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Notifcation example improved.

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Daniele Varrazzo 2010-11-06 20:59:10 +00:00
parent 7276c4a6b1
commit 2f582da1f0
1 changed files with 16 additions and 12 deletions
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doc/src/advanced.rst
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@ -208,10 +208,6 @@ read:
Asynchronous notifications Asynchronous notifications
-------------------------- --------------------------
.. versionchanged:: 2.3
Added `~psycopg2.extensions.Notify` object allowing to retrieve
the notification payload if connected to a PostgreSQL 9.0 server.
Psycopg allows asynchronous interaction with other database sessions using the Psycopg allows asynchronous interaction with other database sessions using the
facilities offered by PostgreSQL commands |LISTEN|_ and |NOTIFY|_. Please facilities offered by PostgreSQL commands |LISTEN|_ and |NOTIFY|_. Please
refer to the PostgreSQL documentation for examples about how to use this form of refer to the PostgreSQL documentation for examples about how to use this form of
@ -219,7 +215,7 @@ communication.
Notifications are instances of the `~psycopg2.extensions.Notify` object made Notifications are instances of the `~psycopg2.extensions.Notify` object made
available upon reception in the `connection.notifies` list. Notifications can available upon reception in the `connection.notifies` list. Notifications can
be sent from Python code simply using a :sql:`NOTIFY` command in an be sent from Python code simply executing a :sql:`NOTIFY` command in an
`~cursor.execute()` call. `~cursor.execute()` call.
Because of the way sessions interact with notifications (see |NOTIFY|_ Because of the way sessions interact with notifications (see |NOTIFY|_
@ -253,26 +249,34 @@ something to read::
curs = conn.cursor() curs = conn.cursor()
curs.execute("LISTEN test;") curs.execute("LISTEN test;")
# Payload only available since PostgreSQL 9.0 print "Waiting for notifications on channel 'test'"
print "Waiting for 'NOTIFY test', 'hello'"
while 1: while 1:
if select.select([conn],[],[],5) == ([],[],[]): if select.select([conn],[],[],5) == ([],[],[]):
print "Timeout" print "Timeout"
else: else:
conn.poll() conn.poll()
while conn.notifies: while conn.notifies:
print "Got NOTIFY:", conn.notifies.pop() notify = conn.notifies.pop()
print "Got NOTIFY:", notify.pid, notify.channel, notify.payload
Running the script and executing the command :sql:`NOTIFY test` in a separate Running the script and executing a command such as :sql:`NOTIFY test, 'hello'`
:program:`psql` shell, the output may look similar to:: in a separate :program:`psql` shell, the output may look similar to::
Waiting for 'NOTIFY test' Waiting for notifications on channel 'test'
Timeout Timeout
Timeout Timeout
Got NOTIFY: Notify(6535, 'test', 'hello') Got NOTIFY: 6535 test hello
Timeout Timeout
... ...
Notice that the payload is only available from PostgreSQL 9.0: notifications
received from a previous version server will have the `!payload` attribute set
to the empty string.
.. versionchanged:: 2.3
Added `~psycopg2.extensions.Notify` object and handling notification
payload.
.. index:: .. index::