On 9/20/06, Clare <[EMAIL PROTECTED]> wrote:
> Hi i'm using ferret to enable geographical postcode. I take a postcode
> and distance in miles from the user, strip off the outcode and then
> retrieve the associated x y coordinates in metres from the db. Then i
> get two temp x's and y's and search for all results that are within the
> box, see code below.
>
> Problems start to occur when i search on big distances so for example
>
> 40 miles from "G1"
> VoObject.ferret_index.search(" x:[206826 335573] AND y:[590526
> 719273]").total_hits
> => 165
>
>
> 300 miles
> VoObject.ferret_index.search("y:[172098 1137702]").total_hits
> Ferret::QueryParser::QueryParseException: Error occured in q_range.c:121
> - range_new
> Upper bound must be greater than lower bound. "1137702" <
> "172098"
>
> from
> /usr/lib/ruby/gems/1.8/gems/ferret-0.10.1/lib/ferret/index.rb:572:in
> `parse'
> from
> /usr/lib/ruby/gems/1.8/gems/ferret-0.10.1/lib/ferret/index.rb:572:in
> `process_query'
> from
> /usr/lib/ruby/gems/1.8/gems/ferret-0.10.1/lib/ferret/index.rb:560:in
> `do_search'
> from
> /usr/lib/ruby/gems/1.8/gems/ferret-0.10.1/lib/ferret/index.rb:233:in
> `search'
> from /usr/lib/ruby/1.8/monitor.rb:229:in `synchronize'
> from
> /usr/lib/ruby/gems/1.8/gems/ferret-0.10.1/lib/ferret/index.rb:232:in
> `search'
> from (irb):16
>
>
> So what am i doing wrong? How have other people used ferret for
> geographical searches? Is there another way that i can define the range
> so that it works properly?
>
> because I'm also getting other crazy and just plain wrong results
>
> VoObject.ferret_index.search("y:[0 9]").total_hits
> => 167
>
> thats telling me that all the test data is with 8 metres of the
> origin...
>
> thanks in advance.
> clare
>
>
> if their_outcode && their_outcode.size > 0
> temp_hwz = HwzPostcode.find(:first, :conditions => ['outcode =
> ?',their_outcode])
> range_x_left = temp_hwz.x - (postcode_distance.to_f*1.60934 *
> 1000)
> range_x_right = temp_hwz.x + (postcode_distance.to_f*1.60934 *
> 1000)
> range_y_top = temp_hwz.y + (postcode_distance.to_f*1.60934 *
> 1000)
> range_y_bottom = temp_hwz.y - (postcode_distance.to_f*1.60934 *
> 1000)
>
> query += " AND x:[#{range_x_left.to_i} #{range_x_right.to_i}] AND
> y:[#{range_y_bottom.to_i} #{range_y_top.to_i}]"
> end
Hi Clare,
Ranges are calculated according to lexical ordering, not numerical
ordering. Try this:
puts ["0", "9", "167"].sort
You'll see that "167" does indeed fall between "0" and "9". Now try this:
puts ["000", "009", "167"].sort
So that should explain what you have to do. You need to pad all
numbers to a fixed width. Alternatively you could build a custom
IntegerRangeFilter and combine it with a ConstantScoreQuery. Here is
an example for Floats:
require 'rubygems'
require 'ferret'
class FloatRangeFilter
attr_accessor :field, :upper, :lower, :upper_op, :lower_op
def initialize(field, options)
@field = field
@upper = options[:<] || options[:<=]
@lower = options[:>] || options[:>=]
if @upper.nil? and @lower.nil?
raise ArgError, "Must specify a bound"
end
@upper_op = options[:<].nil? ? :<= : :<
@lower_op = options[:>].nil? ? :>= : :>
end
def bits(index_reader)
bit_vector = Ferret::Utils::BitVector.new
term_doc_enum = index_reader.term_docs
index_reader.terms(@field).each do |term, freq|
float = term.to_f
next if @upper and not float.send(@upper_op, @upper)
next if @lower and not float.send(@lower_op, @lower)
term_doc_enum.seek(@field, term)
term_doc_enum.each {|doc_id, freq| bit_vector.set(doc_id)}
end
return bit_vector
end
def hash
return @field.hash ^ @upper.hash ^ @lower.hash ^
@upper_op.hash ^ @lower_op.hash
end
def eql?(o)
return (o.instance_of?(FloatRangeFilter) and @field == o.field and
@upper == o.upper and @lower == o.lower and
@upper_op == o.upper_op and @lower_op == o.lower_op)
end
end
You'll have to work out what is going on here yourself though. I have
no time for explanation. Note that this won't perform very well
compared to the padded field version because so much is going on in
the Ruby code. I could possibly be persuaded to implement this in C.
Cheers,
Dave
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