[ 
https://issues.apache.org/jira/browse/LUCENE-7976?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16513252#comment-16513252
 ] 

Lucene/Solr QA commented on LUCENE-7976:
----------------------------------------

| (x) *{color:red}-1 overall{color}* |
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|| Vote || Subsystem || Runtime || Comment ||
|| || || || {color:brown} Prechecks {color} ||
| {color:green}+1{color} | {color:green} test4tests {color} | {color:green}  0m 
 0s{color} | {color:green} The patch appears to include 1 new or modified test 
files. {color} |
|| || || || {color:brown} master Compile Tests {color} ||
| {color:green}+1{color} | {color:green} compile {color} | {color:green}  7m 
27s{color} | {color:green} master passed {color} |
|| || || || {color:brown} Patch Compile Tests {color} ||
| {color:green}+1{color} | {color:green} compile {color} | {color:green}  6m 
58s{color} | {color:green} the patch passed {color} |
| {color:red}-1{color} | {color:red} javac {color} | {color:red}  1m 49s{color} 
| {color:red} lucene_core generated 3 new + 1 unchanged - 0 fixed = 4 total 
(was 1) {color} |
| {color:green}+1{color} | {color:green} Release audit (RAT) {color} | 
{color:green}  2m 27s{color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} Check forbidden APIs {color} | 
{color:green}  1m 49s{color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} Validate source patterns {color} | 
{color:green}  1m 49s{color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} Validate ref guide {color} | 
{color:green}  1m 49s{color} | {color:green} the patch passed {color} |
|| || || || {color:brown} Other Tests {color} ||
| {color:green}+1{color} | {color:green} unit {color} | {color:green} 43m 
49s{color} | {color:green} core in the patch passed. {color} |
| {color:red}-1{color} | {color:red} unit {color} | {color:red} 65m 50s{color} 
| {color:red} core in the patch failed. {color} |
| {color:red}-1{color} | {color:red} unit {color} | {color:red} 13m 31s{color} 
| {color:red} solrj in the patch failed. {color} |
| {color:black}{color} | {color:black} {color} | {color:black}148m 29s{color} | 
{color:black} {color} |
\\
\\
|| Reason || Tests ||
| Failed junit tests | solr.rest.TestManagedResourceStorage |
|   | solr.cloud.autoscaling.SearchRateTriggerIntegrationTest |
|   | solr.cloud.autoscaling.ScheduledMaintenanceTriggerTest |
|   | solr.client.solrj.impl.CloudSolrClientTest |
|   | solr.common.util.TestJsonRecordReader |
\\
\\
|| Subsystem || Report/Notes ||
| JIRA Issue | LUCENE-7976 |
| JIRA Patch URL | 
https://issues.apache.org/jira/secure/attachment/12927680/LUCENE-7976.patch |
| Optional Tests |  compile  javac  unit  ratsources  checkforbiddenapis  
validatesourcepatterns  validaterefguide  |
| uname | Linux lucene2-us-west.apache.org 4.4.0-112-generic #135-Ubuntu SMP 
Fri Jan 19 11:48:36 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux |
| Build tool | ant |
| Personality | 
/home/jenkins/jenkins-slave/workspace/PreCommit-LUCENE-Build/sourcedir/dev-tools/test-patch/lucene-solr-yetus-personality.sh
 |
| git revision | master / 2db2fb3 |
| ant | version: Apache Ant(TM) version 1.9.6 compiled on July 8 2015 |
| Default Java | 1.8.0_172 |
| javac | 
https://builds.apache.org/job/PreCommit-LUCENE-Build/33/artifact/out/diff-compile-javac-lucene_core.txt
 |
| unit | 
https://builds.apache.org/job/PreCommit-LUCENE-Build/33/artifact/out/patch-unit-solr_core.txt
 |
| unit | 
https://builds.apache.org/job/PreCommit-LUCENE-Build/33/artifact/out/patch-unit-solr_solrj.txt
 |
|  Test Results | 
https://builds.apache.org/job/PreCommit-LUCENE-Build/33/testReport/ |
| modules | C: lucene/core solr/core solr/solrj solr/solr-ref-guide solr/webapp 
U: . |
| Console output | 
https://builds.apache.org/job/PreCommit-LUCENE-Build/33/console |
| Powered by | Apache Yetus 0.7.0   http://yetus.apache.org |


This message was automatically generated.



> Make TieredMergePolicy respect maxSegmentSizeMB and allow singleton merges of 
> very large segments
> -------------------------------------------------------------------------------------------------
>
>                 Key: LUCENE-7976
>                 URL: https://issues.apache.org/jira/browse/LUCENE-7976
>             Project: Lucene - Core
>          Issue Type: Improvement
>            Reporter: Erick Erickson
>            Assignee: Erick Erickson
>            Priority: Major
>         Attachments: LUCENE-7976.patch, LUCENE-7976.patch, LUCENE-7976.patch, 
> LUCENE-7976.patch, LUCENE-7976.patch, LUCENE-7976.patch, LUCENE-7976.patch, 
> LUCENE-7976.patch, LUCENE-7976.patch, LUCENE-7976.patch, LUCENE-7976.patch, 
> LUCENE-7976.patch, SOLR-7976.patch
>
>
> We're seeing situations "in the wild" where there are very large indexes (on 
> disk) handled quite easily in a single Lucene index. This is particularly 
> true as features like docValues move data into MMapDirectory space. The 
> current TMP algorithm allows on the order of 50% deleted documents as per a 
> dev list conversation with Mike McCandless (and his blog here:  
> https://www.elastic.co/blog/lucenes-handling-of-deleted-documents).
> Especially in the current era of very large indexes in aggregate, (think many 
> TB) solutions like "you need to distribute your collection over more shards" 
> become very costly. Additionally, the tempting "optimize" button exacerbates 
> the issue since once you form, say, a 100G segment (by 
> optimizing/forceMerging) it is not eligible for merging until 97.5G of the 
> docs in it are deleted (current default 5G max segment size).
> The proposal here would be to add a new parameter to TMP, something like 
> <maxAllowedPctDeletedInBigSegments> (no, that's not serious name, suggestions 
> welcome) which would default to 100 (or the same behavior we have now).
> So if I set this parameter to, say, 20%, and the max segment size stays at 
> 5G, the following would happen when segments were selected for merging:
> > any segment with > 20% deleted documents would be merged or rewritten NO 
> > MATTER HOW LARGE. There are two cases,
> >> the segment has < 5G "live" docs. In that case it would be merged with 
> >> smaller segments to bring the resulting segment up to 5G. If no smaller 
> >> segments exist, it would just be rewritten
> >> The segment has > 5G "live" docs (the result of a forceMerge or optimize). 
> >> It would be rewritten into a single segment removing all deleted docs no 
> >> matter how big it is to start. The 100G example above would be rewritten 
> >> to an 80G segment for instance.
> Of course this would lead to potentially much more I/O which is why the 
> default would be the same behavior we see now. As it stands now, though, 
> there's no way to recover from an optimize/forceMerge except to re-index from 
> scratch. We routinely see 200G-300G Lucene indexes at this point "in the 
> wild" with 10s of  shards replicated 3 or more times. And that doesn't even 
> include having these over HDFS.
> Alternatives welcome! Something like the above seems minimally invasive. A 
> new merge policy is certainly an alternative.



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