1578448677
Install
source-shell
$ npm install postgres
Use
source-js
const postgres = require('postgres')
const sql = postgres({ ...options }) // will default to the same as psql
await sql`
select name, age from users
`
// > [{ name: 'Murray', age: 68 }, { name: 'Walter', age 78 }]
postgres([url], [options])
You can use either a postgres://
url connection string or the options to define your database connection properties. Options in the object will override any present in the url.
source-js
const sql = postgres('postgres://username:password@host:port/database', {
host : '', // Postgres ip address or domain name
port : 5432, // Postgres server port
path : '', // unix socket path (usually '/tmp')
database : '', // Name of database to connect to
username : '', // Username of database user
password : '', // Password of database user
ssl : false, // True, or options for tls.connect
max : 10, // Max number of connections
timeout : 0, // Idle connection timeout in seconds
types : [], // Array of custom types, see more below
onnotice : fn // Defaults to console.log
onparameter : fn // (key, value) when server param change
debug : fn // Is called with (connection, query, parameters)
transform : {
column : fn, // Transforms incoming column names
value : fn, // Transforms incoming row values
row : fn // Transforms entire rows
},
connection : {
application_name : 'postgres.js', // Default application_name
... // Other connection parameters
}
})
More info for the ssl
option can be found in the Node.js docs for tls connect options
sql
-> Promise
A query will always return a Promise
which resolves to either an array [...]
or null
depending on the type of query. Destructuring is great to immidiately access the first element.
source-js
const [new_user] = await sql`
insert into users (
name, age
) values (
'Murray', 68
)
returning *
`
// new_user = { user_id: 1, name: 'Murray', age: 68 }
Parameters are automatically inferred and handled by Postgres so that SQL injection isn’t possible. No special handling is necessarry, simply use JS tagged template literals as usual.
source-js
let search = 'Mur'
const users = await sql`
select
name,
age
from users
where
name like ${ search + '%' }
`
// users = [{ name: 'Murray', age: 68 }]
sql
.stream(fn) -> Promise
If you want to handle rows returned by a query one by one you can use .stream
which returns a promise that resolves once there are no more rows.
source-js
await sql`
select created_at, name from events
`.stream(row => {
// row = { created_at: '2019-11-22T14:22:00Z', name: 'connected' }
})
// No more rows
When you call listen, a dedicated connection will automatically be made to ensure that you receive notifications in realtime. This connection will be used for any further calls to listen.
source-js
sql.listen('news', payload => {
const json = JSON.parse(payload)
console.log(json.this) // logs 'is'
})
Notify can be done as usual in sql, or by using the sql.notify
method.
sql.notify('news', JSON.stringify({ no: 'this', is: 'news' }))
sql() inside tagged template
Postgres.js has a safe, ergonomic way to aid you in writing queries. This makes it easier to write dynamic inserts, selects, updates and where queries.
source-js
const user = {
name: 'Murray',
age: 68
}
sql`
insert into users ${
sql(user)
}
`
Is translated into a safe query like this:
source-sql
insert into users (name, age) values ($1, $2)
If you need to insert multiple rows at the same time it’s also much faster to do it with a single insert
. Simply pass an array of objects to sql()
.
source-js
const users = [{
name: 'Murray',
age: 68,
garbage: 'ignore'
}, {
name: 'Walter',
age: 78
}]
sql`
insert into users ${
sql(users, 'name', 'age')
}
`
sql.array(Array)
Postgres has a native array type which is similar to js arrays, but Postgres only allows the same type and shape for nested items. This method automatically infers the item type and translates js arrays into Postgres arrays.
source-js
const types = sql`
insert into types (
integers,
strings,
dates,
buffers,
multi
) values (
${ sql.array([1,2,3,4,5]) },
${ sql.array(['Hello', 'Postgres']) },
${ sql.array([new Date(), new Date(), new Date()]) },
${ sql.array([Buffer.from('Hello'), Buffer.from('Postgres')]) },
${ sql.array([[[1,2],[3,4]][[5,6],[7,8]]]) },
)
`
sql.json(object)
source-js
const body = { hello: 'postgres' }
const [{ json }] = await sql`
insert into json (
body
) values (
${ sql.json(body) }
)
returning body
`
// json = { hello: 'postgres' }
sql.file(path, [args], [options]) -> Promise
Using an sql
file for a query. The contents will be cached in memory so that the file is only read once.
source-js
sql.file(path.join(__dirname, 'query.sql'), [], {
cache: true // Default true - disable for single shot queries or memory reasons
})
sql.begin(fn) -> Promise
Calling begin with a function will return a Promise which resolves with the returned value from the function. The function provides a single argument which is sql
with a context of the newly created transaction. BEGIN
is automatically called, and if the Promise fails ROLLBACK
will be called. If it succeeds COMMIT
will be called.
source-js
const [user, account] = await sql.begin(async sql => {
const [user] = await sql`
insert into users (
name
) values (
'Alice'
)
`
const [account] = await sql`
insert into accounts (
user_id
) values (
${ user.user_id }
)
`
return [user, account]
})
sql.savepoint([name], fn) -> Promise
source-js
sql.begin(async sql => {
const [user] = await sql`
insert into users (
name
) values (
'Alice'
)
`
const [account] = (await sql.savepoint(sql =>
sql`
insert into accounts (
user_id
) values (
${ user.user_id }
)
`
).catch(err => {
// Account could not be created. ROLLBACK SAVEPOINT is called because we caught the rejection.
})) || []
return [user, account]
})
.then(([user, account])) => {
// great success - COMMIT succeeded
})
.catch(() => {
// not so good - ROLLBACK was called
})
Do note that you can often achieve the same result using WITH
queries (Common Table Expressions) instead of using transactions.
You can add ergonomic support for custom types, or simply pass an object with a { type, value }
signature that contains the Postgres oid
for the type and the correctly serialized value.
Adding Query helpers is the recommended approach which can be done like this:
source-js
const sql = sql({
types: {
rect: {
to : 1337,
from : [1337],
serialize : ({ x, y, width, height }) => [x, y, width, height],
parse : ([x, y, width, height]) => { x, y, width, height }
}
}
})
const [custom] = sql`
insert into rectangles (
name,
rect
) values (
'wat',
${ sql.types.rect({ x: 13, y: 37: width: 42, height: 80 }) }
)
returning *
`
// custom = { name: 'wat', rect: { x: 13, y: 37: width: 42, height: 80 } }
To ensure proper teardown and cleanup on server restarts use sql.end({ timeout: null })
before process.exit()
Calling sql.end()
will reject new queries and return a Promise which resolves when all queries are finished and the underlying connections are closed. If a timeout is provided any pending queries will be rejected once the timeout is reached and the connections will be destroyed.
source-js
import prexit from 'prexit'
prexit(async () => {
await sql.end({ timeout: 5 })
await new Promise(r => server.close(r))
})
sql.unsafe(query, [args], [options]) -> promise
If you know what you’re doing, you can use unsafe
to pass any string you’d like to postgres. Please note that this can lead to sql injection if you’re not careful.
source-js
sql.unsafe('select ' + danger + ' from users where id = ' + dragons)
Errors are all thrown to related queries and never globally. Errors comming from Postgres itself are always in the native Postgres format, and the same goes for any Node.js errors eg. coming from the underlying connection.
There are also the following errors specifically for this library.
X (X) is not supported
Whenever a message is received from Postgres which is not supported by this library. Feel free to file an issue if you think something is missing.
Max number of parameters (65534) exceeded
The postgres protocol doesn’t allow more than 65534 (16bit) parameters. If you run into this issue there are various workarounds such as using sql([...])
to escape values instead of passing them as parameters.
Message type X not supported
When using SASL authentication the server responds with a signature at the end of the authentication flow which needs to match the one on the client. This is to avoid man in the middle attacks. If you receive this error the connection was canceled because the server did not reply with the expected signature.
Query not called as a tagged template literal
Making queries has to be done using the sql function as a tagged template. This is to ensure parameters are serialized and passed to Postgres as query parameters with correct types and to avoid SQL injection.
Auth type X not implemented
Postgres supports many different authentication types. This one is not supported.
write CONNECTION_CLOSED host:port
This error is thrown if the connection was closed without an error. This should not happen during normal operation, so please create an issue if this was unexpected.
write CONNECTION_ENDED host:port
This error is thrown if the user has called sql.end()
and performed a query afterwards.
write CONNECTION_DESTROYED host:port
This error is thrown for any queries that were pending when the timeout to sql.end({ timeout: X })
was reached.
#node-js #postgres #databaese #web-development #postgresql
1632537859
Not babashka. Node.js babashka!?
Ad-hoc CLJS scripting on Node.js.
Experimental. Please report issues here.
Nbb's main goal is to make it easy to get started with ad hoc CLJS scripting on Node.js.
Additional goals and features are:
Nbb requires Node.js v12 or newer.
CLJS code is evaluated through SCI, the same interpreter that powers babashka. Because SCI works with advanced compilation, the bundle size, especially when combined with other dependencies, is smaller than what you get with self-hosted CLJS. That makes startup faster. The trade-off is that execution is less performant and that only a subset of CLJS is available (e.g. no deftype, yet).
Install nbb
from NPM:
$ npm install nbb -g
Omit -g
for a local install.
Try out an expression:
$ nbb -e '(+ 1 2 3)'
6
And then install some other NPM libraries to use in the script. E.g.:
$ npm install csv-parse shelljs zx
Create a script which uses the NPM libraries:
(ns script
(:require ["csv-parse/lib/sync$default" :as csv-parse]
["fs" :as fs]
["path" :as path]
["shelljs$default" :as sh]
["term-size$default" :as term-size]
["zx$default" :as zx]
["zx$fs" :as zxfs]
[nbb.core :refer [*file*]]))
(prn (path/resolve "."))
(prn (term-size))
(println (count (str (fs/readFileSync *file*))))
(prn (sh/ls "."))
(prn (csv-parse "foo,bar"))
(prn (zxfs/existsSync *file*))
(zx/$ #js ["ls"])
Call the script:
$ nbb script.cljs
"/private/tmp/test-script"
#js {:columns 216, :rows 47}
510
#js ["node_modules" "package-lock.json" "package.json" "script.cljs"]
#js [#js ["foo" "bar"]]
true
$ ls
node_modules
package-lock.json
package.json
script.cljs
Nbb has first class support for macros: you can define them right inside your .cljs
file, like you are used to from JVM Clojure. Consider the plet
macro to make working with promises more palatable:
(defmacro plet
[bindings & body]
(let [binding-pairs (reverse (partition 2 bindings))
body (cons 'do body)]
(reduce (fn [body [sym expr]]
(let [expr (list '.resolve 'js/Promise expr)]
(list '.then expr (list 'clojure.core/fn (vector sym)
body))))
body
binding-pairs)))
Using this macro we can look async code more like sync code. Consider this puppeteer example:
(-> (.launch puppeteer)
(.then (fn [browser]
(-> (.newPage browser)
(.then (fn [page]
(-> (.goto page "https://clojure.org")
(.then #(.screenshot page #js{:path "screenshot.png"}))
(.catch #(js/console.log %))
(.then #(.close browser)))))))))
Using plet
this becomes:
(plet [browser (.launch puppeteer)
page (.newPage browser)
_ (.goto page "https://clojure.org")
_ (-> (.screenshot page #js{:path "screenshot.png"})
(.catch #(js/console.log %)))]
(.close browser))
See the puppeteer example for the full code.
Since v0.0.36, nbb includes promesa which is a library to deal with promises. The above plet
macro is similar to promesa.core/let
.
$ time nbb -e '(+ 1 2 3)'
6
nbb -e '(+ 1 2 3)' 0.17s user 0.02s system 109% cpu 0.168 total
The baseline startup time for a script is about 170ms seconds on my laptop. When invoked via npx
this adds another 300ms or so, so for faster startup, either use a globally installed nbb
or use $(npm bin)/nbb script.cljs
to bypass npx
.
Nbb does not depend on any NPM dependencies. All NPM libraries loaded by a script are resolved relative to that script. When using the Reagent module, React is resolved in the same way as any other NPM library.
To load .cljs
files from local paths or dependencies, you can use the --classpath
argument. The current dir is added to the classpath automatically. So if there is a file foo/bar.cljs
relative to your current dir, then you can load it via (:require [foo.bar :as fb])
. Note that nbb
uses the same naming conventions for namespaces and directories as other Clojure tools: foo-bar
in the namespace name becomes foo_bar
in the directory name.
To load dependencies from the Clojure ecosystem, you can use the Clojure CLI or babashka to download them and produce a classpath:
$ classpath="$(clojure -A:nbb -Spath -Sdeps '{:aliases {:nbb {:replace-deps {com.github.seancorfield/honeysql {:git/tag "v2.0.0-rc5" :git/sha "01c3a55"}}}}}')"
and then feed it to the --classpath
argument:
$ nbb --classpath "$classpath" -e "(require '[honey.sql :as sql]) (sql/format {:select :foo :from :bar :where [:= :baz 2]})"
["SELECT foo FROM bar WHERE baz = ?" 2]
Currently nbb
only reads from directories, not jar files, so you are encouraged to use git libs. Support for .jar
files will be added later.
The name of the file that is currently being executed is available via nbb.core/*file*
or on the metadata of vars:
(ns foo
(:require [nbb.core :refer [*file*]]))
(prn *file*) ;; "/private/tmp/foo.cljs"
(defn f [])
(prn (:file (meta #'f))) ;; "/private/tmp/foo.cljs"
Nbb includes reagent.core
which will be lazily loaded when required. You can use this together with ink to create a TUI application:
$ npm install ink
ink-demo.cljs
:
(ns ink-demo
(:require ["ink" :refer [render Text]]
[reagent.core :as r]))
(defonce state (r/atom 0))
(doseq [n (range 1 11)]
(js/setTimeout #(swap! state inc) (* n 500)))
(defn hello []
[:> Text {:color "green"} "Hello, world! " @state])
(render (r/as-element [hello]))
Working with callbacks and promises can become tedious. Since nbb v0.0.36 the promesa.core
namespace is included with the let
and do!
macros. An example:
(ns prom
(:require [promesa.core :as p]))
(defn sleep [ms]
(js/Promise.
(fn [resolve _]
(js/setTimeout resolve ms))))
(defn do-stuff
[]
(p/do!
(println "Doing stuff which takes a while")
(sleep 1000)
1))
(p/let [a (do-stuff)
b (inc a)
c (do-stuff)
d (+ b c)]
(prn d))
$ nbb prom.cljs
Doing stuff which takes a while
Doing stuff which takes a while
3
Also see API docs.
Since nbb v0.0.75 applied-science/js-interop is available:
(ns example
(:require [applied-science.js-interop :as j]))
(def o (j/lit {:a 1 :b 2 :c {:d 1}}))
(prn (j/select-keys o [:a :b])) ;; #js {:a 1, :b 2}
(prn (j/get-in o [:c :d])) ;; 1
Most of this library is supported in nbb, except the following:
:syms
.-x
notation. In nbb, you must use keywords.See the example of what is currently supported.
See the examples directory for small examples.
Also check out these projects built with nbb:
See API documentation.
See this gist on how to convert an nbb script or project to shadow-cljs.
Prequisites:
To build:
bb release
Run bb tasks
for more project-related tasks.
Download Details:
Author: borkdude
Download Link: Download The Source Code
Official Website: https://github.com/borkdude/nbb
License: EPL-1.0
#node #javascript
1616671994
If you look at the backend technology used by today’s most popular apps there is one thing you would find common among them and that is the use of NodeJS Framework. Yes, the NodeJS framework is that effective and successful.
If you wish to have a strong backend for efficient app performance then have NodeJS at the backend.
WebClues Infotech offers different levels of experienced and expert professionals for your app development needs. So hire a dedicated NodeJS developer from WebClues Infotech with your experience requirement and expertise.
So what are you waiting for? Get your app developed with strong performance parameters from WebClues Infotech
For inquiry click here: https://www.webcluesinfotech.com/hire-nodejs-developer/
Book Free Interview: https://bit.ly/3dDShFg
#hire dedicated node.js developers #hire node.js developers #hire top dedicated node.js developers #hire node.js developers in usa & india #hire node js development company #hire the best node.js developers & programmers
1622719015
Front-end web development has been overwhelmed by JavaScript highlights for quite a long time. Google, Facebook, Wikipedia, and most of all online pages use JS for customer side activities. As of late, it additionally made a shift to cross-platform mobile development as a main technology in React Native, Nativescript, Apache Cordova, and other crossover devices.
Throughout the most recent couple of years, Node.js moved to backend development as well. Designers need to utilize a similar tech stack for the whole web project without learning another language for server-side development. Node.js is a device that adjusts JS usefulness and syntax to the backend.
Node.js isn’t a language, or library, or system. It’s a runtime situation: commonly JavaScript needs a program to work, however Node.js makes appropriate settings for JS to run outside of the program. It’s based on a JavaScript V8 motor that can run in Chrome, different programs, or independently.
The extent of V8 is to change JS program situated code into machine code — so JS turns into a broadly useful language and can be perceived by servers. This is one of the advantages of utilizing Node.js in web application development: it expands the usefulness of JavaScript, permitting designers to coordinate the language with APIs, different languages, and outside libraries.
Of late, organizations have been effectively changing from their backend tech stacks to Node.js. LinkedIn picked Node.js over Ruby on Rails since it took care of expanding responsibility better and decreased the quantity of servers by multiple times. PayPal and Netflix did something comparative, just they had a goal to change their design to microservices. We should investigate the motivations to pick Node.JS for web application development and when we are planning to hire node js developers.
The principal thing that makes Node.js a go-to environment for web development is its JavaScript legacy. It’s the most well known language right now with a great many free devices and a functioning local area. Node.js, because of its association with JS, immediately rose in ubiquity — presently it has in excess of 368 million downloads and a great many free tools in the bundle module.
Alongside prevalence, Node.js additionally acquired the fundamental JS benefits:
In addition, it’s a piece of a well known MEAN tech stack (the blend of MongoDB, Express.js, Angular, and Node.js — four tools that handle all vital parts of web application development).
This is perhaps the most clear advantage of Node.js web application development. JavaScript is an unquestionable requirement for web development. Regardless of whether you construct a multi-page or single-page application, you need to know JS well. On the off chance that you are now OK with JavaScript, learning Node.js won’t be an issue. Grammar, fundamental usefulness, primary standards — every one of these things are comparable.
In the event that you have JS designers in your group, it will be simpler for them to learn JS-based Node than a totally new dialect. What’s more, the front-end and back-end codebase will be basically the same, simple to peruse, and keep up — in light of the fact that they are both JS-based.
There’s another motivation behind why Node.js got famous so rapidly. The environment suits well the idea of microservice development (spilling stone monument usefulness into handfuls or many more modest administrations).
Microservices need to speak with one another rapidly — and Node.js is probably the quickest device in information handling. Among the fundamental Node.js benefits for programming development are its non-obstructing algorithms.
Node.js measures a few demands all at once without trusting that the first will be concluded. Many microservices can send messages to one another, and they will be gotten and addressed all the while.
Node.js was worked in view of adaptability — its name really says it. The environment permits numerous hubs to run all the while and speak with one another. Here’s the reason Node.js adaptability is better than other web backend development arrangements.
Node.js has a module that is liable for load adjusting for each running CPU center. This is one of numerous Node.js module benefits: you can run various hubs all at once, and the environment will naturally adjust the responsibility.
Node.js permits even apportioning: you can part your application into various situations. You show various forms of the application to different clients, in light of their age, interests, area, language, and so on. This builds personalization and diminishes responsibility. Hub accomplishes this with kid measures — tasks that rapidly speak with one another and share a similar root.
What’s more, Node’s non-hindering solicitation handling framework adds to fast, letting applications measure a great many solicitations.
Numerous designers consider nonconcurrent to be one of the two impediments and benefits of Node.js web application development. In Node, at whatever point the capacity is executed, the code consequently sends a callback. As the quantity of capacities develops, so does the number of callbacks — and you end up in a circumstance known as the callback damnation.
In any case, Node.js offers an exit plan. You can utilize systems that will plan capacities and sort through callbacks. Systems will associate comparable capacities consequently — so you can track down an essential component via search or in an envelope. At that point, there’s no compelling reason to look through callbacks.
So, these are some of the top benefits of Nodejs in web application development. This is how Nodejs is contributing a lot to the field of web application development.
I hope now you are totally aware of the whole process of how Nodejs is really important for your web project. If you are looking to hire a node js development company in India then I would suggest that you take a little consultancy too whenever you call.
Good Luck!
#node.js development company in india #node js development company #hire node js developers #hire node.js developers in india #node.js development services #node.js development
1578448677
Install
source-shell
$ npm install postgres
Use
source-js
const postgres = require('postgres')
const sql = postgres({ ...options }) // will default to the same as psql
await sql`
select name, age from users
`
// > [{ name: 'Murray', age: 68 }, { name: 'Walter', age 78 }]
postgres([url], [options])
You can use either a postgres://
url connection string or the options to define your database connection properties. Options in the object will override any present in the url.
source-js
const sql = postgres('postgres://username:password@host:port/database', {
host : '', // Postgres ip address or domain name
port : 5432, // Postgres server port
path : '', // unix socket path (usually '/tmp')
database : '', // Name of database to connect to
username : '', // Username of database user
password : '', // Password of database user
ssl : false, // True, or options for tls.connect
max : 10, // Max number of connections
timeout : 0, // Idle connection timeout in seconds
types : [], // Array of custom types, see more below
onnotice : fn // Defaults to console.log
onparameter : fn // (key, value) when server param change
debug : fn // Is called with (connection, query, parameters)
transform : {
column : fn, // Transforms incoming column names
value : fn, // Transforms incoming row values
row : fn // Transforms entire rows
},
connection : {
application_name : 'postgres.js', // Default application_name
... // Other connection parameters
}
})
More info for the ssl
option can be found in the Node.js docs for tls connect options
sql
-> Promise
A query will always return a Promise
which resolves to either an array [...]
or null
depending on the type of query. Destructuring is great to immidiately access the first element.
source-js
const [new_user] = await sql`
insert into users (
name, age
) values (
'Murray', 68
)
returning *
`
// new_user = { user_id: 1, name: 'Murray', age: 68 }
Parameters are automatically inferred and handled by Postgres so that SQL injection isn’t possible. No special handling is necessarry, simply use JS tagged template literals as usual.
source-js
let search = 'Mur'
const users = await sql`
select
name,
age
from users
where
name like ${ search + '%' }
`
// users = [{ name: 'Murray', age: 68 }]
sql
.stream(fn) -> Promise
If you want to handle rows returned by a query one by one you can use .stream
which returns a promise that resolves once there are no more rows.
source-js
await sql`
select created_at, name from events
`.stream(row => {
// row = { created_at: '2019-11-22T14:22:00Z', name: 'connected' }
})
// No more rows
When you call listen, a dedicated connection will automatically be made to ensure that you receive notifications in realtime. This connection will be used for any further calls to listen.
source-js
sql.listen('news', payload => {
const json = JSON.parse(payload)
console.log(json.this) // logs 'is'
})
Notify can be done as usual in sql, or by using the sql.notify
method.
sql.notify('news', JSON.stringify({ no: 'this', is: 'news' }))
sql() inside tagged template
Postgres.js has a safe, ergonomic way to aid you in writing queries. This makes it easier to write dynamic inserts, selects, updates and where queries.
source-js
const user = {
name: 'Murray',
age: 68
}
sql`
insert into users ${
sql(user)
}
`
Is translated into a safe query like this:
source-sql
insert into users (name, age) values ($1, $2)
If you need to insert multiple rows at the same time it’s also much faster to do it with a single insert
. Simply pass an array of objects to sql()
.
source-js
const users = [{
name: 'Murray',
age: 68,
garbage: 'ignore'
}, {
name: 'Walter',
age: 78
}]
sql`
insert into users ${
sql(users, 'name', 'age')
}
`
sql.array(Array)
Postgres has a native array type which is similar to js arrays, but Postgres only allows the same type and shape for nested items. This method automatically infers the item type and translates js arrays into Postgres arrays.
source-js
const types = sql`
insert into types (
integers,
strings,
dates,
buffers,
multi
) values (
${ sql.array([1,2,3,4,5]) },
${ sql.array(['Hello', 'Postgres']) },
${ sql.array([new Date(), new Date(), new Date()]) },
${ sql.array([Buffer.from('Hello'), Buffer.from('Postgres')]) },
${ sql.array([[[1,2],[3,4]][[5,6],[7,8]]]) },
)
`
sql.json(object)
source-js
const body = { hello: 'postgres' }
const [{ json }] = await sql`
insert into json (
body
) values (
${ sql.json(body) }
)
returning body
`
// json = { hello: 'postgres' }
sql.file(path, [args], [options]) -> Promise
Using an sql
file for a query. The contents will be cached in memory so that the file is only read once.
source-js
sql.file(path.join(__dirname, 'query.sql'), [], {
cache: true // Default true - disable for single shot queries or memory reasons
})
sql.begin(fn) -> Promise
Calling begin with a function will return a Promise which resolves with the returned value from the function. The function provides a single argument which is sql
with a context of the newly created transaction. BEGIN
is automatically called, and if the Promise fails ROLLBACK
will be called. If it succeeds COMMIT
will be called.
source-js
const [user, account] = await sql.begin(async sql => {
const [user] = await sql`
insert into users (
name
) values (
'Alice'
)
`
const [account] = await sql`
insert into accounts (
user_id
) values (
${ user.user_id }
)
`
return [user, account]
})
sql.savepoint([name], fn) -> Promise
source-js
sql.begin(async sql => {
const [user] = await sql`
insert into users (
name
) values (
'Alice'
)
`
const [account] = (await sql.savepoint(sql =>
sql`
insert into accounts (
user_id
) values (
${ user.user_id }
)
`
).catch(err => {
// Account could not be created. ROLLBACK SAVEPOINT is called because we caught the rejection.
})) || []
return [user, account]
})
.then(([user, account])) => {
// great success - COMMIT succeeded
})
.catch(() => {
// not so good - ROLLBACK was called
})
Do note that you can often achieve the same result using WITH
queries (Common Table Expressions) instead of using transactions.
You can add ergonomic support for custom types, or simply pass an object with a { type, value }
signature that contains the Postgres oid
for the type and the correctly serialized value.
Adding Query helpers is the recommended approach which can be done like this:
source-js
const sql = sql({
types: {
rect: {
to : 1337,
from : [1337],
serialize : ({ x, y, width, height }) => [x, y, width, height],
parse : ([x, y, width, height]) => { x, y, width, height }
}
}
})
const [custom] = sql`
insert into rectangles (
name,
rect
) values (
'wat',
${ sql.types.rect({ x: 13, y: 37: width: 42, height: 80 }) }
)
returning *
`
// custom = { name: 'wat', rect: { x: 13, y: 37: width: 42, height: 80 } }
To ensure proper teardown and cleanup on server restarts use sql.end({ timeout: null })
before process.exit()
Calling sql.end()
will reject new queries and return a Promise which resolves when all queries are finished and the underlying connections are closed. If a timeout is provided any pending queries will be rejected once the timeout is reached and the connections will be destroyed.
source-js
import prexit from 'prexit'
prexit(async () => {
await sql.end({ timeout: 5 })
await new Promise(r => server.close(r))
})
sql.unsafe(query, [args], [options]) -> promise
If you know what you’re doing, you can use unsafe
to pass any string you’d like to postgres. Please note that this can lead to sql injection if you’re not careful.
source-js
sql.unsafe('select ' + danger + ' from users where id = ' + dragons)
Errors are all thrown to related queries and never globally. Errors comming from Postgres itself are always in the native Postgres format, and the same goes for any Node.js errors eg. coming from the underlying connection.
There are also the following errors specifically for this library.
X (X) is not supported
Whenever a message is received from Postgres which is not supported by this library. Feel free to file an issue if you think something is missing.
Max number of parameters (65534) exceeded
The postgres protocol doesn’t allow more than 65534 (16bit) parameters. If you run into this issue there are various workarounds such as using sql([...])
to escape values instead of passing them as parameters.
Message type X not supported
When using SASL authentication the server responds with a signature at the end of the authentication flow which needs to match the one on the client. This is to avoid man in the middle attacks. If you receive this error the connection was canceled because the server did not reply with the expected signature.
Query not called as a tagged template literal
Making queries has to be done using the sql function as a tagged template. This is to ensure parameters are serialized and passed to Postgres as query parameters with correct types and to avoid SQL injection.
Auth type X not implemented
Postgres supports many different authentication types. This one is not supported.
write CONNECTION_CLOSED host:port
This error is thrown if the connection was closed without an error. This should not happen during normal operation, so please create an issue if this was unexpected.
write CONNECTION_ENDED host:port
This error is thrown if the user has called sql.end()
and performed a query afterwards.
write CONNECTION_DESTROYED host:port
This error is thrown for any queries that were pending when the timeout to sql.end({ timeout: X })
was reached.
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