pg-promise
===========
[Promises/A+] interface for PostgreSQL.
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---
* Supporting [Promise], [Bluebird], [When], [Q], etc.
* Transactions, functions, flexible query formatting;
* Automatic database connections;
* Strict query result filters.
---
* [About](#about)
* [Installing](#installing)
* [Getting Started](#getting-started)
- [Initialization](#initialization)
- [Database](#database)
- [Documentation](#documentation)
* [Testing](#testing)
* [Usage](#usage)
- [Queries and Parameters](#queries-and-parameters)
- [SQL Names](#sql-names)
- [Raw Text](#raw-text)
- [Open Values](#open-values)
- [Query Result Mask](#query-result-mask)
- [Named Parameters](#named-parameters)
- [Conversion Helpers](#conversion-helpers)
- [Custom Type Formatting](#custom-type-formatting)
- [Raw Custom Types](#raw-custom-types)
- [Query Files](#query-files)
- [Tasks](#tasks)
- [Transactions](#transactions)
- [Nested Transactions](#nested-transactions)
- [Synchronous Transactions](#synchronous-transactions)
- [Configurable Transactions](#configurable-transactions)
- [Generators](#generators)
* [Advanced](#advanced)
- [Initialization Options](#initialization-options)
- [Library de-initialization](#library-de-initialization)
* [History](#history)
* [License](#license)
---
# About
Built on top of [node-postgres] and its connection pool, this library translates their callback interface into one based on [Promises/A+],
while extending the protocol to a higher level, with automated connections and transactions management.
In addition, the library provides:
* its own, more flexible query formatting;
* event reporting for connectivity, errors, queries and transactions;
* support for all popular promise libraries + ES6 generators;
* declarative approach to controlling query results.
# Installing
```
$ npm install pg-promise
```
# Getting Started
## Initialization
Loading and initializing the library with [Initialization Options]:
```js
var pgp = require('pg-promise')({
// Initialization Options
});
```
− or without [Initialization Options]:
```js
var pgp = require('pg-promise')();
```
## Database
Create your [Database] object from the connection details:
```js
var db = pgp(connection);
```
The `connection` parameter can be any of the following:
* [Configuration Object]
* [Connection String]
Object `db` represents the [Database] protocol with lazy connection, i.e. only the actual query methods acquire
and release the connection. You should create only one global/shared `db` object per connection details.
## Documentation
* [Learn by Example] - the quickest way to get started with this library
* [Protocol API] - all the latest protocol documentation
* [Wiki Pages](https://github.com/vitaly-t/pg-promise/wiki) - all the documentation references
* [TypeScript](https://github.com/vitaly-t/pg-promise/tree/master/typescript) declarations for the library
# Testing
* Clone the repository (or download, if you prefer):
```
$ git clone https://github.com/vitaly-t/pg-promise
```
* Install the library's DEV dependencies:
```
$ npm install
```
* Make sure all tests can connect to your local test database, using the connection details in
[test/db/header.js](https://github.com/vitaly-t/pg-promise/blob/master/test/db/header.js).
Either set up your test database accordingly or change the connection details in that file.
* Initialize the database with some test data:
```
$ node test/db/init.js
```
* To run all tests:
```
$ npm test
```
* To run all tests with coverage:
```
$ npm run coverage
```
# Usage
## Queries and Parameters
Every connection context of the library shares the same query protocol, starting with generic method `query`,
defined as shown below:
```javascript
function query(query, values, qrm);
```
* `query` (required) - a string with support for three types of formatting, depending on the `values` passed:
- format `$1` (single variable), if `values` is of type `string`, `boolean`, `number`, `Date`, `function`, `null` or [QueryFile];
- format `$1, $2, etc..`, if `values` is an array;
- format `$*propName*`, if `values` is an object (not `null` and not `Date`), where `*` is any of the supported open-close pairs: `{}`, `()`, `<>`, `[]`, `//`;
* `values` (optional) - value/array/object to replace the variables in the query;
* `qrm` - (optional) *Query Result Mask*, as explained below. When not passed, it defaults to `pgp.queryResult.any`.
When a value/property inside array/object is an array, it is treated as a [PostgreSQL Array Type](http://www.postgresql.org/docs/9.4/static/arrays.html),
converted into the array constructor format of `array[]`, the same as calling method `pgp.as.array()`.
When a value/property inside array/object is of type `object` (except for `null`, `Date` or `Buffer`), it is automatically
serialized into JSON, the same as calling method `pgp.as.json()`, except the latter would convert anything to JSON.
For the latest SQL formatting support see method [as.format]
### SQL Names
When a variable ends with `~` (tilde) or `:name`, it represents an SQL name or identifier, which must be a text
string of at least 1 character long. Such name is then properly escaped and wrapped in double quotes.
```js
query('INSERT INTO $1~($2~) VALUES(...)', ['Table Name', 'Column Name']);
//=> INSERT INTO "Table Name"("Column Name") VALUES(...)
// A mixed example for a dynamic column list:
var columns = ['id', 'message'];
query('SELECT ${columns^} FROM ${table~}', {
columns: columns.map(pgp.as.name).join(),
table: 'Table Name'
});
//=> SELECT "id","message" FROM "Table Name"
```
Version 5.2.1 and later supports extended syntax for `${this~}` and for method [as.name]:
```js
var obj = {
one: 1,
two: 2
};
format("INSERT INTO table(${this~}) VALUES(${one}, ${two})", obj);
//=>INSERT INTO table("one","two") VALUES(1, 2)
```
Relying on this type of formatting for sql names and identifiers, along with regular variable formatting
makes your application impervious to sql injection.
See method [as.name] for the latest API.
### Raw Text
Raw-text values can be injected by ending the variable name with `^` or `:raw`:
`$1^, $2^, etc...`, `$*varName^*`, where `*` is any of the supported open-close pairs: `{}`, `()`, `<>`, `[]`, `//`
Raw text is injected without any pre-processing, which means:
* No proper escaping (replacing each single-quote symbol `'` with two);
* No wrapping text into single quotes.
Unlike regular variables, value for raw-text variables cannot be `null` or `undefined`, because of the ambiguous meaning
in this case. If such values are passed in, the formatter will throw error `Values null/undefined cannot be used as raw text.`
Special syntax `this^` within the [Named Parameters](#named-parameters) refers to the formatting object itself, to be injected
as a raw-text JSON-formatted string.
For the latest SQL formatting support see method [as.format]
### Open Values
Open values simplify concatenation of string values within a query, primarily for such special cases as `LIKE`/`ILIKE` filters.
Names for open-value variables end with either `:value` or symbol `#`, and it means that such a value is to be properly
formatted and escaped, but not to be wrapped in quotes when it is a text.
Similar to [raw-text](#raw-text) variables, open-value variables are also not allowed to be `null` or `undefined`, or they will throw
error `Open values cannot be null or undefined.` And the difference is that [raw-text](#raw-text) variables are not escaped, while
open-value variables are properly escaped.
Below is an example of formatting `LIKE` filter that ends with a second name:
```js
// using $1# or $1:value syntax:
query("...WHERE name LIKE '%$1#'", "O'Connor");
query("...WHERE name LIKE '%$1:value'", "O'Connor");
//=> ...WHERE name LIKE '%O''Connor'
// using ${propName#} or ${propName:value} syntax:
query("...WHERE name LIKE '%${filter#}'", {filter: "O'Connor"});
query("...WHERE name LIKE '%${filter:value}'", {filter: "O'Connor"});
//=> ...WHERE name LIKE '%O''Connor'
```
See also: method [as.value].
## Query Result Mask
In order to eliminate the chances of unexpected query results and thus make the code more robust,
method `query` uses parameter `qrm` (Query Result Mask):
```js
///////////////////////////////////////////////////////
// Query Result Mask flags;
//
// Any combination is supported, except for one + many.
var queryResult = {
/** Single row is expected. */
one: 1,
/** One or more rows expected. */
many: 2,
/** Expecting no rows. */
none: 4,
/** many|none - any result is expected. */
any: 6
};
```
In the following generic-query example we indicate that the call can return anything:
```javascript
db.query('select * from users');
```
which is equivalent to making one of the following calls:
```javascript
var qrm = pgp.queryResult;
db.query('select * from users', undefined, qrm.many | qrm.none);
db.query('select * from users', undefined, qrm.any);
db.manyOrNone('select * from users');
db.any('select * from users');
```
This usage pattern is facilitated through result-specific methods that can be used instead of the generic query:
```javascript
db.many(query, values); // expects one or more rows
db.one(query, values); // expects a single row
db.none(query, values); // expects no rows
db.any(query, values); // expects anything, same as `manyOrNone`
db.oneOrNone(query, values); // expects 1 or 0 rows
db.manyOrNone(query, values); // expects anything, same as `any`
```
There is however one specific method `result(query, values)` to bypass any result verification, and instead resolve
with the original [Result] object passed from the [PG] library.
You can also add your own methods and properties to this protocol via the [extend](#extend) event.
Each query function resolves its **data** according to the `qrm` that was used:
* `none` - **data** is `null`. If the query returns any kind of data, it is rejected.
* `one` - **data** is a single object. If the query returns no data or more than one row of data, it is rejected.
* `many` - **data** is an array of objects. If the query returns no rows, it is rejected.
* `one`|`none` - **data** is `null`, if no data was returned; or a single object, if one row was returned.
If the query returns more than one row of data, the query is rejected.
* `many`|`none` - **data** is an array of objects. When no rows are returned, **data** is an empty array.
If you try to specify `one`|`many` in the same query, such query will be rejected without executing it, telling you that such mask is invalid.
If `qrm` is not specified when calling generic `query` method, it is assumed to be `many`|`none` = `any`, i.e. any kind of data expected.
> This is all about writing robust code, when the client specifies what kind of data it is ready to handle on the declarative level,
leaving the burden of all extra checks to the library.
## Named Parameters
The library supports named parameters in query formatting, with the syntax of `$*propName*`, where `*` is any of the following open-close
pairs: `{}`, `()`, `<>`, `[]`, `//`
```js
db.query('select * from users where name=${name} and active=$/active/', {
name: 'John',
active: true
});
```
The same goes for all types of query methods as well as method [as.format], where `values` can also be an object whose properties can be
referred to by name from within the query.
A valid property name consists of any combination of letters, digits, underscores or `$`, and they are case-sensitive.
Leading and trailing spaces around property names are ignored.
It is important to know that while property values `null` and `undefined` are both formatted as `null`,
an error is thrown when the property doesn't exist at all (except for `partial` replacements - see below).
You can also use `partial` replacements within method [as.format], to ignore variables that do not exist in the formatting object.
#### `this` reference
Property `this` is a reference to the formatting object itself, so it can be inserted as a JSON-formatted string, alongside its properties.
* `${this}` - inserts the object itself as a JSON-formatted string;
* `${this^}` - inserts the object itself as a raw-text JSON-formatted string.
**example:**
```js
var doc = {
id: 123,
body: "some text"
};
db.none("INSERT INTO documents(id, doc) VALUES(${id}, ${this})", doc)
.then(function () {
// success;
})
.catch(function (error) {
// error;
});
```
which will execute:
```
INSERT INTO documents(id, doc) VALUES(123, '{"id":123,"body":"some text"}')
```
Version 3.2.1 and later allows syntax `:json` as an alternative to formatting the value as a JSON string.
**NOTE:** Technically, it is possible in javascript, though not recommended, for an object to contain a property
with name `this`. And in such cases the property's value will be used instead.
## Functions and Procedures
In PostgreSQL stored procedures are just functions that usually do not return anything.
Suppose we want to call function **findAudit** to find audit records by `user_id` and maximum timestamp.
We can make such call as shown below:
```js
db.func('findAudit', [123, new Date()])
.then(function (data) {
console.log(data); // printing the data returned
})
.catch(function (error) {
console.log(error); // printing the error
});
```
We passed it `user_id = 123`, plus current Date/Time as the timestamp. We assume that the function signature matches
the parameters that we passed. All values passed are serialized automatically to comply with PostgreSQL type formats.
Method `func` accepts optional third parameter - `qrm` (Query Result Mask), the same as method `query`.
And when you are not expecting any return results, call `db.proc` instead. Both methods return a [Promise] object,
but `db.proc` doesn't take a `qrm` parameter, always assuming it is `one`|`none`.
Summary for supporting procedures and functions:
* `func(query, values, qrm)` - expects the result according to `qrm`
* `proc(query, values)` - calls `func(query, values, qrm.one | qrm.none)`
## Conversion Helpers
The library provides several helper functions to convert javascript types into their proper PostgreSQL presentation that can be passed
directly into queries or functions as parameters. All of such helper functions are located within namespace [pgp.as], and each function
returns a formatted string when successful or throws an error when it fails.
## Custom Type Formatting
When we pass `values` as a single parameter or inside an array, it is verified to be an object
that supports function `formatDBType`, as either its own or inherited. And if the function exists,
its return result overrides both the actual value and the formatting syntax for parameter `query`.
This allows usage of your own custom types as formatting parameters for the queries, as well as
overriding formatting for standard object types, such as `Date` and `Array`.
**Example: your own type formatting**
```js
function Money(m) {
this.amount = m;
this.formatDBType = function () {
// return a string with 2 decimal points;
return this.amount.toFixed(2);
}
}
```
**Example: overriding standard types**
```js
Date.prototype.formatDBType = function () {
// format Date as a local timestamp;
return this.getTime();
};
```
Function `formatDBType` is allowed to return absolutely anything, including:
* instance of another object that supports its own custom formatting;
* instance of another object that doesn't have its own custom formatting;
* another function, with recursion of any depth;
Please note that the return result from `formatDBType` may even affect the
formatting syntax expected within parameter `query`, as explained below.
If you pass in `values` as an object that has function `formatDBType`,
and that function returns an array, then your `query` is expected to use
`$1, $2` as the formatting syntax.
And if `formatDBType` in that case returns a custom-type object that doesn't support
custom formatting, then `query` will be expected to use `$*propName*` as the formatting syntax.
### Raw Custom Types
This features allows overriding `raw` flag for the values returned from custom types.
Any custom type or standard type that implements function `formatDBType` can also set
property `_rawDBType = true` to force raw variable formatting on the returned value.
This makes the custom type formatting ultimately flexible, as there is no limitation
as to how a custom type can format its value.
For example, some special types, like UUID, do not have natural presentation in JavaScript,
so they have to be converted into text strings when passed into the query formatting.
For an array of UUID-s, for instance, you would have to explicitly cast the formatted value
with `::uuid[]` appended at the end of the variable.
You can implement your own presentation for UUID that does not require extra casting:
```js
function UUID(value) {
this.uuid = value;
this._rawDBType = true; // force raw format on output;
this.formatDBType = function () {
// alternatively, you can set flag
// _rawDBType during this call:
// this._rawDBType = true;
return this.uuid;
};
}
```
When you chain one custom-formatting type to return another one, please note that
setting `_rawDBType` on any level will set the flag for the entire chain.
## Query Files
Use of external SQL files (via [QueryFile]) offers many advantages:
* Much cleaner JavaScript code, with all SQL kept in external files;
* Much easier to write large and well-formatted SQL, with comments and whole revisions;
* Changes in external SQL can be automatically re-loaded (option `debug`), without restarting the app;
* Pre-formatting SQL upon loading (option `params`), making a two-step SQL formatting very easy;
* Parsing and minifying SQL (options `minify`/`compress`), for early error detection and smaller queries.
Example:
```js
// Helper for linking to external query files:
function sql(file) {
// consider using here: path.join(__dirname, file)
return new pgp.QueryFile(file, {minify: true});
}
// Create QueryFile globally, once per file:
var sqlFindUser = sql('./sql/findUser.sql');
db.one(sqlFindUser, {id: 123})
.then(user=> {
console.log(user);
})
.catch(error=> {
if (error instanceof pgp.errors.QueryFileError) {
// => the error is related to our QueryFile
}
});
```
File `findUser.sql`:
```sql
/*
multi-line comment
*/
SELECT name, dob -- single-line comment
FROM Users
WHERE id = ${id}
```
Every query method of the library can accept type [QueryFile] as its `query` parameter.
The type never throws any error, leaving it for query methods to reject with [QueryFileError].
You should only create a single instance of [QueryFile] per file, and then reuse that instance throughout the application.
Notable features of [QueryFile]:
* `debug` mode, to make every query request check if the file has changed since it was last read, and if so - read it afresh.
This way you can write sql queries and see immediate updates without having to restart your application.
* Option `params` is for static SQL pre-formatting, to inject certain values only once, like a schema name or a
configurable table name.
In version 5.2.0, support for type [QueryFile] was also integrated into the query formatting engine. See method [as.format].
## Tasks
A task represents a shared connection to be used within a callback function. The callback can be either a regular function or an ES6 generator.
A transaction, for example, is just a special type of task, wrapped in `CONNECT->COMMIT/ROLLBACK`.
```js
db.task(function (t) {
// `t` and `this` here are the same;
// execute a chain of queries;
})
.then(function (data) {
// success;
})
.catch(function (error) {
// failed;
});
```
The purpose of tasks is simply to provide a shared connection context within the callback function to execute and return
a promise chain, and then automatically release the connection.
## Transactions
A transaction is a special type of task that automatically executes `BEGIN` + `COMMIT`/`ROLLBACK`:
1. Acquires a new connection;
2. Executes `BEGIN` command;
3. Invokes your callback function (or generator) with the connection object;
4. Executes `COMMIT`, if the callback resolves, or `ROLLBACK`, if the callback rejects or throws an error;
5. Releases the connection (detached chains only);
6. Resolves with the callback result, if successful; rejects with the reason when fails.
```js
db.tx(function (t) {
// `t` and `this` here are the same;
// creating a sequence of transaction queries:
var q1 = this.none('update users set active=$1 where id=$2', [true, 123]);
var q2 = this.one('insert into audit(entity, id) values($1, $2) returning id',
['users', 123]);
// returning a promise that determines a successful transaction:
return this.batch([q1, q2]); // all of the queries are to be resolved;
})
.then(function (data) {
console.log(data); // printing successful transaction output;
})
.catch(function (error) {
console.log(error); // printing the error;
});
```
A detached transaction acquires a connection and exposes object `t`=`this` to let all containing queries
execute on the same connection.
### Nested Transactions
Nested transactions automatically share the connection between all levels.
This library sets no limitation as to the depth (nesting levels) of transactions supported.
Example:
```javascript
db.tx(function (t) {
// `t` and `this` here are the same;
var queries = [
this.none('drop table users;'),
this.none('create table users(id serial not null, name text not null)')
];
for (var i = 1; i <= 100; i++) {
queries.push(this.none('insert into users(name) values($1)', 'name-' + i));
}
queries.push(
this.tx(function (t1) {
// t1 = this != t;
return this.tx(function (t2) {
// t2 = this != t1 != t;
return this.one('select count(*) from users');
});
}));
return this.batch(queries);
})
.then(function (data) {
console.log(data); // printing transaction result;
})
.catch(function (error) {
console.log(error); // printing the error;
});
```
### Limitations
It is important to know that PostgreSQL doesn't have proper support for nested transactions, it only
supports *partial rollbacks* via [savepoints](http://www.postgresql.org/docs/9.4/static/sql-savepoint.html) inside transactions.
The difference between the two techniques is huge, as explained further.
Proper support for nested transactions means that the result of a successful sub-transaction isn't rolled back
when its parent transaction is rolled back. But with PostgreSQL save-points, if you roll-back the top-level
transaction, the result of all inner save-points is also rolled back.
Save-points are only good for *partial rollbacks*, i.e. you can roll-back results of sub-transactions, with
yet successful *commit* for the top-level transaction. Using promises it is easy to construct your transaction
so it would utilize that logic. This library automatically provides a transaction on the top level, and
save-points for all sub-transactions.
### Synchronous Transactions
A regular task/transaction with a set of independent queries relies on method [batch] to resolve
all queries asynchronously.
However, when it comes to executing a significant number of queries during a bulk `INSERT` or `UPDATE`,
such approach is no longer practical. For one thing, it implies that all requests have been created as promise objects,
which isn't possible when dealing with a huge number of queries, due to memory limitations imposed by NodeJS.
And for another, when one query fails, the rest will continue trying to execute, due to their promise nature,
as being asynchronous.
This is why within each task/transaction we have method [sequence], to be able to execute a strict
sequence of queries one by one, and if one fails - the rest won't try to execute.
```js
function source(index, data, delay) {
// must create and return a promise object dynamically,
// based on the index of the sequence;
switch (index) {
case 0:
return this.query('select 0');
case 1:
return this.query('select 1');
case 2:
return this.query('select 2');
}
// returning or resolving with undefined ends the sequence;
// throwing an error will result in a reject;
}
db.tx(function (t) {
// `t` and `this` here are the same;
return this.sequence(source);
})
.then(function (data) {
console.log(data); // print result;
})
.catch(function (error) {
console.log(error); // print the error;
});
```
Sequence is based on implementation of [spex.sequence].
### Configurable Transactions
In order to be able to fine-tune database requests in a highly asynchronous environment,
PostgreSQL supports *Transaction Snapshots*, plus 3 ways of configuring a transaction:
* [SET TRANSACTION](http://www.postgresql.org/docs/9.4/static/sql-set-transaction.html), to configure the current transaction,
which your can execute as the very first query in your transaction function;
* `SET SESSION CHARACTERISTICS AS TRANSACTION` - setting default transaction properties for the entire session;
* [BEGIN](http://www.postgresql.org/docs/9.4/static/sql-begin.html) + `Transaction Mode` - initiates a pre-configured transaction.
The first method is quite usable, but that means you have to start every transaction with
an initial query to configure the transaction, which can be a bit awkward.
The second approach isn't very usable within a database framework as this one, which relies
on a connection pool, so you don't really know when a new connection is created.
The last method is not usable, because transactions in this library are automatic, executing `BEGIN`
without your control, or so it was until [Transaction Mode] type was added (read further).
---
[Transaction Mode] extends the `BEGIN` command in your transaction with a complete set of configuration parameters.
```js
var TransactionMode = pgp.txMode.TransactionMode;
var isolationLevel = pgp.txMode.isolationLevel;
// Create a reusable transaction mode (serializable + read-only + deferrable):
var tmSRD = new TransactionMode({
tiLevel: isolationLevel.serializable,
readOnly: true,
deferrable: true
});
function myTransaction() {
return this.query('SELECT * FROM table');
}
myTransaction.txMode = tmSRD; // assign transaction mode;
db.tx(myTransaction)
.then(function(){
// success;
});
```
Instead of the default `BEGIN`, such transaction will initiate with the following command:
```
BEGIN ISOLATION LEVEL SERIALIZABLE READ ONLY DEFERRABLE
```
Transaction Mode is set via property `txMode` on the transaction function.
This is the most efficient and best-performing way of configuring transactions. In combination with
*Transaction Snapshots* you can make the most out of transactions in terms of performance and concurrency.
## Generators
If you prefer writing asynchronous code in a synchronous manner, you can implement your tasks and transactions as generators.
```js
function * getUser(t) {
// `t` and `this` here are the same;
let user = yield this.oneOrNone('select * from users where id = $1', 123);
return yield user || this.one('insert into users(name) values($1) returning *', 'John');
}
db.task(getUser)
.then(function (user) {
// success;
})
.catch(function (error) {
// error;
});
```
The library verifies whether the callback function is a generator, and executes it accordingly.
# Advanced
## Initialization Options
When initializing the library, you can pass object `options` with a set of global properties.
See [API / options](http://vitaly-t.github.io/pg-promise/module-pg-promise.html) for complete list of supported options.
---
#### pgFormatting
By default, **pg-promise** provides its own implementation of the query formatting,
as explained in [Queries and Parameters](#queries-and-parameters).
If, however, you want your queries formatted by the [PG] library, set parameter `pgFormatting`
to be `true` when initializing the library, and every query formatting will redirect to the [PG]'s implementation.
Although this has a huge implication to the library's functionality, it is not within the scope of this project to detail.
For any further reference you should use documentation of the [PG] library.
Below is just some of the query-formatting features implemented by [pg-promise] that are not in [node-postgres]:
* [Custom Type Formatting](#custom-type-formatting)
* Single-value formatting: [pg-promise] doesn't require use of an array when passing a single value;
* [Raw-Text](https://github.com/vitaly-t/pg-promise/wiki/Learn-by-Example#raw-text) support: injecting raw/pre-formatted text values into the query;
* Functions as formatting parameters, with the actual values returned from the callbacks;
* [PostgreSQL Array Constructors](http://www.postgresql.org/docs/9.1/static/arrays.html#ARRAYS-INPUT) are used when formatting arrays,
not the old string syntax;
* Automatic conversion of numeric `NaN`, `+Infinity` and `-Infinity` into their string presentation;
* Support for [this reference](#this-reference);
* Automatic [QueryFile] support
**NOTE:** Formatting parameters for calling functions (methods `func` and `proc`) is not affected by this override.
When needed, use the generic `query` instead to invoke functions with redirected query formatting.
---
#### promiseLib
By default, **pg-promise** uses ES6 Promise. If your version of NodeJS doesn't support ES6 Promise,
or you want a different promise library to be used, set this property to the library's instance.
Example of switching over to [Bluebird]:
```js
var promise = require('bluebird');
var options = {
promiseLib: promise
};
var pgp = require('pg-promise')(options);
```
[Promises/A+] libraries that implement a recognizable promise signature and work automatically:
* **ES6 Promise** - used by default, though it doesn't have `done()` or `finally()`.
* [Bluebird] - best alternative all around;
* [Promise] - very solid library;
* [When] - quite old, not the best support;
* [Q] - most widely used;
* [RSVP] - doesn't have `done()`, use `finally/catch` instead
* [Lie] - doesn't have `done()`.
If you pass in a library that doesn't implement a recognizable promise signature, **pg-promise** will
throw error `Invalid promise library specified.` during initialization.
For such libraries you can use [Promise Adapter] to make them compatible with **pg-promise**,
mostly needed by smaller and simplified [Conformant Implementations](https://promisesaplus.com/implementations).
## Library de-initialization
When exiting your application, you can optionally call [pgp.end]:
```js
pgp.end(); // terminate the database connection pool
```
This will release [pg] connection pool globally and make sure that the process terminates without any delay.
If you do not call it, your process may be waiting for 30 seconds (default for [poolIdleTimeout](https://github.com/brianc/node-postgres/blob/master/lib/defaults.js#L44)),
waiting for the connection to expire in the pool.
If, however you normally exit your application by killing the NodeJS process, then you don't need to use it.
# History
For the list of all changes see the [history log](history.md).
# License
Copyright (c) 2016 Vitaly Tomilov (vitaly.tomilov@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.
[Configuration Object]:https://github.com/vitaly-t/pg-promise/wiki/Connection-Syntax#configuration-object
[Connection String]:https://github.com/vitaly-t/pg-promise/wiki/Connection-Syntax#connection-string
[each]:http://vitaly-t.github.io/pg-promise/Database.html#.each
[map]:http://vitaly-t.github.io/pg-promise/Database.html#.map
[Connection Syntax]:https://github.com/vitaly-t/pg-promise/wiki/Connection-Syntax
[helpers]:http://vitaly-t.github.io/pg-promise/helpers.html
[QueryFile]:http://vitaly-t.github.io/pg-promise/QueryFile.html
[QueryFileError]:http://vitaly-t.github.io/pg-promise/QueryFileError.html
[PreparedStatement]:http://vitaly-t.github.io/pg-promise/PreparedStatement.html
[ParameterizedQuery]:http://vitaly-t.github.io/pg-promise/ParameterizedQuery.html
[Database]:http://vitaly-t.github.io/pg-promise/Database.html
[QueryResultError]:http://vitaly-t.github.io/pg-promise/QueryResultError.html
[Native Bindings]:https://github.com/brianc/node-postgres#native-bindings
[Initialization Options]:#advanced
[pgp.end]:http://vitaly-t.github.io/pg-promise/module-pg-promise.html#~end
[pgp.as]:http://vitaly-t.github.io/pg-promise/formatting.html
[as.value]:http://vitaly-t.github.io/pg-promise/formatting.html#.value
[as.format]:http://vitaly-t.github.io/pg-promise/formatting.html#.format
[as.name]:http://vitaly-t.github.io/pg-promise/formatting.html#.name
[batch]:http://vitaly-t.github.io/pg-promise/Task.html#.batch
[sequence]:http://vitaly-t.github.io/pg-promise/Task.html#.sequence
[Protocol API]:http://vitaly-t.github.io/pg-promise/index.html
[API]:http://vitaly-t.github.io/pg-promise/index.html
[API Documentation]:http://vitaly-t.github.io/pg-promise/index.html
[Transaction Mode]:http://vitaly-t.github.io/pg-promise/txMode.TransactionMode.html
[pg-minify]:https://github.com/vitaly-t/pg-minify
[pg-monitor]:https://github.com/vitaly-t/pg-monitor
[pg-promise]:https://github.com/vitaly-t/pg-promise
[PG]:https://github.com/brianc/node-postgres
[pg]:https://github.com/brianc/node-postgres
[node-postgres]:https://github.com/brianc/node-postgres
[Promises/A+]:https://promisesaplus.com/
[Promise]:https://github.com/then/promise
[Bluebird]:https://github.com/petkaantonov/bluebird
[When]:https://github.com/cujojs/when
[Q]:https://github.com/kriskowal/q
[RSVP]:https://github.com/tildeio/rsvp.js
[Lie]:https://github.com/calvinmetcalf/lie
[Learn by Example]:https://github.com/vitaly-t/pg-promise/wiki/Learn-by-Example
[Promise Adapter]:https://github.com/vitaly-t/pg-promise/wiki/Promise-Adapter
[spex.sequence]:http://vitaly-t.github.io/spex/global.html#sequence
[Result]:https://github.com/brianc/node-postgres/blob/master/lib/result.js#L6