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https://issues.apache.org/jira/browse/LUCENE-8662?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16754688#comment-16754688
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Adrien Grand commented on LUCENE-8662:
--------------------------------------
Thanks for the ping [[email protected]].
[~yuanyun.cn] I'd rather override {{seekExact}} in {{ExitableTermsEnum}} to
delegate to the wrapped instance. In general we only delegate abstract methods
in Filter* classes so that there is a minimal set of methods that need to be
extended in order to write a well-behaved terms enum wrapper. For instance if
FilterTermsEnum delegated seekExact, then any sub class that modifies the
content of the terms enum (eg. filtering some terms out) would have to override
both seekCeil and seekExact while today overriding seekCeil is enough. If we
think that it is a performance trap, we could discuss making
{{TermsEnum#seekExact}} abstract and delegate it in {{FilterTermsEnum}} but
this wouldn't be a small change so we might want a stronger case for it.
> Override seekExact(BytesRef) in FilterLeafReader.FilterTermsEnum
> ----------------------------------------------------------------
>
> Key: LUCENE-8662
> URL: https://issues.apache.org/jira/browse/LUCENE-8662
> Project: Lucene - Core
> Issue Type: Improvement
> Components: core/search
> Affects Versions: 5.5.5, 6.6.5, 7.6, 8.0
> Reporter: jefferyyuan
> Priority: Major
> Labels: query
> Fix For: 8.0, 7.7
>
> Attachments: output of test program.txt
>
> Time Spent: 10m
> Remaining Estimate: 0h
>
> Recently in our production, we found that Sole uses a lot of memory(more than
> 10g) during recovery or commit for a small index (3.5gb)
> The stack trace is:
>
> {code:java}
> Thread 0x4d4b115c0
> at org.apache.lucene.store.DataInput.readVInt()I (DataInput.java:125)
> at org.apache.lucene.codecs.blocktree.SegmentTermsEnumFrame.loadBlock()V
> (SegmentTermsEnumFrame.java:157)
> at
> org.apache.lucene.codecs.blocktree.SegmentTermsEnumFrame.scanToTermNonLeaf(Lorg/apache/lucene/util/BytesRef;Z)Lorg/apache/lucene/index/TermsEnum$SeekStatus;
> (SegmentTermsEnumFrame.java:786)
> at
> org.apache.lucene.codecs.blocktree.SegmentTermsEnumFrame.scanToTerm(Lorg/apache/lucene/util/BytesRef;Z)Lorg/apache/lucene/index/TermsEnum$SeekStatus;
> (SegmentTermsEnumFrame.java:538)
> at
> org.apache.lucene.codecs.blocktree.SegmentTermsEnum.seekCeil(Lorg/apache/lucene/util/BytesRef;)Lorg/apache/lucene/index/TermsEnum$SeekStatus;
> (SegmentTermsEnum.java:757)
> at
> org.apache.lucene.index.FilterLeafReader$FilterTermsEnum.seekCeil(Lorg/apache/lucene/util/BytesRef;)Lorg/apache/lucene/index/TermsEnum$SeekStatus;
> (FilterLeafReader.java:185)
> at
> org.apache.lucene.index.TermsEnum.seekExact(Lorg/apache/lucene/util/BytesRef;)Z
> (TermsEnum.java:74)
> at
> org.apache.solr.search.SolrIndexSearcher.lookupId(Lorg/apache/lucene/util/BytesRef;)J
> (SolrIndexSearcher.java:823)
> at
> org.apache.solr.update.VersionInfo.getVersionFromIndex(Lorg/apache/lucene/util/BytesRef;)Ljava/lang/Long;
> (VersionInfo.java:204)
> at
> org.apache.solr.update.UpdateLog.lookupVersion(Lorg/apache/lucene/util/BytesRef;)Ljava/lang/Long;
> (UpdateLog.java:786)
> at
> org.apache.solr.update.VersionInfo.lookupVersion(Lorg/apache/lucene/util/BytesRef;)Ljava/lang/Long;
> (VersionInfo.java:194)
> at
> org.apache.solr.update.processor.DistributedUpdateProcessor.versionAdd(Lorg/apache/solr/update/AddUpdateCommand;)Z
> (DistributedUpdateProcessor.java:1051)
> {code}
> We reproduced the problem locally with the following code using Lucene code.
> {code:java}
> public static void main(String[] args) throws IOException {
> FSDirectory index = FSDirectory.open(Paths.get("the-index"));
> try (IndexReader reader = new
> ExitableDirectoryReader(DirectoryReader.open(index),
> new QueryTimeoutImpl(1000 * 60 * 5))) {
> String id = "the-id";
> BytesRef text = new BytesRef(id);
> for (LeafReaderContext lf : reader.leaves()) {
> TermsEnum te = lf.reader().terms("id").iterator();
> System.out.println(te.seekExact(text));
> }
> }
> }
> {code}
>
> I added System.out.println("ord: " + ord); in
> codecs.blocktree.SegmentTermsEnum.getFrame(int).
> Please check the attached output of test program.txt.
>
> We found out the root cause:
> we didn't implement seekExact(BytesRef) method in
> FilterLeafReader.FilterTerms, so it uses the base class
> TermsEnum.seekExact(BytesRef) implementation which is very inefficient in
> this case.
> {code:java}
> public boolean seekExact(BytesRef text) throws IOException {
> return seekCeil(text) == SeekStatus.FOUND;
> }
> {code}
> The fix is simple, just override seekExact(BytesRef) method in
> FilterLeafReader.FilterTerms
> {code:java}
> @Override
> public boolean seekExact(BytesRef text) throws IOException {
> return in.seekExact(text);
> }
> {code}
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