Postgrex v0.11.1 Postgrex

PostgreSQL driver for Elixir.

This module handles the connection to Postgres, providing support for queries, transactions, connection backoff, logging, pooling and more.

Note that the notifications API (pub/sub) supported by Postgres is handled by Postgrex.Notifications. Hence, to use this feature, you need to start a separate (notifications) connection.

Summary

Types

A connection process name, pid or reference

Functions

Returns a supervisor child specification for a DBConnection pool

Closes an (extended) prepared query and returns :ok or {:error, %Postgrex.Error{}} if there was an error. Closing a query releases any resources held by postgresql for a prepared query with that name. See Postgrex.Query for the query data

Closes an (extended) prepared query and returns :ok or raises Postgrex.Error if there was an error. See close/3

Runs an (extended) prepared query and returns the result as {:ok, %Postgrex.Result{}} or {:error, %Postgrex.Error{}} if there was an error. Parameters are given as part of the prepared query, %Postgrex.Query{}. See the README for information on how Postgrex encodes and decodes Elixir values by default. See Postgrex.Query for the query data and Postgrex.Result for the result data

Runs an (extended) prepared query and returns the result or raises Postgrex.Error if there was an error. See execute/4

Returns a cached map of connection parameters

Prepares an (extended) query and returns the result as {:ok, %Postgrex.Query{}} or {:error, %Postgrex.Error{}} if there was an error. Parameters can be set in the query as $1 embedded in the query string. To execute the query call execute/4. To close the prepared query call close/3. See Postgrex.Query for the query data

Prepares an (extended) query and returns the prepared query or raises Postgrex.Error if there was an error. See prepare/4

Runs an (extended) query and returns the result as {:ok, %Postgrex.Result{}} or {:error, %Postgrex.Error{}} if there was an error. Parameters can be set in the query as $1 embedded in the query string. Parameters are given as a list of elixir values. See the README for information on how Postgrex encodes and decodes Elixir values by default. See Postgrex.Result for the result data

Runs an (extended) query and returns the result or raises Postgrex.Error if there was an error. See query/3

Rollback a transaction, does not return

Start the connection process and connect to postgres

Acquire a lock on a connection and run a series of requests inside a transaction. The result of the transaction fun is return inside an :ok tuple: {:ok, result}

Types

conn :: DBConnection.conn

A connection process name, pid or reference.

A connection reference is used when making multiple requests to the same connection, see transaction/3 and :after_connect in start_link/1.

Functions

child_spec(opts)

Specs

Returns a supervisor child specification for a DBConnection pool.

close(conn, query, opts \\ [])

Specs

close(conn, Postgrex.Query.t, Keyword.t) ::
  :ok |
  {:error, Postgrex.Error.t}

Closes an (extended) prepared query and returns :ok or {:error, %Postgrex.Error{}} if there was an error. Closing a query releases any resources held by postgresql for a prepared query with that name. See Postgrex.Query for the query data.

Options

  • :pool_timeout - Time to wait in the queue for the connection (default: 5000)
  • :queue - Whether to wait for connection in a queue (default: true);
  • :timeout - Close request timeout (default: 5000);
  • :pool - The pool module to use, must match that set on start_link/1, see DBConnection

Examples

query = Postgrex.prepare!(conn, "CREATE TABLE posts (id serial, title text)")
Postgrex.close(conn, query)
close!(conn, query, opts \\ [])

Specs

close!(conn, Postgrex.Query.t, Keyword.t) :: :ok

Closes an (extended) prepared query and returns :ok or raises Postgrex.Error if there was an error. See close/3.

execute(conn, query, params, opts \\ [])

Specs

execute(conn, Postgrex.Query.t, list, Keyword.t) ::
  {:ok, Postgrex.Result.t} |
  {:error, Postgrex.Error.t}

Runs an (extended) prepared query and returns the result as {:ok, %Postgrex.Result{}} or {:error, %Postgrex.Error{}} if there was an error. Parameters are given as part of the prepared query, %Postgrex.Query{}. See the README for information on how Postgrex encodes and decodes Elixir values by default. See Postgrex.Query for the query data and Postgrex.Result for the result data.

Options

  • :pool_timeout - Time to wait in the queue for the connection (default: 5000)
  • :queue - Whether to wait for connection in a queue (default: true);
  • :timeout - Execute request timeout (default: 5000);
  • :decode_mapper - Fun to map each row in the result to a term after decoding, (default: fn x -> x end);
  • :pool - The pool module to use, must match that set on start_link/1, see DBConnection

Examples

query = Postgrex.prepare!(conn, "CREATE TABLE posts (id serial, title text)")
Postgrex.execute(conn, query, [])

query = Postgrex.prepare!(conn, "SELECT id FROM posts WHERE title like $1")
Postgrex.execute(conn, query, ["%my%"])
execute!(conn, query, params, opts \\ [])

Specs

Runs an (extended) prepared query and returns the result or raises Postgrex.Error if there was an error. See execute/4.

parameters(conn, opts \\ [])

Specs

parameters(conn, Keyword.t) :: %{binary => binary}

Returns a cached map of connection parameters.

Options

  • :pool_timeout - Call timeout (default: 5000)
  • :pool - The pool module to use, must match that set on start_link/1, see DBConnection
prepare(conn, name, statement, opts \\ [])

Specs

prepare(conn, iodata, iodata, Keyword.t) ::
  {:ok, Postgrex.Query.t} |
  {:error, Postgrex.Error.t}

Prepares an (extended) query and returns the result as {:ok, %Postgrex.Query{}} or {:error, %Postgrex.Error{}} if there was an error. Parameters can be set in the query as $1 embedded in the query string. To execute the query call execute/4. To close the prepared query call close/3. See Postgrex.Query for the query data.

Options

  • :pool_timeout - Time to wait in the queue for the connection (default: 5000)
  • :queue - Whether to wait for connection in a queue (default: true);
  • :timeout - Prepare request timeout (default: 5000);
  • :pool - The pool module to use, must match that set on start_link/1, see DBConnection
  • :null - The atom to use as a stand in for postgres’ NULL in encoding and decoding;

Examples

Postgrex.prepare(conn, "CREATE TABLE posts (id serial, title text)")
prepare!(conn, name, statement, opts \\ [])

Specs

prepare!(conn, iodata, iodata, Keyword.t) :: Postgrex.Query.t

Prepares an (extended) query and returns the prepared query or raises Postgrex.Error if there was an error. See prepare/4.

query(conn, statement, params, opts \\ [])

Specs

query(conn, iodata, list, Keyword.t) ::
  {:ok, Postgrex.Result.t} |
  {:error, Postgrex.Error.t}

Runs an (extended) query and returns the result as {:ok, %Postgrex.Result{}} or {:error, %Postgrex.Error{}} if there was an error. Parameters can be set in the query as $1 embedded in the query string. Parameters are given as a list of elixir values. See the README for information on how Postgrex encodes and decodes Elixir values by default. See Postgrex.Result for the result data.

Options

  • :pool_timeout - Time to wait in the queue for the connection (default: 5000)
  • :queue - Whether to wait for connection in a queue (default: true);
  • :timeout - Query request timeout (default: 5000);
  • :decode_mapper - Fun to map each row in the result to a term after decoding, (default: fn x -> x end);
  • :pool - The pool module to use, must match that set on start_link/1, see DBConnection
  • :null - The atom to use as a stand in for postgres’ NULL in encoding and decoding;

Examples

Postgrex.query(conn, "CREATE TABLE posts (id serial, title text)", [])

Postgrex.query(conn, "INSERT INTO posts (title) VALUES ('my title')", [])

Postgrex.query(conn, "SELECT title FROM posts", [])

Postgrex.query(conn, "SELECT id FROM posts WHERE title like $1", ["%my%"])
query!(conn, statement, params, opts \\ [])

Specs

query!(conn, iodata, list, Keyword.t) :: Postgrex.Result.t

Runs an (extended) query and returns the result or raises Postgrex.Error if there was an error. See query/3.

rollback(conn, any)

Specs

rollback(DBConnection.t, any) :: no_return

Rollback a transaction, does not return.

Aborts the current transaction fun. If inside multiple transaction/3 functions, bubbles up to the top level.

Example

{:error, :oops} = Postgrex.transaction(pid, fn(conn) ->
  DBConnection.rollback(conn, :bar)
  IO.puts "never reaches here!"
end)
start_link(opts)

Specs

start_link(Keyword.t) ::
  {:ok, pid} |
  {:error, Postgrex.Error.t | term}

Start the connection process and connect to postgres.

Options

  • :hostname - Server hostname (default: PGHOST env variable, then localhost);
  • :port - Server port (default: 5432);
  • :database - Database (required);
  • :username - Username (default: PGUSER env variable, then USER env var);
  • :password - User password (default PGPASSWORD);
  • :parameters - Keyword list of connection parameters;
  • :timeout - Connect timeout in milliseconds (default: 5000);
  • :ssl - Set to true if ssl should be used (default: false);
  • :ssl_opts - A list of ssl options, see ssl docs;
  • :socket_options - Options to be given to the underlying socket;
  • :sync_connect - Block in start_link/1 until connection is set up (default: false)
  • :extensions - A list of {module, opts} pairs where module is implementing the Postgrex.Extension behaviour and opts are the extension options;
  • :prepare - How to prepare queries, either :named to use named queries or :unnamed to force unnamed queries (default: :named);
  • :after_connect - A function to run on connect, either a 1-arity fun called with a connection reference, {module, function, args} with the connection reference prepended to args or nil, (default: nil)
  • :idle_timeout - Idle timeout to ping postgres to maintain a connection (default: 5000)
  • :backoff_start - The first backoff interval when reconnecting (default: 200);
  • :backoff_max - The maximum backoff interval when reconnecting (default: 15_000);
  • :backoff_type - The backoff strategy when reconnecting, :stop for no backoff and to stop (see :backoff, default: :jitter)
  • :transactions - Set to :strict to error on unexpected transaction state, otherwise set to naive (default: :naive);
  • :pool - The pool module to use, see DBConnection, it must be included with all requests if not the default (default: DBConnection.Connection);
  • :null - The atom to use as a stand in for postgres’ NULL in encoding and decoding (default: nil);
transaction(conn, fun, opts \\ [])

Specs

transaction(conn, (DBConnection.t -> result), Keyword.t) ::
  {:ok, result} |
  {:error, any} when result: var

Acquire a lock on a connection and run a series of requests inside a transaction. The result of the transaction fun is return inside an :ok tuple: {:ok, result}.

To use the locked connection call the request with the connection reference passed as the single argument to the fun. If the connection disconnects all future calls using that connection reference will fail.

rollback/2 rolls back the transaction and causes the function to return {:error, reason}.

transaction/3 can be nested multiple times if the connection reference is used to start a nested transaction. The top level transaction function is the actual transaction.

Options

  • :pool_timeout - Time to wait in the queue for the connection (default: 5000)
  • :queue - Whether to wait for connection in a queue (default: true);
  • :timeout - Transaction timeout (default: 5000);
  • :pool - The pool module to use, must match that set on start_link/1, see DBConnection; *:mode- Set to:savepointto use savepoints instead of an SQL transaction, otherwise set to:transaction(default::transaction); The:timeoutis for the duration of the transaction and all nested transactions and requests. This timeout overrides timeouts set by internal transactions and requests. The:pooland:mode` will be used for all requests inside the transaction function. ## Example {:ok, res} = Postgrex.transaction(pid, fn(conn) -> Postgrex.query!(conn, “SELECT title FROM posts”, []) end)