On Monday 30 October 2006 10:28, Rzepa, Henry wrote: > At 15:02 +0000 29/10/06, S Page wrote: > > >I wanted to define an attribute Smiles:=string, where the string could > > > contain > >> > >>quite a few characters (its more or less 1 character per atom in a > >>molecule, and > >>some molecules can easily have 1000+ atoms). Is there limit to how long > >>such a string could be? > > > >Yes, the Type:String code limits strings to 255. There's a warning in the > > factbox when you exceed this. It was discussed earlier, > > http://sourceforge.net/mailarchive/message.php?msg_id=36371763 ; although > > you could probably work around the MediaWiki limitations if you edit the > > PHP code and alter your database, there's a performance hit. > > > >Can you explain or link to the underlying property for "Smiles" that > > you're trying to represent, is it a chemical formula like NaCl? It's > > nice to understand what people are trying to do. >
<snip> > > I understand the reason for limiting an attribute to 256 characters. > Perhaps we should define an entirely new datatype (InChI) which > expands this limit (and put up with the performance hit?). Is > this a sensible approach? (we can think of a number of other chemical > datatypes; for example molecular formula). Having arbitrary long texts would be possible, given that one finds a suitable place to store them in the database. Currently, the normal text field is limited in length to enable indexing, and we would loose this for all attributes if some would need the maximum length to be changed. Now one could more or less easily use an auxiliary table to still manage the situation, where the original table contains a hash or a key or something to stay compatible with searching. I think this can be done, but I need to think about possible ramifications. And I think that the database will only change again in the release after the next one. -- Markus -- Markus Krötzsch Institute AIFB, University of Karlsruhe, D-76128 Karlsruhe [EMAIL PROTECTED] phone +49 (0)721 608 7362 www.aifb.uni-karlsruhe.de/WBS/ fax +49 (0)721 693 717
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