postgresql2 0.5.1+1

PostgreSQL database driver for Dart #

A temporary fork of Greg's PostgreSQL driver using conserved substitution respecting strings and @@ operators, also optimizing the pool implementation aggressivly.

encodeString() supports trimNull to work around the null character issue

Pool.connect() returns as soon as possible when failed to connect to database. Also, it resumes if the connection is back. Caller can detect it as follows:

ex is PostgresqlException
&& const [PE_CONNECTION_TIMEOUT, PE_CONNECTION_CLOSED,
		PE_CONNECTION_FAILED, PE_POOL_STOPPED].contains(ex.exception)

Build Status

Basic usage #

Obtaining a connection #

var uri = 'postgres://username:password@localhost:5432/database';
connect(uri).then((conn) {
	// ...
});

SSL connections #

Set the sslmode to require by appending this to the connection uri. This driver only supports sslmode=require, if sslmode is ommitted the driver will always connect without using SSL.

var uri = 'postgres://username:password@localhost:5432/database?sslmode=require';
connect(uri).then((conn) {
	// ...
});

Querying #

conn.query('select color from crayons').toList().then((rows) {
	for (var row in rows) {
		print(row.color); // Refer to columns by name,
		print(row[0]);    // Or by column index.
	}
});

Executing #

conn.execute("update crayons set color = 'pink'").then((rowsAffected) {
	print(rowsAffected);
});

Query Parameters #

Query parameters can be provided using a map. Strings will be escaped to prevent SQL injection vulnerabilities.

conn.query('select color from crayons where id = @id', {'id': 5})
  .toList()
	.then((result) { print(result); });

conn.execute('insert into crayons values (@id, @color)',
             {'id': 1, 'color': 'pink'})
	.then((_) { print('done.'); });

Closing the connection #

You must remember to call Connection.close() when you're done. This won't be done automatically for you.

Conversion of Postgresql datatypes. #

Below is the mapping from Postgresql types to Dart types. All types which do not have an explicit mapping will be returned as a String in Postgresql's standard text format. This means that it is still possible to handle all types, as you can parse the string yourself.

     Postgresql type                 Dart type
	boolean                         bool
	int2, int4, int8                int
	float4, float8                  double
	numeric                         String
	timestamp, timestamptz, date    Datetime
	json, jsonb                     Map/List
	All other types                 String

Mapping the results of a query to an object #

class Crayon {
	String color;
	int length;
}

conn.query('select color, length from crayons')
	.map((row) => new Crayon()
	                     ..color = row.color
	                     ..length = row.length)
	.toList()
	.then((List<Crayon> crayons) {
		for (var c in crayons) {
			print(c is Crayon);
			print(c.color);
			print(c.length);
		}
	});

Or for an immutable object:

class ImmutableCrayon {
	ImmutableCrayon(this.color, this.length);
	final String color;
	final int length;
}

conn.query('select color, length from crayons')
  .map((row) => new ImmutableCrayon(row.color, row.length))
     .toList()
	.then((List<ImmutableCrayon> crayons) {
		for (var c in crayons) {
			print(c is ImmutableCrayon);
			print(c.color);
			print(c.length);
		}
	});

Query queueing #

Queries are queued and executed in the order in which they were queued.

So if you're not concerned about handling errors, you can write code like this:

conn.execute("create table crayons (color text, length int)");
conn.execute("insert into crayons values ('pink', 5)");
conn.query("select color from crayons").single.then((crayon) {
	print(crayon.color); // prints 'pink'
});

Query streaming #

Connection.query() returns a Stream of results. You can use each row as soon as it is received, or you can wait till they all arrive by calling Stream.toList().

Connection pooling #

In server applications, a connection pool can be used to avoid the overhead of obtaining a connection for each request.

import 'package:postgresql2/pool.dart';

main() {
  var uri = 'postgres://username:password@localhost:5432/database';
  var pool = new Pool(uri, minConnections: 2, maxConnections: 5);
  pool.messages.listen(print);
  pool.start().then((_) {
    print('Min connections established.');
    pool.connect().then((conn) { // Obtain connection from pool
      conn.query("select 'oi';")
        .toList()
        .then(print)
        .then((_) => conn.close()) // Return connection to pool
        .catchError((err) => print('Query error: $err'));
    });
  });
}

Example program #

Add postgresql to your pubspec.yaml file, and run pub install.

name: postgresql_example
dependencies:
  postgresql: any
import 'package:postgresql2/postgresql.dart';

void main() {
  var uri = 'postgres://testdb:password@localhost:5432/testdb';
  var sql = "select 'oi'"; 
  connect(uri).then((conn) {
    conn.query(sql).toList()
    	.then((result) {
    		print('result: $result');
    	})
    	.whenComplete(() {
    		conn.close();
    	});
  });
}

Testing #

To run the unit tests you will need to create a database, and edit 'test/config.yaml' accordingly.

Creating a database for testing #

Change to the postgres user and run the administration commands.

sudo su postgres
createuser --pwprompt testdb
  Enter password for new role: password
  Enter it again: password
  Shall the new role be a superuser? (y/n) n
  Shall the new role be allowed to create databases? (y/n) n
  Shall the new role be allowed to create more new roles? (y/n) n
createdb --owner testdb testdb
exit

Check that it worked by logging in.

psql -h localhost -U testdb -W

Enter "\q" to quit from the psql console.

License #

BSD

http://www.postgresql.org/docs/9.2/static/index.html http://www.dartlang.org/

Who Uses #

  • Quire - a simple, collaborative, multi-level task management tool.
  • Keikai - a sophisticated spreadsheet for big data

Version 0.3.4 #

  • Update broken crypto dependency.

Version 0.3.3 #

  • Fix #73 Properly encode/decode connection uris. Thanks to Martin Manev.
  • Permit connection without a password. Thanks to Jirka Daněk.

Version 0.3.2 #

  • Improve handing of datetimes. Thanks to Joe Conway.
  • Remove manually cps transformed async code.
  • Fix #58: Establish connections concurrently. Thanks to Tom Yeh.
  • Fix #67: URI encode db name so spaces can be used in db name. Thanks to Chad Schwendiman.
  • Fix #69: Empty connection pool not establishing connections.

Version 0.3.1+1 #

  • Expose column information via row.getColumns(). Credit to Jesper Håkansson for this change.

Version 0.3.0 #

  • A new connection pool with more configuration options.
  • Support for json and timestamptz types.
  • Utc time zone support.
  • User customisable type conversions.
  • Improved error handling.
  • Connection.onClosed has been removed.
  • Some api has been renamed, the original names are still functional but marked as deprecated.
    • import 'package:postgresql/postgresql_pool.dart' => import 'package:postgresql/pool.dart'
    • Pool.destroy() => Pool.stop()
    • The constants were upper case and int type. Now typed and lower camel case to match the style guide.
    • Connection.unhandled => Connection.messages
    • Connection.transactionStatus => Connection.transactionState

Thanks to Tom Yeh and Petar Sabev for their helpful feedback.

Use this package as a library

1. Depend on it

Add this to your package's pubspec.yaml file:


dependencies:
  postgresql2: ^0.5.1+1

2. Install it

You can install packages from the command line:

with pub:


$ pub get

with Flutter:


$ flutter pub get

Alternatively, your editor might support pub get or flutter pub get. Check the docs for your editor to learn more.

3. Import it

Now in your Dart code, you can use:


import 'package:postgresql2/constants.dart';
import 'package:postgresql2/pool.dart';
import 'package:postgresql2/postgresql.dart';
  
Popularity:
Describes how popular the package is relative to other packages. [more]
58
Health:
Code health derived from static analysis. [more]
39
Maintenance:
Reflects how tidy and up-to-date the package is. [more]
67
Overall:
Weighted score of the above. [more]
54
Learn more about scoring.

We analyzed this package on Jul 15, 2019, and provided a score, details, and suggestions below. Analysis was completed with status completed using:

  • Dart: 2.4.0
  • pana: 0.12.19

Platforms

Detected platforms: Flutter, other

Platform components identified in package: io.

Health issues and suggestions

Fix lib/src/mock/mock_server.dart. (-25.38 points)

Analysis of lib/src/mock/mock_server.dart failed with 1 error, 1 hint:

line 106 col 7: Missing concrete implementations of Socket.getRawOption and Socket.setRawOption.

line 146 col 3: Avoid return types on setters.

Fix lib/src/postgresql_impl/connection.dart. (-12.66 points)

Analysis of lib/src/postgresql_impl/connection.dart reported 27 hints, including:

line 59 col 7: DO use curly braces for all flow control structures.

line 84 col 7: DO use curly braces for all flow control structures.

line 158 col 7: DO use curly braces for all flow control structures.

line 191 col 7: DO use curly braces for all flow control structures.

line 232 col 9: DO use curly braces for all flow control structures.

Fix lib/src/pool_settings_impl.dart. (-9.08 points)

Analysis of lib/src/pool_settings_impl.dart reported 19 hints, including:

line 15 col 26: Use = to separate a named parameter from its default value.

line 16 col 26: Use = to separate a named parameter from its default value.

line 17 col 24: Use = to separate a named parameter from its default value.

line 18 col 23: Use = to separate a named parameter from its default value.

line 19 col 28: Use = to separate a named parameter from its default value.

Fix additional 15 files with analysis or formatting issues. (-41.87 points)

Additional issues in the following files:

  • lib/src/postgresql_impl/type_converter.dart (18 hints)
  • lib/src/pool_impl.dart (14 hints)
  • lib/src/substitute.dart (13 hints)
  • lib/src/duration_format.dart (11 hints)
  • lib/src/postgresql_impl/settings.dart (11 hints)
  • lib/src/buffer.dart (7 hints)
  • lib/src/mock/mock.dart (3 hints)
  • lib/src/postgresql_impl/query.dart (3 hints)
  • lib/src/mock/mock_socket_server.dart (2 hints)
  • lib/src/postgresql_impl/messages.dart (2 hints)
  • lib/src/postgresql_impl/constants.dart (1 hint)
  • lib/src/protocol.dart (1 hint)
  • lib/constants.dart (Run dartfmt to format lib/constants.dart.)
  • lib/pool.dart (Run dartfmt to format lib/pool.dart.)
  • lib/postgresql.dart (Run dartfmt to format lib/postgresql.dart.)

Maintenance issues and suggestions

Use constrained dependencies. (-20 points)

The pubspec.yaml contains 2 dependencies without version constraints. Specify version ranges for the following dependencies: convert, crypto.

Maintain an example. (-10 points)

Create a short demo in the example/ directory to show how to use this package.

Common filename patterns include main.dart, example.dart, and postgresql2.dart. Packages with multiple examples should provide example/README.md.

For more information see the pub package layout conventions.

The description is too long. (-3 points)

Search engines display only the first part of the description. Try to keep the value of the description field in your package's pubspec.yaml file between 60 and 180 characters.

Dependencies

Package Constraint Resolved Available
Direct dependencies
Dart SDK >=2.0.0-dev <3.0.0
convert >=1.0.0 2.1.1
crypto >=2.0.0 2.0.6
Transitive dependencies
charcode 1.1.2
collection 1.14.11
typed_data 1.1.6
Dev dependencies
test any
yaml any

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