* @throws IOException if there's a problem with the ShingleFilter reading data or the collector collecting output.
*/
@Override
protected void map(Text key, StringTuple value, final Context context) throws IOException, InterruptedException {
ShingleFilter sf = new ShingleFilter(new IteratorTokenStream(value.getEntries().iterator()), maxShingleSize);
try {
int count = 0; // ngram count
OpenObjectIntHashMap<String> ngrams =
new OpenObjectIntHashMap<String>(value.getEntries().size() * (maxShingleSize - 1));
OpenObjectIntHashMap<String> unigrams = new OpenObjectIntHashMap<String>(value.getEntries().size());
do {
String term = sf.getAttribute(CharTermAttribute.class).toString();
String type = sf.getAttribute(TypeAttribute.class).type();
if ("shingle".equals(type)) {
count++;
ngrams.adjustOrPutValue(term, 1, 1);
} else if (emitUnigrams && !term.isEmpty()) { // unigram
unigrams.adjustOrPutValue(term, 1, 1);
}
} while (sf.incrementToken());
final GramKey gramKey = new GramKey();
ngrams.forEachPair(new ObjectIntProcedure<String>() {
@Override
public boolean apply(String term, int frequency) {
// obtain components, the leading (n-1)gram and the trailing unigram.
int i = term.lastIndexOf(' '); // TODO: fix for non-whitespace delimited languages.
if (i != -1) { // bigram, trigram etc
try {
Gram ngram = new Gram(term, frequency, Gram.Type.NGRAM);
Gram head = new Gram(term.substring(0, i), frequency, Gram.Type.HEAD);
Gram tail = new Gram(term.substring(i + 1), frequency, Gram.Type.TAIL);
gramKey.set(head, EMPTY);
context.write(gramKey, head);
gramKey.set(head, ngram.getBytes());
context.write(gramKey, ngram);
gramKey.set(tail, EMPTY);
context.write(gramKey, tail);
gramKey.set(tail, ngram.getBytes());
context.write(gramKey, ngram);
} catch (IOException e) {
throw new IllegalStateException(e);
} catch (InterruptedException e) {
throw new IllegalStateException(e);
}
}
return true;
}
});
unigrams.forEachPair(new ObjectIntProcedure<String>() {
@Override
public boolean apply(String term, int frequency) {
try {
Gram unigram = new Gram(term, frequency, Gram.Type.UNIGRAM);
gramKey.set(unigram, EMPTY);
context.write(gramKey, unigram);
} catch (IOException e) {
throw new IllegalStateException(e);
} catch (InterruptedException e) {
throw new IllegalStateException(e);
}
return true;
}
});
context.getCounter(Count.NGRAM_TOTAL).increment(count);
sf.end();
} finally {
Closeables.closeQuietly(sf);
}
}