[jira] [Resolved] (LUCENE-9963) Flatten graph filter has errors when there are holes at beginning or end of alternate paths

["Geoffrey Lawson (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/LUCENE-9963?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Geoffrey Lawson resolved LUCENE-9963.
-------------------------------------
    Resolution: Fixed

> Flatten graph filter has errors when there are holes at beginning or end of alternate paths
> -------------------------------------------------------------------------------------------
>
>                 Key: LUCENE-9963
>                 URL: https://issues.apache.org/jira/browse/LUCENE-9963
>             Project: Lucene - Core
>          Issue Type: Bug
>          Components: modules/analysis
>    Affects Versions: 8.8
>            Reporter: Geoffrey Lawson
>            Priority: Major
>          Time Spent: 7.5h
>  Remaining Estimate: 0h
>
> If asserts are enabled having gaps at the beginning or end of an alternate path can result in assertion errors
> ex: 
>  
> {code:java}
> java.lang.AssertionError: 2
> at  org.apache.lucene.analysis.core.FlattenGraphFilter.releaseBufferedToken(FlattenGraphFilter.java:195)
> {code}
>  
> Or
>  
> {code:java}
> java.lang.AssertionError
> at org.apache.lucene.analysis.core.FlattenGraphFilter.releaseBufferedToken(FlattenGraphFilter.java:191)
> {code}
>  
>  
> If asserts are not enabled these the same conditions will result in either IndexOutOfBounds Exceptions, or dropped tokens.
>  
> {code:java}
> java.lang.ArrayIndexOutOfBoundsException: Index -2 out of bounds for length 8
> at org.apache.lucene.util.RollingBuffer.get(RollingBuffer.java:109)
> at org.apache.lucene.analysis.core.FlattenGraphFilter.incrementToken(FlattenGraphFilter.java:325)
> {code}
>  
> These issues can be recreated with the following unit tests
> {code:java}
> public void testAltPathFirstStepHole() throws IOException {
>  TokenStream in = new CannedTokenStream(0, 3, new Token[]{
>  token("abc",1, 3, 0, 3),
>  token("b",1, 1, 1, 2),
>  token("c",1, 1, 2, 3)
>  });
>  TokenStream out = new FlattenGraphFilter(in);
>  assertTokenStreamContents(out,
>  new String[]{"abc", "b", "c"},
>  new int[] {0, 1, 2},
>  new int[] {3, 2, 3}, 
>  new int[] {1, 1, 1},
>  new int[] {3, 1, 1}, //token 0 may need to be len 1 after flattening
>  3);
> }{code}
> {code:java}
> public void testAltPathLastStepHole() throws IOException {
>  TokenStream in = new CannedTokenStream(0, 4, new Token[]{
>  token("abc",1, 3, 0, 3),
>  token("a",0, 1, 0, 1),
>  token("b",1, 1, 1, 2),
>  token("d",2, 1, 3, 4)
>  });
>  TokenStream out = new FlattenGraphFilter(in);
>  assertTokenStreamContents(out,
>  new String[]{"abc", "a", "b", "d"},
>  new int[] {0, 0, 1, 3},
>  new int[] {1, 1, 2, 4},
>  new int[] {1, 0, 1, 2},
>  new int[] {3, 1, 1, 1},
>  4);
> }{code}
> {code:java}
> public void testAltPathLastStepHoleWithoutEndToken() throws IOException {
>  TokenStream in = new CannedTokenStream(0, 2, new Token[]{
>  token("abc",1, 3, 0, 3),
>  token("a",0, 1, 0, 1),
>  token("b",1, 1, 1, 2)
>  });
>  TokenStream out = new FlattenGraphFilter(in);
>  assertTokenStreamContents(out,
>  new String[]{"abc", "a", "b"},
>  new int[] {0, 0, 1},
>  new int[] {1, 1, 2},
>  new int[] {1, 0, 1},
>  new int[] {1, 1, 1},
>  2);
> }{code}
> I believe Lucene-8723 is a related issue as it looks like the last token in an alternate path is being deleted.



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