Mailing List Archive

> From: Victor Hadianto
>
> A bit of code might help illustrate my situation:
>
> IndexSearcher searcher = new IndexSearcer(dir);
>
> Hits hits = search.search(query);
>
> for (int i = 0; i < hits.length(); i++) {
>
> .... get the document and do modification here
>
> IndexReader reader = new IndexReader(dir);
> reader.delete(new Term("id", doc.get("id");
> reader.close();
>
> IndexWriter writer = new IndexWriter( ... );
> writer.add(doc);
> writer.close();
> }
>
> searcher.close();
>
> Is this OK?

Looks fine to me.

The restrictions are that you can only have one of the following open at a
time:
- a reader that you've done deletions on; or
- a writer
The theme is that only one thing can modify an index at once, but many can
read it. So you can have as many readers open as you like that are not
doing deletions while either a writer is open *or* another reader is open
that is doing deletions.

You could do this much more efficiently by iterating through the hits twice,
once to do all the deletions on a single reader, then close that reader, and
iterate through the hits again adding each to a single writer, something
like:

IndexReader deleter = new IndexReader(dir);
Hits hits = search.search(query);
for (int i = 0; i < hits.length(); i++) {

... get the document ..

deleter.delete(new Term("id", doc.get("id");
}
deleter.close();

IndexWriter writer = new IndexWriter( ... );
Hits hits = search.search(query);
for (int i = 0; i < hits.length(); i++) {

... get the document again, modify it ..
writer.add(doc);
}
writer.close();

searcher.close();

Note that since the searcher is not re-opened, you are guaranteed to get the
same results from the query.

Or, instead of doing the search again, you could save all the documents in
an array, and then add them in a second pass. The point is that performing
a bunch of deletions on a single reader object is *much* faster than opening
and closing a new reader for each deletion, and performing a bunch of
additions on a single writer object is *much* faster than opening and
closing a new writer for each addition.

Doug

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