everything will seem to work fine, though it will be a touch slower due to the connection overhead. Once you get >100 simultaneous requests your web server will attempt to open 100 connections to the PostgreSQL backend and :boom: you'll run out of memory on the PostgreSQL server, your database will become unresponsive, your app will seem to hang, and everything will break. Boooo!
Good news: node-postgres ships with built in client pooling. Client pooling allows your application to use a pool of already connected clients and reuse them for each request to your application. If your app needs to make more queries than there are available clients in the pool the queries will queue instead of overwhelming your database & causing a cascading failure. :thumbsup:
node-postgres uses pg-pool to manage pooling. It bundles it and exports it for convenience. If you want, you can require('pg-pool') and use it directly - it's the same as the constructor exported at pg.Pool.
It's highly recommended you read the documentation for pg-pool.
Here is an up & running quickly example
For more information about config.ssl check TLS (SSL) of nodejs
Pooling example
Let's create a pool in ./lib/db.js which will be reused across the whole project
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Now if in ./foo.js you want to pass a query to the pool
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---For more examples, including how to use a connection pool with promises and async/await see the example page in the wiki.
Obtaining an exclusive client, example
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More Documentation
Native Bindings
To install the native bindings:
$ npm install pg pg-native
node-postgres contains a pure JavaScript protocol implementation which is quite fast, but you can optionally use native bindings for a 20-30% increase in parsing speed (YMMV). Both versions are adequate for production workloads. I personally use the pure JavaScript implementation because I like knowing what's going on all the way down to the binary on the socket, and it allows for some fancier use cases which are difficult to do with libpq. :smile:
To use the native bindings, first install pg-native. Once pg-native is installed, simply replace var pg = require('pg') with var pg = require('pg').native. Make sure any exported constructors from pg are from the native instance. Example:
var pg = require('pg').native
var Pool = require('pg').Pool // bad! this is not bound to the native client
var Client = require('pg').Client // bad! this is the pure JavaScript client
var pg = require('pg').native
var Pool = pg.Pool // good! a pool bound to the native client
var Client = pg.Client // good! this client uses libpq bindingsAPI differences
node-postgres abstracts over the pg-native module to provide the same interface as the pure JavaScript version. Care has been taken to keep the number of api differences between the two modules to a minimum.
However, currently some differences remain, especially :
- the error object in pg-native is different : notably, the information about the postgres error code is not present in field
codebut in the fieldsqlState, and the name of a few other fields is different (see https://github.com/brianc/node-postgres/issues/938, https://github.com/brianc/node-postgres/issues/972). So for example, if you rely on error.code in your application, your will have to adapt your code to work with native bindings. - the notification object has a few less properties (see https://github.com/brianc/node-postgres/issues/1045)
- column objects have less properties (see https://github.com/brianc/node-postgres/issues/988)
- the modules https://github.com/brianc/node-pg-copy-streams and https://github.com/brianc/node-pg-query-stream do not work with native bindings (you will have to require 'pg' to use them).
Thus, it is recommended you use either the pure JavaScript or native bindings in both development and production and don't mix & match them in the same process - it can get confusing!
Features
- pure JavaScript client and native libpq bindings share the same api
- connection pooling
- extensible js<->postgresql data-type coercion
- supported PostgreSQL features
- parameterized queries
- named statements with query plan caching
- async notifications with
LISTEN/NOTIFY - bulk import & export with
COPY TO/COPY FROM
Extras
node-postgres is by design pretty light on abstractions. These are some handy modules we've been using over the years to complete the picture. Entire list can be found on wiki
Contributing
:heart: contributions!
If you need help getting the tests running locally or have any questions about the code when working on a patch please feel free to email me or gchat me.
I will happily accept your pull request if it:
- has tests
- looks reasonable
- does not break backwards compatibility
Information about the testing processes is in the wiki.
Open source belongs to all of us, and we're all invited to participate!
Troubleshooting and FAQ
The causes and solutions to common errors can be found among the Frequently Asked Questions(FAQ)
Support
If at all possible when you open an issue please provide
- version of node
- version of postgres
- smallest possible snippet of code to reproduce the problem
Usually I'll pop the code into the repo as a test. Hopefully the test fails. Then I make the test pass. Then everyone's happy!
If you need help or run into any issues getting node-postgres to work on your system please report a bug or contact me directly. I am usually available via google-talk at my github account public email address. Remember this is a labor of love, and though I try to get back to everything sometimes life takes priority, and I might take a while. It helps if you use nice code formatting in your issue, search for existing answers before posting, and come back and close out the issue if you figure out a solution. The easier you can make it for me, the quicker I'll try and respond to you!
If you need deeper support, have application specific questions, would like to sponsor development, or want consulting around node & postgres please send me an email, I'm always happy to discuss!
I usually tweet about any important status updates or changes to node-postgres on twitter. Follow me @briancarlson to keep up to date.
License
Copyright (c) 2010-2017 Brian Carlson (brian.m.carlson@gmail.com)
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
HomePage
http://github.com/brianc/node-postgres
Repository
git://github.com/brianc/node-postgres.git
来源：JavaScript中文网 ，转载请注明来源 https://www.javascriptcn.com/post/6005606981e8991b448de8cf