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https://issues.apache.org/jira/browse/LUCENE-1821?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12745977#action_12745977
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Tim Smith commented on LUCENE-1821:
-----------------------------------
{quote}
It was an implementation detail. If you look at MultiSearcher, Searchable,
Searcher and how the API is put together, you can see we don't support that
type of thing. I think its fairly clear after a little thought.
You can limit your API's to handle just IndexSearchers, but as a project, we
cannot.
{quote}
I totally understand your resistance here. I get that i'm really utilizing
advanced lucene concepts at very low levels (and these are subject to some
changes that i will have to absorb with new versions)
bq. Its okay to pass the Reader because its a contextless Reader. There is no
value in also passing a contextless Searcher
well, when you pass the Searcher that contains Reader, the Reader is no longer
contextless.
also, the context of the Searcher can be fairly well defined (its a "leaf"
Searcher. the one that actually called Weight.scorer())
Also, looking a bit more at MultiSearcher semantics, sorting requires this
"leaf" Searcher context in order to work already
MultiSearcher just takes the top docs from each underlaying Searchable, adjusts
the docids to the MultiSearcher Context, and sends them through another
priority queue
So, this "leaf" Searcher context concept is required by sorting already.
I just want my Scorer to be given this "leaf" context as well
Also, since it is a "leaf" context, the Weight.scorer() method could have the
following interface:
{code}
/**
* @param searcher The IndexSearcher that contains reader.
*/
public Scorer scorer(IndexSearcher searcher, IndexReader reader, boolean
allowDocsInOrder, boolean topScorer);
{code}
then, with the patch i posted, i could call:
searcher.getIndexReaderBase(reader)
and i'm all set
> Weight.scorer() not passed doc offset for "sub reader"
> ------------------------------------------------------
>
> Key: LUCENE-1821
> URL: https://issues.apache.org/jira/browse/LUCENE-1821
> Project: Lucene - Java
> Issue Type: Bug
> Components: Search
> Affects Versions: 2.9
> Reporter: Tim Smith
> Fix For: 2.9
>
> Attachments: LUCENE-1821.patch
>
>
> Now that searching is done on a per segment basis, there is no way for a
> Scorer to know the "actual" doc id for the document's it matches (only the
> relative doc offset into the segment)
> If using caches in your scorer that are based on the "entire" index (all
> segments), there is now no way to index into them properly from inside a
> Scorer because the scorer is not passed the needed offset to calculate the
> "real" docid
> suggest having Weight.scorer() method also take a integer for the doc offset
> Abstract Weight class should have a constructor that takes this offset as
> well as a method to get the offset
> All Weights that have "sub" weights must pass this offset down to created
> "sub" weights
> Details on workaround:
> In order to work around this, you must do the following:
> * Subclass IndexSearcher
> * Add "int getIndexReaderBase(IndexReader)" method to your subclass
> * during Weight creation, the Weight must hold onto a reference to the passed
> in Searcher (casted to your sub class)
> * during Scorer creation, the Scorer must be passed the result of
> YourSearcher.getIndexReaderBase(reader)
> * Scorer can now rebase any collected docids using this offset
> Example implementation of getIndexReaderBase():
> {code}
> // NOTE: more efficient implementation can be done if you cache the result if
> gatherSubReaders in your constructor
> public int getIndexReaderBase(IndexReader reader) {
> if (reader == getReader()) {
> return 0;
> } else {
> List readers = new ArrayList();
> gatherSubReaders(readers);
> Iterator iter = readers.iterator();
> int maxDoc = 0;
> while (iter.hasNext()) {
> IndexReader r = (IndexReader)iter.next();
> if (r == reader) {
> return maxDoc;
> }
> maxDoc += r.maxDoc();
> }
> }
> return -1; // reader not in searcher
> }
> {code}
> Notes:
> * This workaround makes it so you cannot serialize your custom Weight
> implementation
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