psycopg/psycopg2
1
1
Fork 0
mirror of https://github.com/psycopg/psycopg2.git synced 2024-11-26 02:43:43 +03:00
Code Issues Packages Projects Releases Wiki Activity

Notifcation example improved.

Browse Source
This commit is contained in:
Daniele Varrazzo 2010-11-06 20:59:10 +00:00
parent 7276c4a6b1
commit 2f582da1f0
1 changed files with 16 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

28
doc/src/advanced.rst
View File

@ -208,10 +208,6 @@ read:
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
facilities offered by PostgreSQL commands |LISTEN|_ and |NOTIFY|_. Please
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
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.
Because of the way sessions interact with notifications (see |NOTIFY|_
@ -253,26 +249,34 @@ something to read::
curs = conn.cursor()
curs.execute("LISTEN test;")
# Payload only available since PostgreSQL 9.0
print "Waiting for 'NOTIFY test', 'hello'"
print "Waiting for notifications on channel 'test'"
while 1:
if select.select([conn],[],[],5) == ([],[],[]):
print "Timeout"
else:
conn.poll()
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
:program:`psql` shell, the output may look similar to::
Running the script and executing a command such as :sql:`NOTIFY test, 'hello'`
in a separate :program:`psql` shell, the output may look similar to::
Waiting for 'NOTIFY test'
Waiting for notifications on channel 'test'
Timeout
Timeout
Got NOTIFY: Notify(6535, 'test', 'hello')
Got NOTIFY: 6535 test hello
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::