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Concurrency/Atomicity in ZSQL/ZOracleDA ?
by Renaud Guerin 25 Mar '02

25 Mar '02

Hello, I have a probably simple question, but got different opinions on the matter, and I'm seriously in need of a quick answer. I need to make a ZSQL method that inserts data in a table this way: 1) first, generate a new ID with something like SELECT MAX(ID)+1 AS my_id FROM ... (using a sequence is not an option for me for various reasons) 2) then, INSERT with the ID previously generated ( is INSERT INTO ... VALUES (<dtml-var my_id>.... the right way to do this ?) 3) display my_id to the user for future reference. First, I'm not sure how to do 3) : how do I pass my_id back to the original DTML document (which calls the ZSQL method with dtml-call) ? Also (main question), is there something particular to do to ensure SELECT+INSERT is done in an atomic way that avoids concurrency problems ? I know Zope starts and ends transactions with HTTP requests, but I'm not sure this implies the kind of read locking I need. thanks a lot! PS: please cc any answers.

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Re: [Zope3-dev] a note on groups and roles
by Lennart Regebro 25 Mar '02

25 Mar '02

From: "Chris McDonough" <chrism(a)zope.com> > and not with users. Additionally, this set of ideas obviates the need > for "local roles" because users and groups are *always* defined in a > place. Adding a group and associating permissions with the group to the > place represented by the root container or to an individual leaf object > twelve levels deep actually becomes the same operation. I dont' understand this part at all. Either it is possible to have different permissions in different places, or it's not. With a roles system, this is done by giving people roles locally. If you scrap the roles, then it means you either have to assign people to groups locally, ie local groups, or you must be able to set the permissions locally, ie local permissions. So your suggestion doesn't obviate the need for local roles, it just creates a need for something other that is local, since you don't have any roles at all, and therefore obviously can't have local roles. :-) I any case: There are a lot of permissions in a Zope system. When adding some more products, you get even more permissions. Roles are a grouping of permissions, and is neccessary to make the permission system mangeable. If you each time you need to locally change the permission settings for a group of a person have to wade through 30-40 permissions and remember exactly what each of them does, you will only end up with giving most people the rights to do almost everything. The only problem with the Roles system is that people over and over again mistake it for usergroups, since they are expecting usergroups. This can be fixed by having some type of usergroups in addition to the roles. Then people won't think roles are usergroups, read the documentation and see the light. Besides, some type of user grouping is necessary. Also, the Anonymous and Authorized roles should be removed, because these are not proper roles, and may add to the confusion of roles and groups. Anonymous should be a built-in and non-removable principal. If it helps to clear up the roles concept, maybe some other roles like "Author", "Viewer" or "Member" should be created by default. But "Authorized" is a state, not a role. > FWIW, relatedly, I don't understand the use of the term "principal" > instead of "user" for the "entity with credentials" in Zope 3. Neither do I. For me "principal" means "headmaster". :-)

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Design data-storage / search
by Antwan Reijnen 25 Mar '02

25 Mar '02

Hi all, I have a design question. I'm using the CMF, but my questions are not specific for CMF, so I post it in this generic group. I want to construct a CMF content object, which contains a questionary of about 50 questions. Some require a free-text answer, others are multiple-response- or singe-response answers. Sometimes a combination is used ("please enter your motiviation here"). The answers of this questionary should be searchable. The standard way (?) that comes to my mind is to construct a portal_catalog with a rather large index of more than 50 keys. But I'm wondering if this is the optimal solution for this kind of data. Should I use a database or another kind of datastorage for these kind of data-structures? Tinytables? Maybe I should construct a special catalog for this, so the portal_catalog does not become inefficient? Any thoughts and experience on this kind of subject is highly appreciated. Thanks in advance, greetings, Antwan. Antwan Reijnen DEXUS New Media Metropole Office Laan van Meerdervoort 70 2517 AN Den Haag Tel 070-3114800 Fax 070-3656279 http://www.dexus.nl DEXUS New Media maakt deel uit van de Metropole IT Group http://www.metropole-it.nl ICQ#: 7916222

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How to upload files and create file objects from DTML page?
by Mark Spencer 25 Mar '02

25 Mar '02

I want to have a normal DTML page for users that allows them to upload and download files (without needing to use the management interface). The downloading and display of files is fine, but I cant figure out the zope/python code to create a new file object and store an uploaded file. The files could be upto ~60MB in size, and can be zip or doc files etc. Has anyone seen suitable sample code for this?

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approach for persistent global links - is this good?
by Jens Wolk 25 Mar '02

25 Mar '02

Salut everybody, in a yellow pages ("zyp") product I need pointers or links between objects. For example I have categories and links to categories. It is necessary, that such a link to a category is still valid after having moved the category; this is why storing away the path isn't applicable. As of now, Zope doesn't provide a global id one can work with. (For a discussion about this issue and possible solutions in the future, see http://dev.zope.org/Wikis/DevSite/Proposals/ObjectHub ) I found a solution which seems to work fine for me: each category gets an attribute called "zid". This zid is globally unique. (Based on a mechanism presented by alex.khan http://dev.zope.org/Members/alex.khan/GlobalSystemId ) Storing a link is as easy as storing the zid of the linked category. However, the lookup of a linked category is done by a lookup in a ZCatalog with an appropriate field index. What do you think about this? This might not be such a good idea in terms of performance. Your comments are very welcome Jens Wolk

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Unique object Ids
by Tom Cameron 25 Mar '02

25 Mar '02

When I try to render an object I often get something like '<Model instance at 02620E00>' This suggests to me that this object has some kind of unique ID 02620E00 that identifies this particular instance. Is there any way that I can query an object to find this id? My aim is to find some way to uniquely identify all objects so that I can find them later without having to store their entire path. Tom

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form with mutiple actions?
by Hamzal Kamal 25 Mar '02

25 Mar '02

Hi, Is it possible for form to have more than one actions? What i have in mind to do is to collect some user info through the form and store them into table at the same time display this info in another form for the user to enter the remaining info and then finaly pass the info into secure form. Any idea on the matter will be appreciated. ===== Hamzat kamaldeen Ishola Dnet Systems Limited 223 Ikorodu Road, Lagos. 234 1 7749381, 234 08033011305 __________________________________________________ Do You Yahoo!? Yahoo! Movies - coverage of the 74th Academy Awards� http://movies.yahoo.com/

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Security and document library product
by D.Turpie＠open.ac.uk 25 Mar '02

25 Mar '02

Hi there I am currently implementing the document library product on Zope/CMF and have a security question. I have a number of different types of users who should have differing access to the Document Library. There are anonymous users, content authors and content managers. I would want anyone (anonymous or otherwise) to be able to look at, search and browse the library and I have achieved this. I would want the authors to also be able to submit documents and this I can also get working At a third level I would like content managers to be able to review submitted documents but can't seem to implement this level of security. I have followed the Document Library documentation and set-up the security as it says but this still doesn't seem to give content managers the right to review. Probably something I am or am not doing. Any help, ideas gratefully received. Thanks. David.

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sequence.sort: how can I sort strings?
by Danny Adair 25 Mar '02

25 Mar '02

Hi! How can I sort a sequence of STRINGS using sequence.sort? I don't know what to use as a "key"... (I tried self, str, value, '', _.None, ....... :-)) Or in other words: What's the attribute of a string that returns the string itself? thanks, Danny

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Where is Oracle ZODB storage ? Large file support in NT 4 ?
by Jean-François Ménard 25 Mar '02

25 Mar '02

I would like to move my ZODB to a DBMS (probably Oracle) Goals: - Get around the 2 gigs limit in NT4. - Speed up data access. Questions: - Where can I find Oracle ZODB Storage ? - Where could I find compiled Python with enabled larges files support ? - How can I speed up data access in a large ZODB ? Can ZEO speed things up if only used on one multiple processors server ? Ho, one final thing... ZOPE really rock !!!! :)) Jeff

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