On Thu, 17 Apr 2008 02:48:37 +0200, Stephen Denne
<[EMAIL PROTECTED]> wrote:
PFC wrote:
Let's try this quick & dirty implementation of a local
count-delta cache
using a local in-memory hashtable (ie. {}).
CREATE OR REPLACE FUNCTION update_count( key TEXT, delta INTEGER )
RETURNS INTEGER
AS $$
if key in GD:
GD[key] += delta
else:
GD[key] = delta
return GD[key]
$$ LANGUAGE plpythonu;
Thanks for the code, this seems to be very much what I was looking for.
I don't know plpythonu (nor python), just read a few docs now:
Learn Python, it is a really useful language ;)
"The global dictionary SD is available to store data between function
calls. This variable is private static data. The global dictionary GD is
public data, available to all Python functions within a session. Use
with care."
Does session == transaction or connection?
I don't understand the difference between SD and GD, private and public.
Where are the context boundaries?
There is no sharing between processes, so
- both SD and GD are limited to the current session (connection, postgres
process), no shared memory is involved
- GD is global between all python functions (global)
- SD is specific to each python function (static)
The big gotcha is that these are all non-transactional : if you rollback,
GD and SD stay the same, and when you issue a query, you can assume the
state of SD and GD is random (due to previous queries) unless you
initialize them to a known value.
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