Reverse sorting

Ruby Apps Ferret
1

I am getting strange results when I reverse sort a query. I am sorting
by date, but it doesn’t seem to be related to dates (I have tried just
integers). I also paginate the results. Items in the result set are
sometimes duplicated and the not ordered at all. When I try a
non-reverse sort I don’t see duplicates and the ordering is correct. Any
ideas what is going on? Thanks

2

On 7/13/06, Floyd M. [email protected] wrote:

I am getting strange results when I reverse sort a query. I am sorting
by date, but it doesn’t seem to be related to dates (I have tried just
integers). I also paginate the results. Items in the result set are
sometimes duplicated and the not ordered at all. When I try a
non-reverse sort I don’t see duplicates and the ordering is correct. Any
ideas what is going on? Thanks

No idea. Could you show us some example code. Preferably with a short
test case.

Cheers,
Dave

3

Here is the index snippet:

doc = Ferret::Document::Document.new

insert the id

doc << Ferret::Document::Field.new( “id”, post.id,
Ferret::Document::Field::Store::YES,
Ferret::Document::Field::Index::UNTOKENIZED )

insert the date

doc << Ferret::Document::Field.new( “created_at”, post.created_at,
Ferret::Document::Field::Store::NO,
Ferret::Document::Field::Index::UNTOKENIZED )

add some other stuff …

write to the index

index << doc

Here is the query snippet:

sort_fields = []
sort_fields << Ferret::Search::SortField.new
( “created_at”, :sort_type =>
Ferret::Search::SortField::SortType::INTEGER, :reverse => true )

search the index

top_docs = index.search( query, { :first_doc =>
first_doc , :num_docs => 5, :sort => sort_fields } )

4

On 7/13/06, Floyd M. [email protected] wrote:

Ferret::Document::Field::Index::UNTOKENIZED )

search the index

top_docs = index.search( query, { :first_doc =>
first_doc , :num_docs => 5, :sort => sort_fields } )

I’m not exactly sure what post.created_at but if it’s a Time object
then you need to convert it to a string that will sort correctly as a
string. ie use strftime(“%Y%m%d”) (use whatever precision you need.
Here is an example which adds 100 documents with 100 random dates in
the last 100 days;

require ‘rubygems’
require ‘ferret’
include Ferret::Index
include Ferret::Search

index = Index.new
t = Time.now

100.times do
index << {:id => “x”,
:date => (t-246060*rand(100)).strftime(“%Y%m%d”)}
end

sort_fields = [SortField.new(:date,
:sort_type => SortField::SortType::INTEGER,
:reverse => true)]

10.times do |start|
index.search_each(“x”,
:first_doc => start*10,
:num_docs => 10,
:sort => sort_fields) do |doc_id, score|
puts index[doc_id][:date]
end
end

5

On 7/13/06, Floyd M. [email protected] wrote:

The field is a DateTime.

So I tried what you suggested and no luck. I noticed that when I
remove the first_doc and num_doc options it appears to work correctly
(getting all of the docs in the right order).

I’m sorry, I can’t really help unless I can see an example that isn’t
working. Try modifying the code that I posted previously to match more
closely what you are doing. Then send back the broken example snippet
and I’ll be able to tell you what is wrong with it or fix the bug if
it exists. As long as the strings going into the index are the same
(ie, in the format “%Y%m%d”) then I can’t see how your results could
be any different.

Cheers,
Dave

6

The field is a DateTime.

So I tried what you suggested and no luck. I noticed that when I
remove the first_doc and num_doc options it appears to work correctly
(getting all of the docs in the right order).