Thank you for these precisions. As I had to do something fast, I coded
the thing as illustrated by the following pseudocode:
IndexReader index;
TermPositions iterator = this.index.termPositions(t); // for each doc
where this term appears
while (iterator.next()) {
int docNr = iterator.doc();
int freq = iterator.freq();
int[] apparitionPositions = new int[freq]; // these are the
positions in the crt doc of the crt term
for (int i = 0; i < freq; i++) {
apparitionPositions[i] = iterator.nextPosition();
}
...
TermPositionVector tpv = (TermPositionVector)
this.index.getTermFreqVector(docNr, "text");
...
// for all possible terms, see if it is close to one of the
elements in apparitionPositions
for (int i = 0; i < terms.length; i++) {
int[] pos = tpv.getTermPositions(i);
... // for each element in pos, check close distance to
the crt term
}
}
My understanding is that this is a less object-oriented way of doing the
same thing as your proposition but please correct me if I'm wrong.
I finally managed to retrieve what I wanted with this code. The problem
is that it is not really parallelizable. If several threads call
getTermFreqVector at the same time, they have to wait after each other.
My multithreaded scenario involved a unique IndexReader on which all
threads ask for term vectors. I wonder if it is possible to avoid this
problem (perhaps by having a pool of IndexReaders, is this a good
practice, wouldn't there be memory problems?). I welcome any ideas on
this subject.
Thank you,
Adrian.
Grant Ingersoll wrote:
There isn't a very clean way to do this just yet, but it is doable.
Index with positions (you might find offsets useful too) and then use
the TermVectorMapper and TermVector API call on the IndexReader (not
the termPositions). Then, you will need to implement a
TermVectorMapper that takes in your position and then reads in the
term vector and gets just those positions around the interested
position. Once you are outside of your window, you can then short
circuit out of the TermVM (I think).
HTH,
Grant
On May 3, 2009, at 2:39 PM, Adrian Dimulescu wrote:
Hello,
I am post-processing a positional index -- with a field like the
following:
doc.add(new Field(Constants.FIELD_TEXT, txt, Store.NO,
Index.ANALYZED, TermVector.WITH_POSITIONS));
At post-processing, I want to retrieve the neighbours of a given term
within a given range. That is, if document x contains the sequence :
"Alabama experienced significant /recovery as the economy of the
state/ transitioned from agriculture to diversified interests in
heavy manufacturing"
for range = 3 and term = "economy", I want to retrieve "recovery as
the *economy* of the state".
I see there is an API call :
IndexReader.termPositions(term)
which retrieves the actual positions of the given term. Is there a
quick way to retrieve its neighbours too, instead of browsing all
terms for all document and see if their position is close to the
position of the central term ?
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