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https://issues.apache.org/jira/browse/SOLR-14298?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17442131#comment-17442131
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Dinesh Kumar Naik commented on SOLR-14298:
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[~hossman] I completely agree with you. Doing a match-all query with billions
of documents per shard can be a very costly operation even though the row is
set to 0 with distrib false.
Here are some of the calls and their respective QTime from one of my setup :
{code:java}
2021-11-09 21:15:53.853 WARN (qtp435914790-25301965)
x:Item_collection_shard15_replica_n115 o.a.s.c.S.SlowRequest slow:
[Item_collection_shard15_replica_n115] webapp=/solr path=/select
params={q=*:*&distrib=false&sort=_docid_+asc&rows=0&wt=javabin&version=2}
hits=1226420962 status=0 QTime=15516
2021-11-10 00:45:16.816 WARN (qtp435914790-25341761)
x:Item_collection_shard15_replica_n115 o.a.s.c.S.SlowRequest slow:
[Item_collection_shard15_replica_n115] webapp=/solr path=/select
params={q=*:*&distrib=false&sort=_docid_+asc&rows=0&wt=javabin&version=2}
hits=1226984671 status=0 QTime=15169
2021-11-10 00:45:30.772 WARN (qtp435914790-25339675)
x:Item_collection_shard15_replica_n115 o.a.s.c.S.SlowRequest slow:
[Item_collection_shard15_replica_n115] webapp=/solr path=/select
params={q=*:*&distrib=false&sort=_docid_+asc&rows=0&wt=javabin&version=2}
hits=1226985078 status=0 QTime=15494
2021-11-10 00:45:34.244 WARN (qtp435914790-25334052)
x:Item_collection_shard15_replica_n115 o.a.s.c.S.SlowRequest slow:
[Item_collection_shard15_replica_n115] webapp=/solr path=/select
params={q=*:*&distrib=false&sort=_docid_+asc&rows=0&wt=javabin&version=2}
hits=1226985527 status=0 QTime=15462
2021-11-10 00:46:19.480 WARN (qtp435914790-25340369)
x:Item_collection_shard15_replica_n115 o.a.s.c.S.SlowRequest slow:
[Item_collection_shard15_replica_n115] webapp=/solr path=/select
params={q=*:*&distrib=false&sort=_docid_+asc&rows=0&wt=javabin&version=2}
hits=1226987732 status=0 QTime=14553
2021-11-10 18:03:49.885 WARN (qtp435914790-25486769)
x:Item_collection_shard15_replica_n115 o.a.s.c.S.SlowRequest slow:
[Item_collection_shard15_replica_n115] webapp=/solr path=/select
params={q=*:*&distrib=false&sort=_docid_+asc&rows=0&wt=javabin&version=2}
hits=1228021741 status=0 QTime=16130
2021-11-10 18:04:14.511 WARN (qtp435914790-25523411)
x:Item_collection_shard15_replica_n115 o.a.s.c.S.SlowRequest slow:
[Item_collection_shard15_replica_n115] webapp=/solr path=/select
params={q=*:*&distrib=false&sort=_docid_+asc&rows=0&wt=javabin&version=2}
hits=1228021262 status=0 QTime=16626
2021-11-10 18:04:23.904 WARN (qtp435914790-25454090)
x:Item_collection_shard15_replica_n115 o.a.s.c.S.SlowRequest slow:
[Item_collection_shard15_replica_n115] webapp=/solr path=/select
params={q=*:*&distrib=false&sort=_docid_+asc&rows=0&wt=javabin&version=2}
hits=1228020775 status=0 QTime=16556
2021-11-10 18:04:43.355 WARN (qtp435914790-25505322)
x:Item_collection_shard15_replica_n115 o.a.s.c.S.SlowRequest slow:
[Item_collection_shard15_replica_n115] webapp=/solr path=/select
params={q=*:*&distrib=false&sort=_docid_+asc&rows=0&wt=javabin&version=2}
hits=1228020627 status=0 QTime=17029
2021-11-10 18:04:49.181 WARN (qtp435914790-25509646)
x:Item_collection_shard15_replica_n115 o.a.s.c.S.SlowRequest slow:
[Item_collection_shard15_replica_n115] webapp=/solr path=/select
params={q=*:*&distrib=false&sort=_docid_+asc&rows=0&wt=javabin&version=2}
hits=1228020577 status=0 QTime=17242
2021-11-10 18:04:53.577 WARN (qtp435914790-25484919)
x:Item_collection_shard15_replica_n115 o.a.s.c.S.SlowRequest slow:
[Item_collection_shard15_replica_n115] webapp=/solr path=/select
params={q=*:*&distrib=false&sort=_docid_+asc&rows=0&wt=javabin&version=2}
hits=1228020577 status=0 QTime=19169
2021-11-10 18:05:06.366 WARN (qtp435914790-25523409)
x:Item_collection_shard15_replica_n115 o.a.s.c.S.SlowRequest slow:
[Item_collection_shard15_replica_n115] webapp=/solr path=/select
params={q=*:*&distrib=false&sort=_docid_+asc&rows=0&wt=javabin&version=2}
hits=1228019443 status=0 QTime=17352
2021-11-10 18:05:07.594 WARN (qtp435914790-25527485)
x:Item_collection_shard15_replica_n115 o.a.s.c.S.SlowRequest slow:
[Item_collection_shard15_replica_n115] webapp=/solr path=/select
params={q=*:*&distrib=false&sort=_docid_+asc&rows=0&wt=javabin&version=2}
hits=1228018445 status=0 QTime=17309
2021-11-10 18:05:07.908 WARN (qtp435914790-25496685)
x:Item_collection_shard15_replica_n115 o.a.s.c.S.SlowRequest slow:
[Item_collection_shard15_replica_n115] webapp=/solr path=/select
params={q=*:*&distrib=false&sort=_docid_+asc&rows=0&wt=javabin&version=2}
hits=1228018445 status=0 QTime=17445 {code}
The QTime is over 14 , 15 seconds for all such checks which can be avoided as
you suggested.
Here is my observation for the 3 approaches suggested by you:
1. The *segmentTerminateEarly* option might not help us as the default merge
policy is *TieredMergePolicyFactory.*
As per
[https://solr.apache.org/guide/8_6/common-query-parameters.html#segmentterminateearly-parameter]
If *segmentTerminateEarly* is set to true, and if [the
mergePolicyFactory|https://solr.apache.org/guide/8_6/indexconfig-in-solrconfig.html#mergepolicyfactory]
for this collection is a
[SortingMergePolicyFactory|https://lucene.apache.org/solr/8_6_0/solr-core/org/apache/solr/index/SortingMergePolicyFactory.html]
which uses a sort option compatible with [the sort
parameter|https://solr.apache.org/guide/8_6/common-query-parameters.html#sort-parameter]
specified for this query, then Solr will be able to skip documents on a
per-segment basis that are definitively not candidates for the current page of
results.
2. Use of timeAllowed: Using the smaller value of timeAllowed helps reduce the
QTime Drastically and it would return partial results.
!image-2021-11-11-13-11-30-930.png|width=524,height=288!
3. Negation match all query ie. q=-*:*
This seems to be the fastest option and it would literally be a 1 character
patch.
!image-2021-11-11-13-13-20-791.png|width=524,height=267!
Kindly let me know your thoughts and then we can plan for a patch accordingly!
> LBSolrClient.checkAZombieServer should be less stupid
> -----------------------------------------------------
>
> Key: SOLR-14298
> URL: https://issues.apache.org/jira/browse/SOLR-14298
> Project: Solr
> Issue Type: Bug
> Reporter: Chris M. Hostetter
> Priority: Major
> Attachments: image-2021-11-11-13-11-30-930.png,
> image-2021-11-11-13-13-20-791.png
>
>
> LBSolrClient.checkAZombieServer() currently does /select query for {{\*:\*}}
> with distrib=false, rows=0, sort=\_docid\_ ... but this can still chew up a
> lot of time if the shard is big, and it's not self evident wtf is going on in
> the server logs.
> At a minimum, these requests should include some sort of tracing param to
> identify the point of he query (ie: {{_zombieservercheck=true}}) and should
> probably be changed to hit something like the /ping handler, or the node
> status handler, or if it's important to folks that it do a "search" that
> actaully uses the index searcher, then it should use options like
> timeAllowed / segmentTerminateEarly, and/or {{q=-\*:\*}} instead .. or maybe
> a cusorMark ... something to make it not have the overhead of counting all
> the hits.
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