Oh dear, first it's nice of Michael to send a reply. But can any of you Digital Creations people see what the problem with the answer? Well before I go critcising it, first let me say I'll have some off-list discussion with Michael to see if I can get the sort of documentation going we need. But (and I'm sorry Michael to be picking on you - I KNOW its not you fault) what those "giving up in frustration" people are talking about is the fact that there is NO answer here(as is often the case in other replies/documentation - obviously NOT written by Michael by the way). This reply tells me how great ZCatalogue is(how fast etc. etc.) and how I can work with ZClasses(if I design them "right"). In effect this is a piece of either developer enthusiasm(always good to see) or marketing blurb(and if your frustrated already you can easily pick this option - I'm choosing not to by the way). So what this doesn't do is tell me how to search Zope objects by attribute value, which was the question I asked. It is in turns too much information and too little. So what I want to see is a simple piece of code that lets me search my Zope database where I can, as a complete novice, substitute my objects and my attributes to get back a list of things I can itterate over. Lets ignore perfomance, b-tree's, ZClass design etc. etc. Assume I have NOT installed ZCatalogue(unless of course it comes by default on my NT Zope 2.0 install, does it?), and I'm using DTML Documents. In short assume I am an idiot(you wont be so far wrong) but I need to get something working pretty quickly, and I'll make it graceful later. OK now the specifics are out of the way I want to quickly offer up a view on why we need to stop the development process(or slow it down severely) and address the documentation issue. In a word "SPECTRA". This is the new content management tool from Allaire, based on their ColdFusion web/database interface. Recently Allaire were out here doing demo's and training, we were invited, and attended. So basically it's in the same domain as Zope and it's VERY powerful. It will not by the way be the last product in this domain, but right now it's shaping up to be the competition for Zope. Now I don't really mind if Digital Creations don't think it is the competition, it is as far as potential customers are concerned(well the potential customer I work for anyway). The good news is that it's about Aus$12,000 per copy and wont really be ready for prime time for about 8-12 months(we think). The bad news is that it WILL ship with VERY VERY good documentation. In fact the ticket price isn't such a differentiator either; anyone (including you guys at DC) who thinks Zope is free is really fooling themseleves, ticket price is but one(small) component in the overall cost of software, poor documentation is another soaring cost to organisations such as ours. So the only real advantage left is the 8-12 months window, which we need to use for documentation. Now we might all think Zope and the python/OO technologies around it as well as its inherent design, flexibility, extensibleness means we have a better product here, and that only a deluded fool would use a relational based blah, blah, blah product. But the reality is that Allaire will beat us out here(they have a lot of experience with volume delivery) if we don't meet them on MANDETORY issues like good documentation. We have an opportunity to keep this area of our industry open, with the use of Zope. But it will pass us by if we dont get good documentation soon. This is but one of a range of arguments made here for getting on the documentation-for-dummies bandwagon. Phew that got really long, sorry to take so much of your time. Lindon
And whilst we're here if you'll tell me how to search through all the Zope objects in my site by some attribute and then display some (other) attributes, basically like a SELECT statement but not on a database instead on Zope itself(see I'm really new) I'll write that FAQ/chapter too...
Well there is, of course, more than one way to skin this cat. Before Zope 2.0, there was the find machinery, which would brute force search through your objects looking for ones that matched certain criteria. This is, of course, not very efficient for the same reasons that full text indexers don't use command line tools like 'find' and 'grep'. They are good one time use tools, but not efficient for lots of searching.
Zope 2.0 introduces ZCatalog. ZCatalog is a very flexible and powerful tool, and thus, probably requires lots of documentation.
ZCatalog works one of two ways, first, you can use the aformentioned 'Find' machinery to find objects on your Zope and 'catalog' them. This means that if a found object has an attribute your looking for, the value of this attribute is stored in the catalog is a very fast BTree like data structure. By fast, I mean less than a second to find one out of a million cataloged objects (my book on BTree theory says that average case it takes only 20 simple comparison operations to find one out of one million items, so it's probably a lot less than one second).
The tradeoff is speed for memory and database consuption. Since the catalog is storing lots of information about the object, such as references to its values and such, ZCatalog can bloat your database/memory footprint.
The second way ZCatalog works is trasparently with ZClasses. If you design your ZClasses right, they can automaticly catalog and uncatalog themselves as they are created, destroyed, edited, and moved around Zope. This is wildly useful for things like News items. If you create your own 'News' ZClass that properly catalogs itself, you can create a fully text searchable News system with little maitenance overhead.
Oh did I mention ZCatalog can fully text search? That's right, one of the indexes ZCatalog can create are 'TextIndexes'.
Thankfully ZCatalog comes out of the box fairly well preconfigured for Zope. Granted, you must add any additional attributes you want to find that don't come stock, but be default ZCatalog will index id, creation time and meta_type, and text index title and text content (if there is any).
Note that ZCatalog does *not* create search forms for you. But a good template form and report document can be generated by the 'Z Search Interface' wizard by selecting 'Add: ZSearch Interface' in Zope and selecting the Catalog you wish to point the search form to. You can have as many types of search forms as you please.
There will be *many* upcomming usage examples in the new zope site, which uses the Catalog extensivly on almost every page.
-Michel
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