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Re: Storing large strings for future equality checks

Cross-posted to 3 groups.

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On Jun 8, 9:35 am, Abu Yahya <abu_ya...@invalid.com> wrote:
> A small application that I'm making requires me to store very long
> strings (>1000 characters) in a database.
>
> I will need to use these strings later to compare for equality to
> incoming strings from another application. I will also want to add some
> of the incoming strings to the storage, if they meet certain criteria.
>
> For my application, I get a feeling that storing these strings in my
> table will be a waste of space, and will impact performance due to
> retrieval and storage times, as well as comparison times.
>
> I considered using an SHA-512 hash of these strings and storing them in
> the database. However, while these will save on storage space, it will
> take time to do the hashing before comparing an incoming string. So I'm
> still wasting time. (Collisions due to hashing will not be a problem,
> since an occasional false positive will not be fatal for my application).
>
> What would be the best approach?

If it's that relevant that you're asking, measure first to see if it's
a problem. If you're that concerned that it will be, then code a
number of reasonable alternatives and measure.

Presumably you need to do a Map lookup on the incoming strings. I
thought about some itern scheme, but that won't work if you're
receiving a lot of incoming new strings. Storing hashs could work. Do
you need to store the strings in a database? If you can store them
locally, maybe a trie?
http://en.wikipedia.org/wiki/Trie
I somewhat doubt (maybe?) that you're going to get much better lookup
performance than a trie (but of course I would measure too).

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Thread

Storing large strings for future equality checks Abu Yahya <abu_yahya@invalid.com> - 2011-06-08 22:05 +0530
  Re: Storing large strings for future equality checks markspace <-@.> - 2011-06-08 09:49 -0700
    Re: Storing large strings for future equality checks Willem <willem@toad.stack.nl> - 2011-06-08 17:28 +0000
      Re: Storing large strings for future equality checks Abu Yahya <abu_yahya@invalid.com> - 2011-06-08 23:45 +0530
    Re: Storing large strings for future equality checks Abu Yahya <abu_yahya@invalid.com> - 2011-06-08 23:45 +0530
  Re: Storing large strings for future equality checks David Kerber <dkerber@WarrenRogersAssociates.invalid> - 2011-06-08 12:58 -0400
    Re: Storing large strings for future equality checks Abu Yahya <abu_yahya@invalid.com> - 2011-06-08 23:49 +0530
    Re: Storing large strings for future equality checks Lothar Kimmeringer <news200709@kimmeringer.de> - 2011-06-08 20:31 +0200
      Re: Storing large strings for future equality checks Harry Tuttle <OTPXDAJCSJVU@spammotel.com> - 2011-06-09 10:50 +0200
        Re: Storing large strings for future equality checks bugbear <bugbear@trim_papermule.co.uk_trim> - 2011-06-09 11:44 +0100
      Re: Storing large strings for future equality checks Harry Tuttle <OTPXDAJCSJVU@spammotel.com> - 2011-06-10 10:15 +0200
  Re: Storing large strings for future equality checks Gene Wirchenko <genew@ocis.net> - 2011-06-08 11:07 -0700
    Re: Storing large strings for future equality checks Abu Yahya <abu_yahya@invalid.com> - 2011-06-08 23:58 +0530
    Re: Storing large strings for future equality checks Hallvard B Furuseth <h.b.furuseth@usit.uio.no> - 2011-06-09 12:38 +0200
    Re: Storing large strings for future equality checks Michael Wojcik <mwojcik@newsguy.com> - 2011-06-09 17:32 -0400
      Re: Storing large strings for future equality checks bugbear <bugbear@trim_papermule.co.uk_trim> - 2011-06-10 10:51 +0100
  Re: Storing large strings for future equality checks Lothar Kimmeringer <news200709@kimmeringer.de> - 2011-06-08 20:28 +0200
    Re: Storing large strings for future equality checks Martin Gregorie <martin@address-in-sig.invalid> - 2011-06-08 22:02 +0000
  Re: Storing large strings for future equality checks rossum <rossum48@coldmail.com> - 2011-06-08 21:38 +0100
  Re: Storing large strings for future equality checks Robert Klemme <shortcutter@googlemail.com> - 2011-06-08 23:20 +0200
  Re: Storing large strings for future equality checks Tom Anderson <twic@urchin.earth.li> - 2011-06-08 23:02 +0100
  Re: Storing large strings for future equality checks Joshua Maurice <joshuamaurice@gmail.com> - 2011-06-09 15:01 -0700

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