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Posted to dev@lucene.apache.org by Ben Pryor <BP...@widen.com> on 2004/06/24 17:29:26 UTC

Suffix query

Hi,
 I have read up on the negative aspects of a SuffixQuery class. Be these as
they may, a situation came up where one is required for an application I'm
working on, so I started with the PrefixQuery class and modified it to match
suffixes instead. The relevant method that changed was the rewrite() method:

public Query rewrite(IndexReader reader) throws IOException 
{
	BooleanQuery query = new BooleanQuery();
	Term startTerm = new Term(suffix.field(), "");
	TermEnum enumerator = reader.terms(startTerm);
	try 
	{
  		String suffixText = suffix.text();
  		String suffixField = suffix.field();
  		do 
  		{
			Term term = enumerator.term();
			if (term != null && term.field() != suffixField)
			{
				break;
			}
							
			if (term != null &&
term.text().endsWith(suffixText)) 
			{
	  			TermQuery tq = new TermQuery(term);	  //
found a match
	  			tq.setBoost(getBoost());              // set
the boost
	  			query.add(tq, false, false);		  //
add to query
			} 
  		} 
  		while (enumerator.next());
	} 
	finally 
	{
  		enumerator.close();
	}
	return query;
}

Questions: How na�ve is this implementation? How bad will performance be on
a large index, and is there a more efficient way to do this?

Thanks for advice,
Ben

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Re: Suffix query

Posted by Erik Hatcher <er...@ehatchersolutions.com>.
WildcardQuery supports suffix (*something) queries when used through 
the API (QueryParser does not allow asterisks at the beginning).  So I 
don't think what you've done is necessary... just use a WildcardQuery 
with a leading asterisk.

There are alternative approaches to this by changing how you index to 
accommodate suffix queries (reverse what goes in, reverse it and do a 
prefix query during querying).

	Erik


On Jun 24, 2004, at 11:29 AM, Ben Pryor wrote:

> Hi,
>  I have read up on the negative aspects of a SuffixQuery class. Be 
> these as
> they may, a situation came up where one is required for an application 
> I'm
> working on, so I started with the PrefixQuery class and modified it to 
> match
> suffixes instead. The relevant method that changed was the rewrite() 
> method:
>
> public Query rewrite(IndexReader reader) throws IOException
> {
> 	BooleanQuery query = new BooleanQuery();
> 	Term startTerm = new Term(suffix.field(), "");
> 	TermEnum enumerator = reader.terms(startTerm);
> 	try
> 	{
>   		String suffixText = suffix.text();
>   		String suffixField = suffix.field();
>   		do
>   		{
> 			Term term = enumerator.term();
> 			if (term != null && term.field() != suffixField)
> 			{
> 				break;
> 			}
> 							
> 			if (term != null &&
> term.text().endsWith(suffixText))
> 			{
> 	  			TermQuery tq = new TermQuery(term);	  //
> found a match
> 	  			tq.setBoost(getBoost());              // set
> the boost
> 	  			query.add(tq, false, false);		  //
> add to query
> 			}
>   		}
>   		while (enumerator.next());
> 	}
> 	finally
> 	{
>   		enumerator.close();
> 	}
> 	return query;
> }
>
> Questions: How naïve is this implementation? How bad will performance 
> be on
> a large index, and is there a more efficient way to do this?
>
> Thanks for advice,
> Ben
>
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> To unsubscribe, e-mail: lucene-dev-unsubscribe@jakarta.apache.org
> For additional commands, e-mail: lucene-dev-help@jakarta.apache.org


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