[jira] [Created] (SOLR-12635) HashQParserPlugin should be run as a post filter when executed from a ParallelStream

["Varun Thacker (JIRA)" <ji...@apache.org>]

Varun Thacker created SOLR-12635:
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             Summary: HashQParserPlugin should be run as a post filter when executed from a ParallelStream
                 Key: SOLR-12635
                 URL: https://issues.apache.org/jira/browse/SOLR-12635
             Project: Solr
          Issue Type: Improvement
      Security Level: Public (Default Security Level. Issues are Public)
            Reporter: Varun Thacker
            Assignee: Varun Thacker


I was doing some performance benchmarking for a user on slow streaming queries

The weird thing was that same streaming expression was fast when we fired it again

We were able to isolate the slowness to hash query parser

Here is the first and second time we fired the query - to simplify things this is for one shard and for the same worker
{code:java}
path=/export params={q=*:*&distrib=false&indent=off&fl=fields&fq=user:1&fq={!hash workers=6 worker=3}&partitionKeys=partitionKey&sort=partitionKey asc&wt=javabin&version=2.2} hits=0 status=0 QTime=6821

path=/export params={q=*:*&distrib=false&indent=off&fl=fields&fq=user:1&fq={!hash workers=6 worker=3}&partitionKeys=partitionKey&sort=partitionKey asc&wt=javabin&version=2.2} hits=0 status=0 QTime=0{code}
Even with hits=0 the first query took 6.8 seconds. The shard has 17m documents 

The second query utilizes the queryResultCache and hence it's lightening fast the second time around.

When we execute the same query and add a cost i.e {{&fq={!hash workers=6 worker=3}} cost=101} the query get's executed as a post filter and even uncashed is super fast.

I created this Jira so that we can always set cost > 100 from the parallel stream.

However I am happy to change the default behaviour for HashQParserPlugin and make it run as a post filter always unless explicitly specified. CollapsingQParserPlugin does this currently to make sure it's run as a post filter by default
{code:java}
public int getCost() {
  return Math.max(super.getCost(), 100);
}{code}
Thoughts anyone? 

 



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