March 2000 - Zope - Zope lists

ANN: ZEO goes Open Source
by Jerry Spicklemire 22 Mar '00

22 Mar '00

Open Source, Scalable, 24x7, Unstoppable!

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RE: [Zope] Sybase: How generate id keys? (surrogate keys)
by Alexander Staubo 22 Mar '00

22 Mar '00

I use identity columns with Sybase -- the only problem I've experienced is a tendency to occasionally "burn" ID values, resulting in gaps. If you're not worried about non-sequentiality, identity columns are generally not a problem. Do you anticipate crashes? I have run Sybase for about a year, and never experienced a single crash -- meanwhile, Zope has crashed and/or been restarted many, many times. Aside for identity columns, here's an alternative scheme I used some time ago with an Access database (where, aside from DAO/ADO, you simply cannot obtain the previously inserted "autoincrement" value, causing problems for web-based forms): Create a table such as this create table Ids ( Id int not null primary key nonclustered ) Then create either a stored procedure (don't like 'em) or a Zope DTML Method that will (a) get the lowest available ID, and (b) if the table is getting empty (count < delta), then replenish the table with new, unique values, starting at the ID you just obtained. (If the table is empty when you start out, assume this is the first time the method is run, and simply start with a seed of, say, 1.) Because of transaction logic, IDs will never be "burned", and the only gaps you will experience will come from IDs that disappear when their parent records are deleted. Hope this helps. -- Alexander Staubo http://alex.mop.no/ The difference between theory and practice is that, in theory, there is no difference between theory and practice. > -----Original Message----- > From: Hung Jung Lu [mailto:hungjunglu@hotmail.com] > Sent: Tuesday, March 21, 2000 12:24 AM > To: zope(a)zope.org > Subject: [Zope] Sybase: How generate id keys? (surrogate keys) > > > Hi, > > How do people generate id keys (surrogate primary keys) > in Sybase+Zope? There are some recommended ways of doing it > in Sybase with stored procedures but I can't run stored > procedures in Sybase. > > I am looking at heavy-traffic strategies. So I need something > slightly better than a simple increment table for the keys. > > Any recommendations? Thanks in advance. > > Hung Jung > > ______________________________________________________ > Get Your Private, Free Email at http://www.hotmail.com > > > _______________________________________________ > Zope maillist - Zope(a)zope.org > http://lists.zope.org/mailman/listinfo/zope > ** No cross posts or HTML encoding! ** > (Related lists - > http://lists.zope.org/mailman/listinfo/zope-announce > http://lists.zope.org/mailman/listinfo/zope-dev ) >

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RE : [Zope] Sybase: How generate id keys? (surrogate keys)
by Sin Hang Kin 22 Mar '00

22 Mar '00

The unique id problem come up again and again. The automatically generated unique id will benefit web author with sql row id object id and may be some others With a view that zope will be run over the network with distributed storage across the net, I would like to suggest we implement a unique id server which can be a zope server serving on another port and serialize all request and return the globally unique id. Does this work? I also suggest zope can be configured to automatically get the object id from this service and have globally unique object ids. Rgs, Kent Sin

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RE: [Zope] Casting to a list
by Daniel.Weber＠SEMATECH.Org 22 Mar '00

22 Mar '00

Ihis didn't work, then? Looks better than what I came up with, which, for the list vs. string situation goes like: <dtml-try> <dtml-in string_or_list_var> list stuff... </dtml-in> <dtml-except> non-list stuff... </dtml-try> If you have a string with multiple values to split, use the _.string.split() function, as... <dtml-in "_.string.split(str [,separator])"> This will probably choke on lists, though. Combine the two for a wholesome, good-start-to-your day breakfast code. :-) > -----Original Message----- > From: Ken Kinder [mailto:kkinder@messagemedia.com] > Sent: Wednesday, March 22, 2000 12:31 PM > To: zope(a)zope.org > Subject: [Zope] Casting to a list > > > Another question (soon I'll start answering more on this list :) - I > have a set of checkboxes with the same name that I iterate through > using dtml-in. However, when only one checkbox is checked, dtml-in > complains that a string cannot be used as input, it expects a > sequence. My initial thought was to do this: > > <dtml-if "type(var) == type('')"> > ... (do not iterate) > <dtml-else> > <dtml-in var> > ... > </dtml-in> > </dtml-if> > > How can I either cast a string to a list w/o messing up an existing > list, or gain access to Python functions such as type() from a > dtml-if statement? > > -- > Ken Kinder > 303.381.7631 > > _______________________________________________ > Zope maillist - Zope(a)zope.org > http://lists.zope.org/mailman/listinfo/zope > ** No cross posts or HTML encoding! ** > (Related lists - > http://lists.zope.org/mailman/listinfo/zope-announce > http://lists.zope.org/mailman/listinfo/zope-dev ) >

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cannot modify security for a file object
by sathya 22 Mar '00

22 Mar '00

I get the following error when trying to modify security for a file objest. Any ideas why ?. I am using 2.1.4 and the file is a pdf doc Thanks ------------------------------ Zope Error Zope has encountered an error while publishing this resource. Error Type: AttributeError Error Value: tag Troubleshooting Suggestions The URL may be incorrect. The parameters passed to this resource may be incorrect. A resource that this resource relies on may be encountering an error. For more detailed information about the error, please refer to the HTML source for this page. If the error persists please contact the site maintainer. Thank you for your patience. -- ########################## necessity is the mother of invention ##########################

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Re: [Zope] Sybase: How generate id keys? (surrogate keys)
by Hung Jung Lu 22 Mar '00

22 Mar '00

bill anderson <bil-(a)libc.org> wrote: >IOW, would a random, unique id work for you? Yes, it'll be fine. >http://www.zope.org/Members/Bill/Documentation/AutoGenID Thanks. That is the current work-around that I am using... (Key derived from a time-stamp with millisecond precision.) There is one observation and two problems: (1) ZopeTime is not as good as the getdate() function from Sybase, if you are running multiple Zope webservers (for load-balancing.) That is, it's better to rely on one unique source of timer. (2) There is a slight chance of two processes getting the same key, if they happen to occur within one millisecond of each other. The probability is small, but unfortunately I have to address even this minuscule probability. :( (3) If the server's time is re-adjusted for any reason, it's possible that some keys are regenerated. I agree that the millisecond-precision key is really good for non-critical applications. But because of the nature of our project, we need to address even the slightest chance of error. :( I think I will adapt the Sybase's recommended stored procedure to Zope, by using DTML and ZSQL methods. It's kind of nasty for something as simple as a surrogate key generation, but it seems more secure. thanks again, Hung Jung ______________________________________________________ Get Your Private, Free Email at http://www.hotmail.com

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Casting to a list
by Ken Kinder 22 Mar '00

22 Mar '00

Another question (soon I'll start answering more on this list :) - I have a set of checkboxes with the same name that I iterate through using dtml-in. However, when only one checkbox is checked, dtml-in complains that a string cannot be used as input, it expects a sequence. My initial thought was to do this: <dtml-if "type(var) == type('')"> ... (do not iterate) <dtml-else> <dtml-in var> ... </dtml-in> </dtml-if> How can I either cast a string to a list w/o messing up an existing list, or gain access to Python functions such as type() from a dtml-if statement? -- Ken Kinder 303.381.7631

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[ZGotW] Issue #7 (Closed)
by Zope Guru of the Week 22 Mar '00

22 Mar '00

The current issue of "Zope Guru of the Week" has closed: =================================================================== Issue #7 -- To ZClass or not to ZClass? =================================================================== Status: Closed Zen Level: Chela (4/8) Keywords: ZClasses Submitted by: Tres Seaver tseaver(a)palladion.com ------------------------------------------------------------------- When building a Product using ZClasses, I often want to create a "root" ZClass, which the manager will create in a normal folder, and which will then expose the Product's other ZClasses in its Add list. The DTML methods for the root are thus defined within this root ZClass. The Product ends up looking like:: Control Panel +- FooProduct + FooItem_add_permission +-FooRoot +- FooItem +- FooItem_add +- FooItem_addForm +- FooItem_factory .... +- index_html +- some_root_method_dtml + FooRoot_add + FooRoot_addForm + FooRoot_Factory + FooRoot_add_permission * What are the drawbacks to this approach? * Suggest alternatives. ------------------------------------------------------------------- Reviewed by: Tres Seaver tseaver(a)palladion.com ------------------------------------------------------------------- Hmmm, I don't seem to be doing so well on picking topics. Here is what I had in mind: * This site is an instance of the "ZGotW product":http://www.zope.org/Members/tseaver/ZGotW, which has a "main" factory, ZGotWRoot_factory, in its root folder. * This factory does *not* create an instance of a "folderish" ZClass, but rather, creates a normal Folder and populates it from a set of default DTML objects, along with a ZCatalog. * Individual issues of ZGotW are created within this folder as instances of the ZClass, ZGotWIssue, using the code in those "cloned" DTML objects. My rationale for adopting this approach, rather than creating a "folderish" ZClass, was to allow each instance of the "root" to be independently customized; the "common" behavior of a ZGotW site is included in a set of utility methods, which can be tweaked to enforce different policies, or change the look-and-feel of a particular site. The downside to this choice is duplication of code: should I find a bug in the original, default code, I have to then fix it in each instance as well as the Product. Comments, anyone? -------------------------------------------------------------------

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RE: [Zope] PHP vs Zope
by Alessandro Bottoni 22 Mar '00

22 Mar '00

Python is quite slanted toward this kind of applications: 1) very clear sintax (many webmasters are not particularly fond of C and Perl, like me...) 2) strong support for string management and a very good regular expressions module 3) wide choice of modules for interfacing with web servers, mail servers, database, etc... 4) ready-to-use modules for HMTL, Mail messages and XML manipulation 5) tons of good documentation, examples and a very active community 6) hard-rock core system and reliable modules 7) indipendence from the platform (Python runs almost everywhere. I'm re-compiling it for my Z80-based microwave oven...;-) Despite this, I think that the real reason why they decided to use python was the terror to commit a mortal sin (like touching a Perl interpreter) and the desire to live immersed in the light of the true Faith. I would have done the same... ---------------------------------------------------------------- Alessandro Bottoni (Alessandro.Bottoni(a)Think3.com) Web Programmer @ Think3 inc. (www.think3.com) I do not speak for think3 and they return the favour > -----Original Message----- > From: Nikolai Vladychevski [SMTP:niko@netspace.com.mx] > Sent: Wednesday, March 22, 2000 4:21 PM > To: Eric W. Sink > Cc: zope(a)zope.org > Subject: Re: [Zope] PHP vs Zope > > Very intersting stuff ... I think I will need finaly to try Zope my self > to see how it is. But I have one more question, why they decided to base > Zope on Python and not other language? > >

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Re: [Zope] Weird ZSQL Method thing...
by Tres Seaver 22 Mar '00

22 Mar '00

Rik Hoekstra <rik.hoekstra(a)inghist.nl> wrote: > > Jonothan Farr wrote: > > > > > Um, more or less (apart from the quotes). The ZSQL Methods use namespace > > > different from than normal DTML documents/methods (though I don't > > > exactly know how). Therefore you have to call them explicitly with an > > > argument. > > > > Sometimes you do, sometimes you don't. I know that sometimes I can acquire > > ZSQL method parameters from the request. Sometimes I have to provide them > > explicitly. > > I haven't been able to figure out what the rules are, either. If anyone out > > there could explain this behavior I'm sure lots of us would be grateful. > > > > Hm, I _think_ I recall (but I can't test this right now) that the ZSQL > method will only accept values that are given explicitly in its > arguments and in that case it will also acquire them. That would make > sense from a security point of view. > Or perhaps it was a bit more complicated - I have to investigate this I think the best analogy is to think of ZSQLMethods, ExternalMethods, and PythonMethods like "normal" functions in C: they receive information via arguments, and acquisition is always done via one of the explicitly-passed arguments. DTMLMethods/Documents are in some ways more like C macros: they grab information from the surrounding DTML context, without having to be told what they can "see". The analogy breaks down at the "call site": Zope looks at the explicit parameter lists and tries hard to match arguments to any parameters which are not explicitly passed by the caller: normally, it does this by looking them up in the REQUEST object, *not* in the current DTML namespace. Therefore, whenever calling a non-DTML method (External/Python/ZSQL/...): * poke all interesting values into the REQUEST object before calling:: <dtml-comment> calling 'foo( bar, baz )' </dtml-comment> <dtml-call "REQUEST.update( { 'bar' : 42, 'baz' : 3.1415926 } )"> <dtml-var foo> This version has the advantage of avoiding the "expression" syntax of DTML, but does require polluting the REQUEST namespace (may be an actual advantage if multiple methods use the same values). * pass the values explicitly, using positional arguments:: <dtml-comment> calling 'foo( bar, baz )' </dtml-comment> <dtml-var "foo( 42, 3.1415926 )"> This version looks most "natural" to a programmer, but is fragile WRT changes in the parameter list (changing the order of parameters on the method silently breaks this call). * pass the values explicitly, using keyword arguments for clarity:: <dtml-comment> calling 'foo( bar, baz )' </dtml-comment> <dtml-var "foo( bar=42, baz=3.1415926 )"> This version, which I prefer for any method taking more than one argument, says explicitly what it is doing, and therefore eases maintenance. Tres. -- ========================================================= Tres Seaver tseaver(a)palladion.com 713-523-6582 Palladion Software http://www.palladion.com

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