Well, then, that is quite a strange use case :-) Nevermind my simple methods. Malcom's suggestion of an extension for postgres seems like a good idea--writing functions in various languages (like Python!) is _really_ easy in postgres.
Just out of curiosity (for either of you,) what is a search like that used for? I've had a lot of strange requests from a lot of (generally strange) clients, but that's a pretty weird one. On Mar 5, 12:14 am, koranthala <koranth...@gmail.com> wrote: > Thank you very much Jeff and Malcolm for the extremely helpful > replies. > Jeff, the substring match is not based on spaces. Rather, the string > can start anywhere and end anywhere. > So, I cannot think of a way to do it, as Malcolm said. > I had also done the same thing as Malcolm, i.e. pulled every tuple to > memory (luckily I dont expect more than 200 odd tuples for this > particular scenario) and am comparing individually - except for the > fact that I was stopping at the first substring match. - I guess I > should be doing the "longest common substring" as Malcolm mentioned. > Again, thank you Jeff and Malcolm. > > On Mar 5, 6:18 am, Malcolm Tredinnick <malc...@pointy-stick.com> > wrote: > > > On Wed, 2009-03-04 at 05:01 -0800,koranthalawrote: > > > Hi, > > > How do I implement a substring query? > > > Please find the example below. > > > From Django Documentation: > > > Entry.objects.get(headline__icontains='Lennon') > > > => This matches the headline 'Today lennon honoured' > > > > My query is the opposite: > > > I have the string 'Lennon' inside my DB, and I have to match 'Today > > > Lennon honoured' > > > Say: > > > Entry.objects.get(headline__isubstring='Today Lennon Honoured') > > > should return headline 'Lennon'. > > > > I checked iregex too, but I cannot seem to solve it myself. If > > > somebody has solved this, could you please help me out. > > > This isn't the type of searching operating that is going to be standard > > outside of specialised packages. It's actually a really hard problem > > (not impossible, there are solutions, but hard) in general. The > > complexity comes from the fact that the match could start anywhere and > > involve any number of characters. So to do this efficiently requires > > some special datastructures (with suffix trees and some other > > structures, you can the search in about O(total length of text)). > > > Now, I'm sure it wouldn't be impossible to write, say, an extension for, > > say, PostgreSQL (picking that database because of its excellent support > > for extensions) that supported this kind of searching, but it would be a > > fair bit of work. It would require a particular sort of index structure > > to support the searches. I don't know any package off the top of my head > > that does this for databases. Might be a fun project for somebody with a > > bit of time and curiosity. > > > I've done this kind of thing in the past for a couple of clients and > > I've always pulled the text to be searched into memory. Create a data > > structure of all the headlines to be searched (using your example) and > > then match the search string against them to find the longest common > > substring match. There's a lot of literature on this sort of stuff, and > > searching for things like "longest common substring" will give you a > > place to start. > > > Regards, > > Malcolm > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-users@googlegroups.com To unsubscribe from this group, send email to django-users+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/django-users?hl=en -~----------~----~----~----~------~----~------~--~---
