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Posted to java-user@lucene.apache.org by Gwyn Carwardine <gw...@carwardine.net> on 2006/01/23 16:38:49 UTC
Range queries
Two queries about ranges:
1. field:[a TO z] does not return the same as field:[z TO a]
I think it should. The standard QueryParser or even the range query should
ascertain the lowest and highest and switch them around if necessary
2. How do I search for negative numbers in a range. For example field:[-3 TO
2] ?
I don't mind hacking code such that my numbers are indexed as +00000001 and
-00000001 and then I can override the query parser to change my query to
[-0000003 TO +0000002]. However.. "+" is less then "-" in Ascii terms so a
range search isn't going to work terrifically well.. Is there a standard
approach??
-Gwyn
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RE: Range queries
Posted by Gwyn Carwardine <gw...@carwardine.net>.
>> 2. How do I search for negative numbers in a range. For example
>> field:[-3 TO
>> 2] ?
>>
>> I don't mind hacking code such that my numbers are indexed as
>> +00000001 and
>> -00000001 and then I can override the query parser to change my
>> query to
>> [-0000003 TO +0000002]. However.. "+" is less then "-" in Ascii
>> terms so a
>> range search isn't going to work terrifically well.. Is there a
>> standard
>> approach??
>
>You could leave the "+" off for positive numbers. That'd do the
>trick, right? "-" < "0" lexicographically.
>
> Erik
Hi Erik,
good point! Of course it still doesn't work because "-3" is greater then
"-2" !
I've done something else where 0 is represented by 10000000000000000000
Any positive number has a "1" followed by the number left padded with zeroes
to length 19
12345 is therefore 10000000000000012345
Any negative number has a "0" followed by (number - long.minvalue) left
padded with zeroes to length 19
-12345 is therefore 09223372036854763463
This will work fine. Of course it got much more difficult with floating
numbers where you have to mess around with a positive and negative mantissa
and exponent. But it was doable.
-g
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Re: Range queries
Posted by Chris Hostetter <ho...@fucit.org>.
: As Gwyn pointed out, that would make -3 > -2. Personally, I'd use
: unsigned numbers and shift the range -- for 16 bit numbers I'd map
: -32768..32767 to 0..65535 by adding 32768. I guess you could do that by
: having overriding getRangeQuery() (LIA, p207 -- wonderful book).
there are a lot of different techniques for encoding numeric values as
lexigraphically ordered strings, finding the right soluation for any
given case depends mainly on what hte scope of your values is -- if
you're only ever dealing with the numbers 1-10, there are some really
easy options. If you want something that can handle any "long" take a
look at the NumberTools class in SVN. Even if what you want is something
that can handle any int, the technique used in that class can be still be
applied.
As for the query parsing aspect -- subclassing and overriding the
getRangeQuery method to know which fields to encode using your method of
choice is the very easy to do.
-Hoss
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Re: Range queries
Posted by John Haxby <jc...@scalix.com>.
Erik Hatcher wrote:
>> 2. How do I search for negative numbers in a range. For example
>> field:[-3 TO
>> 2] ?
>>
>> I don't mind hacking code such that my numbers are indexed as
>> +00000001 and
>> -00000001 and then I can override the query parser to change my
>> query to
>> [-0000003 TO +0000002]. However.. "+" is less then "-" in Ascii
>> terms so a
>> range search isn't going to work terrifically well.. Is there a
>> standard
>> approach??
>
>
> You could leave the "+" off for positive numbers. That'd do the
> trick, right? "-" < "0" lexicographically.
As Gwyn pointed out, that would make -3 > -2. Personally, I'd use
unsigned numbers and shift the range -- for 16 bit numbers I'd map
-32768..32767 to 0..65535 by adding 32768. I guess you could do that by
having overriding getRangeQuery() (LIA, p207 -- wonderful book).
jch
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Re: Range queries
Posted by Erik Hatcher <er...@ehatchersolutions.com>.
On Jan 23, 2006, at 10:38 AM, Gwyn Carwardine wrote:
> Two queries about ranges:
>
> 1. field:[a TO z] does not return the same as field:[z TO a]
>
> I think it should. The standard QueryParser or even the range query
> should
> ascertain the lowest and highest and switch them around if necessary
This is quite debatable. I personally don't think the ends of the
ranges should be swapped when the left one is greater than the right
one. The word "TO" indicates the user is supplying the ends already
in order.
But if the consensus was to adjust it, I wouldn't object.
> 2. How do I search for negative numbers in a range. For example
> field:[-3 TO
> 2] ?
>
> I don't mind hacking code such that my numbers are indexed as
> +00000001 and
> -00000001 and then I can override the query parser to change my
> query to
> [-0000003 TO +0000002]. However.. "+" is less then "-" in Ascii
> terms so a
> range search isn't going to work terrifically well.. Is there a
> standard
> approach??
You could leave the "+" off for positive numbers. That'd do the
trick, right? "-" < "0" lexicographically.
Erik
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