Package pq is a pure Go Postgres driver for the database/sql package.
In most cases clients will use the database/sql package instead of
using this package directly. For example:
You can also connect to a database using a URL. For example:
Similarly to libpq, when establishing a connection using pq you are expected to
supply a connection string containing zero or more parameters.
A subset of the connection parameters supported by libpq are also supported by pq.
Additionally, pq also lets you specify run-time parameters (such as search_path or work_mem)
directly in the connection string. This is different from libpq, which does not allow
run-time parameters in the connection string, instead requiring you to supply
them in the options parameter.
For compatibility with libpq, the following special connection parameters are
Valid values for sslmode are:
for more information about connection string parameters.
Use single quotes for values that contain whitespace:
A backslash will escape the next character in values:
Note that the connection parameter client_encoding (which sets the
text encoding for the connection) may be set but must be "UTF8",
matching with the same rules as Postgres. It is an error to provide
any other value.
In addition to the parameters listed above, any run-time parameter that can be
set at backend start time can be set in the connection string. For more
Most environment variables as specified at http://www.postgresql.org/docs/current/static/libpq-envars.html
supported by libpq are also supported by pq. If any of the environment
variables not supported by pq are set, pq will panic during connection
establishment. Environment variables have a lower precedence than explicitly
provided connection parameters.
The pgpass mechanism as described in http://www.postgresql.org/docs/current/static/libpq-pgpass.html
is supported, but on Windows PGPASSFILE must be specified explicitly.
database/sql does not dictate any specific format for parameter
markers in query strings, and pq uses the Postgres-native ordinal markers,
as shown above. The same marker can be reused for the same parameter:
pq does not support the LastInsertId() method of the Result type in database/sql.
To return the identifier of an INSERT (or UPDATE or DELETE), use the Postgres
RETURNING clause with a standard Query or QueryRow call:
For more details on RETURNING, see the Postgres documentation:
For additional instructions on querying see the documentation for the database/sql package.
Parameters pass through driver.DefaultParameterConverter before they are handled
by this package. When the binary_parameters connection option is enabled,
byte values are sent directly to the backend as data in binary format.
This package returns the following types for values from the PostgreSQL backend:
All other types are returned directly from the backend as byte values in text format.
pq may return errors of type *pq.Error which can be interrogated for error details:
See the pq.Error type for details.
You can perform bulk imports by preparing a statement returned by pq.CopyIn (or
pq.CopyInSchema) in an explicit transaction (sql.Tx). The returned statement
handle can then be repeatedly "executed" to copy data into the target table.
After all data has been processed you should call Exec() once with no arguments
to flush all buffered data. Any call to Exec() might return an error which
should be handled appropriately, but because of the internal buffering an error
returned by Exec() might not be related to the data passed in the call that
CopyIn uses COPY FROM internally. It is not possible to COPY outside of an
explicit transaction in pq.
PostgreSQL supports a simple publish/subscribe model over database
connections. See http://www.postgresql.org/docs/current/static/sql-notify.html
for more information about the general mechanism.
To start listening for notifications, you first have to open a new connection
to the database by calling NewListener. This connection can not be used for
anything other than LISTEN / NOTIFY. Calling Listen will open a "notification
channel"; once a notification channel is open, a notification generated on that
channel will effect a send on the Listener.Notify channel. A notification
channel will remain open until Unlisten is called, though connection loss might
result in some notifications being lost. To solve this problem, Listener sends
a nil pointer over the Notify channel any time the connection is re-established
following a connection loss. The application can get information about the
state of the underlying connection by setting an event callback in the call to
A single Listener can safely be used from concurrent goroutines, which means
that there is often no need to create more than one Listener in your
application. However, a Listener is always connected to a single database, so
you will need to create a new Listener instance for every database you want to
receive notifications in.
The channel name in both Listen and Unlisten is case sensitive, and can contain
any characters legal in an identifier (see
for more information). Note that the channel name will be truncated to 63
bytes by the PostgreSQL server.
You can find a complete, working example of Listener usage at