Non-blocking PostgreSQL client for Node.js written in TypeScript.
To install the latest version of this library:
$ npm install ts-postgres@latest- Fast!
- Supports both binary and text value formats
- Result data is currently sent in binary format only
- Multiple queries can be sent at once (pipeline)
- Extensible value model
- Hybrid query result object
- Iterable (synchronous or asynchronous; one row at a time)
- Promise-based
- Streaming
The client uses an async/await-based programming model.
import{Client}from'ts-postgres';asyncfunctionmain(){constclient=newClient();awaitclient.connect();try{// Querying the client returns a query result promise// which is also an asynchronous result iterator.constresult=client.query("SELECT 'Hello ' || $1 || '!' AS message",['world']);forawait(constrowofresult){// 'Hello world!'console.log(row.get('message'));}}finally{awaitclient.end();}}awaitmain()Waiting on the result (i.e., result iterator) returns the complete query result.
constresult=awaitclient.query(...)If the query fails, an exception is thrown.
The client constructor takes an optional Configuration object.
For example, to connect to a remote host use the host configuration key:
constclient=newClient({"host": <hostname>});The following table lists the various configuration options and their default value when applicable.
| Key | Type | Default |
|---|---|---|
| host | string | "localhost" |
| port | number | 5432 |
| user | string | The username of the process owner |
| database | string | "postgres" |
| password | string | |
| types | Map<DataType, ValueTypeReader> | Default value mapping for built-in types |
| extraFloatDigits | number | 0 |
| keepAlive | boolean | true |
| preparedStatementPrefix | string | "tsp_" |
The query method accepts a Query object or a number of arguments
that together define the query, the first argument (query text) being
the only required one.
The initial example above could be written as:
constquery=newQuery("SELECT 'Hello ' || $1 || '!' AS message",['world']);constresult=awaitclient.execute(query);Query parameters use the format $1, $2 etc.
When a specific data type is not inferrable from the query, PostgreSQL
uses DataType.Text as the default data type (which is mapped to the
string type in TypeScript). An explicit type can be provided in two
different ways:
Using type cast in the query, e.g.
$1::int.By passing a list of types to the query method:
import{DataType}from'ts-postgres';constresult=awaitclient.query("select $1 || ' bottles of beer'",[99],[DataType.Int4]);
Note that the number type in TypeScript has a maximum safe integer
value which lies between and DataType.Int8 – given by
Number.MAX_SAFE_INTEGER. To use DataType.Int8 the bigint type
should be used.
Whether we're operating on a stream or an already waited for result set, the iterator interface provides the most high-level row interface. This also applies when using the spread operator:
constrows=[...result];Each row provides direct access to values through its data attribute, but we can also get a value by name using the get(name) method.
for(constrowofrows){console.log('The number is: '+row.get('i'));// 1, 2, 3, ...}Note that values are polymorphic and need to be explicitly cast to a concrete type such as number or string.
This interface is available on the already waited for result object. It makes data available in the rows attribute as an array of arrays (of values).
for(constrowofresult.rows){console.log('The number is: '+row[0]);// 1, 2, 3, ...}This is the most efficient way to work with result data. Column names are available as the names attribute of a result.
A query can support streaming of one or more columns directly into an asynchronous stream such as a network socket, or a file.
Assuming that socket is a writable stream:
constquery=newQuery("SELECT some_bytea_column",{streams: {"some_bytea_column": socket}});constresult=awaitclient.execute(query);This can for example be used to reduce time to first byte and memory use.
The query command accepts a single query only. If you need to send multiple queries, just call the method multiple times. For example, to send an update command in a transaction:
client.query('begin');client.query('update ...');awaitclient.query('commit');The queries are sent back to back over the wire, but PostgreSQL still processes them one at a time, in the order they were sent (first in, first out).
You can prepare a query and subsequently execute it multiple times. This is also known as a "prepared statement".
conststatement=awaitclient.prepare(`SELECT 'Hello ' || $1 || '!' AS message`);forawait(constrowofstatement.execute(['world'])){console.log(row.get('message'));// 'Hello world!'}When the prepared statement is no longer needed, it should be closed to release the resource.
awaitstatement.close();Prepared statements can be used (executed) multiple times, even concurrently.
Queries with parameters are sent using the prepared statement variant of the extended query protocol. In this variant, the type of each parameter is determined prior to parameter binding, ensuring that values are encoded in the correct format.
If a query has no parameters, it uses the portal variant which saves a round trip.
The copy commands are not supported.
How do I set up a pool of connections? You can for example use the generic-pool library:
import{createPool}from'generic-pool';constpool=createPool({create: async()=>{constclient=newClient();returnclient.connect().then(()=>{client.on('error',console.log);returnclient;});},destroy: async(client: Client)=>{returnclient.end().then(()=>{})},validate: (client: Client)=>{returnPromise.resolve(!client.closed);}},{testOnBorrow: true});pool.use(...)
Use the following environment variable to run tests in "benchmark" mode.
$ NODE_ENV=benchmark npm run testts-postgres is free software. If you encounter a bug with the library please open an issue on the GitHub repo.
Copyright (c) 2018-2021 Malthe Borch (mborch@gmail.com)
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