Theory&Practical Wildcard searches in DB quest?mlml

Theory&Practical Wildcard searches in DB quest?mlml

Post by Michel L » Sun, 14 Jul 1996 04:00:00



Hi All,

I've a task to do,
to search a huge DB column with wildcards, the difficulty is
that the wildcard chould be the 1st character.
e.g. search for "*ello*funny*"

The databasse is in CODEBASE(xbase), and there isn't a function to do that.
So, I've been trying to do it myself.
I've been looking at some search engines in the WEB and
i find all the engines require at least 1 character at the start of
the search criteria!
I'm pretty sure there must be some theory/practical way of
doing this .
can you please direct me to a book or web site etc....

thank you for yr help,
cheers
mike

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Theory&Practical Wildcard searches in DB quest?mlml

Post by Nigel McFarlan » Mon, 15 Jul 1996 04:00:00



> Hi All,

> I've a task to do,
> to search a huge DB column with wildcards, the difficulty is
> that the wildcard chould be the 1st character.
> e.g. search for "*ello*funny*"

   The problem you're having here is that large sets of data are usually
   indexed, and indexes usually imply some degree of ordering for
algorithmic
   performance. You're not supplying the beginning, end (or even middle)
of
   the data items to be matched against the ordering in the example you
quote.

   That said, you might consider the tool 'glimpse' available at
   <ftp://cs.arizona.edu/glimpse/glimpse-3.0.src.tar.Z>. This tool runs
in
   batch (usually overnight) and creates an index(outside any existing
database)
   which can be used with some pattern matching and in any event runs
   very fast so that multiple uses aren't bad performance-wise.

   However you have to compile it youself, etc, unless you're on a Sun.

    - Nigel.

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                  Melbourne, Victoria, Australia.         GMT +10 or +11 hours

   When was the last time you were that frustrated _away_ from a
computer?

 
 
 

Theory&Practical Wildcard searches in DB quest?mlml

Post by Chuck Schuel » Wed, 17 Jul 1996 04:00:00


Why not flip the data in redundant column and search that

*ello *funny
becomes
ynnuf* olle*

not perfect but it may help?


>Hi All,
>I've a task to do,
>to search a huge DB column with wildcards, the difficulty is
>that the wildcard chould be the 1st character.
>e.g. search for "*ello*funny*"
>The databasse is in CODEBASE(xbase), and there isn't a function to do that.
>So, I've been trying to do it myself.
>I've been looking at some search engines in the WEB and
>i find all the engines require at least 1 character at the start of
>the search criteria!
>I'm pretty sure there must be some theory/practical way of
>doing this .
>can you please direct me to a book or web site etc....
>thank you for yr help,
>cheers
>mike
>--
>    /-----------------------------------------------/ \--\--\  \-- \--
>   /                                               /---\  \  \ \\   \

> /-----------------------------------------------/                    

 
 
 

Theory&Practical Wildcard searches in DB quest?mlml

Post by Luis Jesús Colorado Nate » Thu, 18 Jul 1996 04:00:00



> Hi All,

> I've a task to do,
> to search a huge DB column with wildcards, the difficulty is
> that the wildcard chould be the 1st character.
> e.g. search for "*ello*funny*"

> The databasse is in CODEBASE(xbase), and there isn't a function to do that.
> So, I've been trying to do it myself.
> I've been looking at some search engines in the WEB and
> i find all the engines require at least 1 character at the start of
> the search criteria!
> I'm pretty sure there must be some theory/practical way of
> doing this .
> can you please direct me to a book or web site etc....

> thank you for yr help,
> cheers
> mike

> --
>     /-----------------------------------------------/ \--\--\  \-- \--
>    /                                               /---\  \  \ \\   \

>  /-----------------------------------------------/There are several amazingly fast text search algorithms. I don't know how

computer literacy you are, but you could look some algorithm books, like
Knuth's, for example.
Of course, this algorithms are useful for searching *one* string in text,
but I think you could easily make it suit your needs. After all, if you
look the string "*xyz*abc*" you are really looking for two strings: "xyz"
and "abc".
I hope this helps. Best Regards,

Luis

 
 
 

Theory&Practical Wildcard searches in DB quest?mlml

Post by Udi Manb » Tue, 23 Jul 1996 04:00:00




Quote:

>   That said, you might consider the tool 'glimpse' available at
>   <ftp://cs.arizona.edu/glimpse/glimpse-3.0.src.tar.Z>. This tool runs
>in
>   batch (usually overnight) and creates an index(outside any existing
>database)
>   which can be used with some pattern matching and in any event runs
>   very fast so that multiple uses aren't bad performance-wise.

>   However you have to compile it youself, etc, unless you're on a Sun.

>    - Nigel.

Glimpse indeed performs fast pattern matching with a small index.
It is now in version 3.6.  Binaries for most UNIX platforms
(along with documentation, demos, and the source) are available at
http://glimpse.cs.arizona.edu/

-- Udi

 
 
 

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