# Postgrex
[](https://travis-ci.org/ericmj/postgrex)
PostgreSQL driver for Elixir.
Documentation: http://hexdocs.pm/postgrex/
## Usage
Add Postgrex as a dependency in your `mix.exs` file.
```elixir
def deps do
[{:postgrex, "~> 0.6"} ]
end
```
After you are done, run `mix deps.get` in your shell to fetch and compile Postgrex. Start an interactive Elixir shell with `iex -S mix`.
```iex
iex> {:ok, pid} = Postgrex.Connection.start_link(hostname: "localhost", username: "postgres", password: "postgres", database: "postgres")
{:ok, #PID<0.69.0>}
iex> Postgrex.Connection.query!(pid, "SELECT user_id, text FROM comments", [])
%Postgrex.Result{command: :select, empty?: false, columns: ["user_id", "text"], rows: [{3,"hey"},{4,"there"}], size: 2}}
iex> Postgrex.Connection.query!(pid, "INSERT INTO comments (user_id, text) VALUES (10, 'heya')", [])
%Postgrex.Result{command: :insert, columns: nil, rows: nil, num_rows: 1}}
```
## Features
* Automatic decoding and encoding of Elixir values to and from PostgreSQL's binary format
* User defined extensions for encoding and decoding any PostgresSQL type
* Supports PostgreSQL 8.4, 9.0, 9.1, 9.2, 9.3, and 9.4
## Data representation
PostgreSQL Elixir
---------- ------
NULL nil
bool true | false
char "é"
int 42
float 42.0
text "eric"
bytea <<42>>
numeric #Decimal<42.0> *
date %Postgrex.Date{year: 2013, month: 10, day: 12}
time %Postgrex.Time{hour: 0, min: 37, sec: 14, msec: 0}
timestamp(tz) %Postgrex.Timestamp{year: 2013 month: 10, day: 12, hour: 0, min: 37, sec: 14, msec: 0}
interval %Postgrex.Interval{months: 14, days: 40, secs: 10920}
array [1, 2, 3]
composite type {42, "title", "content"}
range %Postgrex.Range{lower: 1, upper: 5}
uuid <<160,238,188,153,156,11,78,248,187,109,107,185,189,56,10,17>>
\* [Decimal](http://github.com/ericmj/decimal)
## Extensions
Extensions are used to extend Postgrex' built-in type encoding/decoding.
Below is an example of an extension that supports encoding/decoding Elixir maps
to the Postgres' JSON type.
```elixir
defmodule Extensions.JSON do
alias Postgrex.TypeInfo
@behaviour Postgrex.Extension
def init(_parameters, opts),
do: Keyword.fetch!(opts, :library)
def matching(_library),
do: [type: "json"]
def format(_library),
do: :binary
def encode(%TypeInfo{type: "json"}, map, _state, library),
do: library.encode!(map)
def decode(%TypeInfo{type: "json"}, json, _state, library),
do: library.decode!(json)
end
Postgrex.Connection.start_link(extensions: [{Extensions.JSON, library: Poison}], ...)
```
## Contributing
To contribute you need to compile Postgrex from source and test it:
```
$ git clone https://github.com/ericmj/postgrex.git
$ cd postgrex
$ mix test
```
The tests requires some modifications to your [hba file](http://www.postgresql.org/docs/9.3/static/auth-pg-hba-conf.html). The path to it can be found by running `$ psql -U postgres -c "SHOW hba_file"` in your shell. Put the following above all other configurations (so that they override):
```
host all postgrex_md5_pw 127.0.0.1/32 md5
host all postgrex_cleartext_pw 127.0.0.1/32 password
```
The server needs to be restarted for the changes to take effect. Additionally you need to setup a Postgres user with the same username as the local user and give it trust or ident in your hba file. Or you can export $PGUSER and $PGPASS before running tests.
## License
Copyright 2013 Eric Meadows-Jönsson
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
