Psycopg in my project

Plone Support
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1

Hello Community,

I have the following question:

I use in my Plone 5 project the psycopg 2.9.1 library I want to use only the listen function of my PosgreSQL. I have tested it and it seems to work. But in the Zope documentation it says that you should use ZPsycopgDA.

What I don't understand now is why psycopg 2.9.1 works anyway.

Example-Code:

connection.set_isolation_level(ISOLATION_LEVEL_AUTOCOMMIT)
cursor = connection.cursor()
cursor.execute("LISTEN channelxyz;")
connection.poll()
connection.commit()

I would like to "listen" to the listeners and process them further.

What I have stored in the database is from another system, I just want to wait for updates from the database and output them in the UI.

2

Several clients use psycopg (2) without ZPsycopgDA in Zope applications. Thus, this is possible. The ZPsycopgDA makes a Postgres connection available as a Zope "database adapter" object -- an object in the Zope object hierarchy configurable via the ZMI (the Zope Management Interface). In the early days of Zope, this was important: Zope applications were mostly created via the 'ZMI. Nowadays, Zope applications live mostly in Python code, managed in a code repository; the ZMI(andZPsycopgDA`) has lost much of its importance.

Keep in mind however, that Zope is a multi-task transactional system. It is likely that you want an integration of Postgres in Zope's transaction system and avoid that current threads use the same Postgres connection.

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