[jira] [Commented] (LUCENE-6661) Allow queries to opt out of caching

["Adrien Grand (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/LUCENE-6661?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14615703#comment-14615703 ] 

Adrien Grand commented on LUCENE-6661:
--------------------------------------

One issue I have with marker interfaces is that they do not support wrapping. Eg. if you put such a query in a BooleanQuery, then the BooleanQuery would be considered cacheable although it should not be cached either.

One way to work around this issue would be to make a query that is not equal to any other query but itself? Eg:

{code}
class MyQuery extends Query {

  private Object identity = null;

  boolean equals(Object o) {
    if (super.equals(o) == false) {
      return false;
    }
    MyQuery that = (MyQuery) o;
    return identity == that.identity;
  }

  int hashcode() {
    return 31 * super.hashcode() + Objects.hashcode(identity);
  }

  Weight createWeight(IndexSearcher searcher, boolean needsScores) {
    // create a query that will be equal to no other query
    // given that we use Weight.getQuery() for caching
    Query weightQuery = clone();
    weightQuery.identity = new Object();
    return new Weight(weightQuery) {
      // weight impl
    };
  }

}
{code}

Given that the cache only caches queries that are reused, it will never be cached.

> Allow queries to opt out of caching
> -----------------------------------
>
>                 Key: LUCENE-6661
>                 URL: https://issues.apache.org/jira/browse/LUCENE-6661
>             Project: Lucene - Core
>          Issue Type: Improvement
>    Affects Versions: 5.2
>            Reporter: Terry Smith
>            Priority: Minor
>         Attachments: LUCENE-6661.patch
>
>
> Some queries have out-of-band dependencies that make them incompatible with caching, it'd be great if they could opt out of the new fancy query/filter cache in IndexSearcher.
> This affects DrillSidewaysQuery and any user-provided custom Query implementations.



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