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From Shawn Heisey <apa...@elyograg.org>
Subject Re: Solr 7.6.0: PingRequestHandler - Changing the default query (*:*)
Date Mon, 05 Aug 2019 12:58:01 GMT
On 8/4/2019 10:15 PM, dinesh naik wrote:
> My question is regarding the custom query being used. Here i am querying
> for field _root_ which is available in all of my cluster and defined as a
> string field. The result for _root_:abc might not get me any match as
> well(i am ok with not finding any matches, the query should not be taking
> 10-15 seconds for getting the response).

Typically the *:* query is the fastest option.  It is special syntax 
that means "all documents" and it usually executes very quickly.  It 
will be faster than querying for a value in a specific field, which is 
what you have defined currently.

I will typically add a "rows" parameter to the ping handler with a value 
of 1, so Solr will not be retrieving a large amount of data.  If you are 
running Solr in cloud mode, you should experiment with setting the 
distrib parameter to false, which will hopefully limit the query to the 
receiving node only.

Erick has already mentioned GC pauses as a potential problem.  With a 
10-15 second response time, I think that has high potential to be the 
underlying cause.

The response you included at the beginning of the thread indicates there 
are 1.3 billion documents, which is going to require a fair amount of 
heap memory.  If seeing such long ping times with a *:* query is 
something that happens frequently, your heap may be too small, which 
will cause frequent full garbage collections.

The very low autoSoftCommit time can contribute to system load.  I think 
it's very likely, especially with such a large index, that in many cases 
those automatic commits are taking far longer than 5 seconds to 
complete.  If that's the case, you're not achieving a 5 second 
visibility interval and you are putting a lot of load on Solr, so I 
would consider increasing it.

Thanks,
Shawn

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