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Liam, Thanks for your post. I like your pragmatic aproach ! Eric "Liam R. E. Quin" wrote: > > I've lost count of the number of systems I have seen storing SGML or XML > in a database. > > I have seen 3 basic approaches. Of these, one approach almost never > works, or if it does, dramatically increases sales of snacks and > coffee while people wait for a response when it's used. > > The approaches are > (1) decompose every element into a field in a relational or OO database. > With a relational database, this always seems to end up sad. > A wait of 30 seconds to a minute or more on half a million dollars > worth of server hardware is pathetic. > > (2) decompose down to paragraphs, but store mixed content as blobs. > much faster, for most people, but you lose the ability to find > things like embedded part numbers that might have been the reason > for using the database in the first place. > > (3) store documents in flat files. Use the database to manage them, > and to store metadata. Use external text retrieval. > Fast performance (sub-second response on a million-document > database with a middling SPARC server is plausible, or a few > seconds for a more complex text search). > > There are many varioations on these. It is possible to use an > object oriented database in such a way as to give good response, but > it is difficult. It's possible to get good response for a specific > application with a relational database too. But if you compare the > performance with Oracle (the market leader) with mySQL (free, does not > support transactions, rollback, cursors), you see that you are not > paying for performance. > > Marc Rochkind mentions [1] a database that did 40,000 or more transactions > per second on a PDP-11, but I doubt there was locking or rollback or > journalling. My own text retrieval packaeg can do several million > database operations a second, but again without locking. > > Luckily, you don't need locking and rollback below the "file" level > for most XML applications -- where "file" is the granularity at which > documents are saved and/or edited. > > If performance isn't a major issue, though, I agree that using te > database is often the simplest way. Some databases even support > searching of text fields and BLOBS these days, which makes it more > attractive. > > Don't underestimage grep, by the way -- I've seen a good version of > gerp search over 50 megabytes a second, on a fairly low-end > SPARC system (an SS10, you can't buy them that slow now). You won't > get that performance on a PC, usually, because the I/O just isn't > there, even with a SCSI PCI system, but it's coming. And two PCs > in parallel are less than half the price of a SPARC Ultra. > > You have to look at what staff you have. > > If you have Unix programmers, the grep solution may be a good one, > once you deal with normalising white-space. > > If you have SQL programmers, then any problem will seem to have a > solution involving a database :-) and that's the way to go. > > It's better to have a slow system that works, and that you can fix > and extend, than a super-duper quantum rocket-science thingy that > 99% works but no-one can do the last 1% unless you hire a wizard. > There _are_ no wizards, only people. > > The best solution is the one that works and can be supported in > your environment. > > Lee > > -- > Liam Quin, Barefoot Computing, Toronto; The barefoot agitator > l i a m q u i n at i n t e r l o g dot c o m > Ankh on irc.sorcery.net, ankle5/Ankle{MD} on DALnet > > XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list -- ------------------------------------------------------------------------ Eric van der Vlist Dyomedea http://www.dyomedea.com http://www.ducotede.com ------------------------------------------------------------------------ XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list
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