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https://issues.apache.org/jira/browse/LUCENE-7260?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15261667#comment-15261667
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Dawid Weiss commented on LUCENE-7260:
-------------------------------------
Do something with the result of the parsing, otherwise the result may be junk
due to jvm optimizing out what it thinks is dead code. If this is indeed still
the case it should be fairly easy to find by bisecting codebase between the two
releases.
> StandardQueryParser is over 100 times slower in v5 compared to v3
> -----------------------------------------------------------------
>
> Key: LUCENE-7260
> URL: https://issues.apache.org/jira/browse/LUCENE-7260
> Project: Lucene - Core
> Issue Type: Improvement
> Components: modules/queryparser
> Affects Versions: 5.4.1
> Environment: Java 8u51
> Reporter: Trejkaz
> Labels: performance
>
> The following test code times parsing a large query.
> {code}
> import org.apache.lucene.analysis.KeywordAnalyzer;
> //import org.apache.lucene.analysis.core.KeywordAnalyzer;
> import org.apache.lucene.queryParser.standard.StandardQueryParser;
> //import org.apache.lucene.queryparser.flexible.standard.StandardQueryParser;
> import org.apache.lucene.search.BooleanQuery;
> public class LargeQueryTest {
> public static void main(String[] args) throws Exception {
> BooleanQuery.setMaxClauseCount(50_000);
> StringBuilder builder = new StringBuilder(50_000*10);
> builder.append("id:( ");
> boolean first = true;
> for (int i = 0; i < 50_000; i++) {
> if (first) {
> first = false;
> } else {
> builder.append(" OR ");
> }
> builder.append(String.valueOf(i));
> }
> builder.append(" )");
> String queryString = builder.toString();
> StandardQueryParser parser2 = new StandardQueryParser(new
> KeywordAnalyzer());
> for (int i = 0; i < 10; i++) {
> long t0 = System.currentTimeMillis();
> parser2.parse(queryString, "nope");
> long t1 = System.currentTimeMillis();
> System.out.println(t1-t0);
> }
> }
> }
> {code}
> For Lucene 3.6.2, the timings settle down to 200~300 with the fastest being
> 207.
> For Lucene 5.4.1, the timings settle down to 20000~30000 with the fastest
> being 22444.
> So at some point, some change made the query parser 100 times slower. I would
> suspect that it has something to do with how the list of children is now
> handled. Every time someone gets the children, it copies the list. Every time
> someone sets the children, it walks through to detach parent references and
> then reattaches them all again.
> If it were me, I would probably make these collections immutable so that I
> didn't have to defensively copy them.
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