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Posted to issues@lucene.apache.org by "Michael McCandless (Jira)" <ji...@apache.org> on 2021/05/18 17:29:00 UTC
[jira] [Commented] (LUCENE-9963) Flatten graph filter has errors
when there are holes at beginning or end of alternate paths
[ https://issues.apache.org/jira/browse/LUCENE-9963?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17347083#comment-17347083 ]
Michael McCandless commented on LUCENE-9963:
--------------------------------------------
[Disclaimer: I work with [~Geoffrey Lawson] at Amazon's customer-facing product search, now 100% migrated to Apache Lucene]
Whoa, great catch [~Geoffrey Lawson]! What a simple test case too. Holes are especially tricky for graph token filters since they (might) disconnect the graph into two parts. It's scary that NOT under {{assertions}} this token filter might just lose things.
Could you open a PR with just these test cases? Then we can add inlined comments, iterate towards a fix, etc.
Do you have an idea how to fix this?
> 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
>
> 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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