[Zope] Re: Versioned connectors from ZODB

2005-07-12 Thread Tres Seaver
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Tim Peters wrote:
 [Etienne Labuschagne]
 
I did get the versioned connections to work (so far), BUT, I will
definately take your word on it and seek another solution :)
 
 If that works for you, don't let nay-sayers scare you away.  I don't
 think there are any reports of version bugs open in the Zope collector
 at present -- but that could just mean that everyone stays away from
 them now.

The community has grown averse to using versions because they interact
poorly with content catalogs (by locking the individual BTree buckets in
the catalog's indexes).  If Etienne's need doesn't involve touching the
catalog, or if he can affort to do catalog-munging updates only within a
version, then versions will work as designed.

They are still a nice way to experiment with customizing ZPT, etc.
(which won't typically touch the catalog).


Tres.
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[Zope] Re: Versioned connectors from ZODB

2005-07-11 Thread Tres Seaver
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Etienne Labuschagne wrote:
 On 7/11/05, Florent Guillaume [EMAIL PROTECTED] wrote:
 
ZODB versions are deprecated, unsupported, buggy and hard to use. Don't
use them.

Florent
 
 
 And as I understand, so are temporary connections too.  That leaves me
 with getting a normal ZODB connection from the pool which I don't
 want to do.
 
 I really need a temporary connection that I can discard.  This
 connection can have a much smaller cache than the normal connections
 as it makes very little difference in the speed of data loading. 
 Second prize is a connection that will only be used by a specific
 process and never used for other processes.  Versions solves this for
 me.
 
 I can check out a connection and keep it aside only for data loading. 
 But this means that I waste precious memory on a connection that does
 not really need to cache the amount of objects that the other
 connections should.  In my case, this translates to using 1GB of RAM
 on one connection that gets used once a day.
 
 Please believe me that I really need a special connection.  For
 those who really want to know why, below is an attempt at an
 explanation why:
 
 In the application that I have written, I want to be able to get
 connections that are not part of the normal connection pool.  Once my
 process is finished, I can store these connections for later use, or
 discard them.  Currently my application uses the normal connections in
 the pool.  The problem is that this process contaminates the cache
 of the connections with objects that are not used in normal client
 application use (I use a thick client).  This means that the client
 applications are extremely slow the next day and that it takes a long
 time before the cache contains the often used objects again.
 
From there the reason why I DON'T want to use the connections for my
 once a day data loading process.
 
 My ZODB contains about 700`000 objects.  A connection caches about
 60`000 objects to give satisfactory client speed.  To start up the
 client before the cache is initialized, takes about 5 minutes.  Once
 the cache is populated, it takes a client seconds to start up.  Data
 loading invalidates all of this, but is worse than a clean cache in
 that it takes long for the new objects in the cache to be flushed
 and replaced by the often used objects again.  Data loading does not
 need such a big cache since it mostly loads data into the ZODB. 
 Unfortunately, the loaded objects also end up in the cache.
 
 Why do I need so many objects in the cache?  Some searches cannot be
 done with a mere ZCatalog search and have to run through a subset of
 all the objects.  These tend to fit nicely in the cache.

Your query would be better served on the zodb-dev list, where Tim Peters
hangs out;  he can probably explain how to get what you want without
guessing.  If I had to guess, I would suggest constructing your
connection programmatically, where you can specify the object cache size
for instance, and then closing / discarding the connection when you are
done.


Tres.
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Tres Seaver  +1 202-558-7113  [EMAIL PROTECTED]
Palladion Software   Excellence by Designhttp://palladion.com
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