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From "Hoss Man (JIRA)" <>
Subject [jira] [Commented] (SOLR-2716) QueryResultKey hashCode() and equals() is dependent on filter order
Date Fri, 26 Aug 2011 04:26:30 GMT


Hoss Man commented on SOLR-2716:

bq. I wonder if the increased cost in equals() would be worth it... the complete solr request
(including filters) are normally generated by another system, not a user, so one will normally
see filters in the same order anyway.

yeah ... that was the concern i had when this came up on the list.  initially i was thinking
of it as a "sort" cost, but the same general perf concern still applies: if Set.equals is
generally slower then List.equals, then it's better to tell the client "to maximum cache hit
rates, send your filters in a deterministic order"

if perf tests say that the Set equality is just as fast as List equality - go with the set

> QueryResultKey hashCode() and equals() is dependent on filter order
> -------------------------------------------------------------------
>                 Key: SOLR-2716
>                 URL:
>             Project: Solr
>          Issue Type: Improvement
>          Components: search
>    Affects Versions: 3.3
>            Reporter: Neil Prosser
>            Priority: Minor
>         Attachments: SOLR-2716.patch
> The hashCode() and equals() methods of a QueryResultKey are dependent on the order of
the filters meaning that potentially identical result sets are missed when cached.
> Query query = new TermQuery(new Term("field1", "value1"));
> Query filter1 = new TermQuery(new Term("field2", "value2"));
> Query filter2 = new TermQuery(new Term("field3", "value3"));
> List<Query> filters1 = new ArrayList<Query>();
> filters1.add(filter1);
> filters1.add(filter2);
> List<Query> filters2 = new ArrayList<Query>();
> filters2.add(filter2);
> filters2.add(filter1);
> QueryResultKey key1 = new QueryResultKey(query, filters1, null, 0);
> QueryResultKey key2 = new QueryResultKey(query, filters2, null, 0);
> // Both the following assertions fail
> assert key1.equals(key2);
> assert key1.hashCode() == key2.hashCode();

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