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LUCENE-6664: be more robust to broken token stream offsets

This commit is contained in:
Mike McCandless 2017-01-03 06:47:47 -05:00
parent b4a002f7d8
commit f6fb6941bb
1 changed files with 12 additions and 19 deletions
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29
lucene/analysis/common/src/java/org/apache/lucene/analysis/synonym/FlattenGraphFilter.java
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@ -17,22 +17,6 @@
package org.apache.lucene.analysis.synonym;
/**
* This filter "casts" token graphs down into a "flat" form,
* for indexing. This is an inherently lossy process: nodes (positions)
* along side paths are forcefully merged.
*
* <p>In general this means the output graph will accept token sequences
* that the input graph did not accept, and will also fail to accept
* token sequences that the input graph did accept.
*
* <p>This is only necessary at indexing time because Lucene cannot yet index
* an arbitrary token graph. At search time there are better options, e.g.
* the experimental <code>TermAutomatonQuery</code> in sandbox.
*
* @lucene.experimental
*/
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
@ -49,7 +33,12 @@ import org.apache.lucene.util.RollingBuffer;
* Converts an incoming graph token stream, such as one from
* {@link SynonymGraphFilter}, into a flat form so that
* all nodes form a single linear chain with no side paths. Every
* path through the graph touches every node.
* path through the graph touches every node. This is necessary
* when indexing a graph token stream, because the index does not
* save {@link PositionLengthAttribute} and so it cannot
* preserve the graph structure. However, at search time,
* query parsers can correctly handle the graph and this token
* filter should <b>not</b> be used.
*
* <p>If the graph was not already flat to start, this
* is likely a lossy process, i.e. it will often cause the
@ -234,7 +223,11 @@ public final class FlattenGraphFilter extends TokenFilter {
// which would otherwise happen if the replacement has more tokens
// than the input:
int startOffset = Math.max(lastStartOffset, output.startOffset);
offsetAtt.setOffset(startOffset, outputEndNode.endOffset);
// We must do this in case the incoming tokens have broken offsets:
int endOffset = Math.max(startOffset, outputEndNode.endOffset);
offsetAtt.setOffset(startOffset, endOffset);
lastStartOffset = startOffset;
if (inputNode.nextOut == inputNode.tokens.size()) {