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From "Gwyn Carwardine" <g...@carwardine.net>
Subject lucene hits vs topdocs
Date Sun, 20 Nov 2011 18:51:03 GMT
Hi

I last used dotLucene 143 and now I'm wanting to upgrade to 294.

What I've discovered is that there are quite a few changes..

One of them is in respect of Search. Previously one supplied a query and
received a number of hits. I didn't have an issue with preservation of state
so was quite happy to page through the stored hits

Now it has changed it also recommends passing the number of results required
(as in top xx results) so I'm considering how to refactor my code.

In the simplest way I guess I could retrieve all results as I did previously
and then paginate through them, or I could use the re-querying approach. But
this suggests for let's say 10 results per page that I query for 10 docs and
then when the user scrolls to the next page I re-query for 20 docs and
ignore the first 10 and so on and so forth.

What initially strikes me about this is that in a fluid environment (where
changes are constantly being re-indexed) it is possible that an item that
would come in an number 11 on the first call (and hence not shown on page 1)
would now move to number 10 on the second call (and hence not shown of page
2).

I would expect as a user that if I do a query and then page through it then
it is the same result set I am paging through and not one that could be
constantly changing (especially if I am paging through a bit slowly).

I am using Lucene as a text search within an information mgt product that
does have lots of updates happening so this could well happen. And it only
needs to happen once and someone miss a key bit of info for it to be
embarrassing.

So I'm curious as to how people out there actually do this. Yes holding
state is a pain but I do that already. 

It just seems that Lucene is pointing towards "tell me how many" and so I
really don't want to go against the tide (or it'll likely be painful next
time I upgrade!)

Thanks in advance




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