[LUCENE-1683] RegexQuery matches terms the input regex doesn't actually match

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.3.2
• Fix Version/s: 2.9
• Component/s: modules/other
• Lucene Fields: New
• Assignee: Michael McCandless
• Reporter: Trejkaz
• Created: 11/Jun/09 01:41
• Updated: 28/Aug/22 12:02
• Resolved: 31/Jul/09 18:03

Description

I was writing some unit tests for our own wrapper around the Lucene regex classes, and got tripped up by something interesting.

The regex "cat." will match "cats" but also anything with "cat" and 1+ following letters (e.g. "cathy", "catcher", ...) It is as if there is an implicit .* always added to the end of the regex.

Here's a unit test for the behaviour I would expect myself:

@Test
public void testNecessity() throws Exception {
File dir = new File(new File(System.getProperty("java.io.tmpdir")), "index");
IndexWriter writer = new IndexWriter(dir, new StandardAnalyzer(), true);
try

{ Document doc = new Document(); doc.add(new Field("field", "cat cats cathy", Field.Store.YES, Field.Index.TOKENIZED)); writer.addDocument(doc); }

finally

{ writer.close(); }

IndexReader reader = IndexReader.open(dir);
try

{ TermEnum terms = new RegexQuery(new Term("field", "cat.")).getEnum(reader); assertEquals("Wrong term", "cats", terms.term()); assertFalse("Should have only been one term", terms.next()); }

finally

{ reader.close(); }

}

This test fails on the term check with terms.term() equal to "cathy".

Our workaround is to mangle the query like this:

String fixed = String.format("(?:%s)$", original);