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Date: Tue, 28 Feb 2017 15:26:45 +0000 (UTC)
From: "Hadoop QA (JIRA)" <jira@apache.org>
To: issues@hbase.apache.org
Message-ID: <JIRA.13043666.1487257052000.19110.1488295605310@Atlassian.JIRA>
In-Reply-To: <JIRA.13043666.1487257052000@Atlassian.JIRA>
References: <JIRA.13043666.1487257052000@Atlassian.JIRA> <JIRA.13043666.1487257052337@jira-lw-us.apache.org>
Subject: [jira] [Commented] (HBASE-17655) Removing MemStoreScanner and
 SnapshotScanner
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archived-at: Tue, 28 Feb 2017 15:26:52 -0000


    [ https://issues.apache.org/jira/browse/HBASE-17655?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15888204#comment-15888204 ] 

Hadoop QA commented on HBASE-17655:
-----------------------------------

| (/) *{color:green}+1 overall{color}* |
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|| Vote || Subsystem || Runtime || Comment ||
| {color:blue}0{color} | {color:blue} reexec {color} | {color:blue} 9m 58s {color} | {color:blue} Docker mode activated. {color} |
| {color:green}+1{color} | {color:green} hbaseanti {color} | {color:green} 0m 0s {color} | {color:green} Patch does not have any anti-patterns. {color} |
| {color:green}+1{color} | {color:green} @author {color} | {color:green} 0m 0s {color} | {color:green} The patch does not contain any @author tags. {color} |
| {color:green}+1{color} | {color:green} test4tests {color} | {color:green} 0m 0s {color} | {color:green} The patch appears to include 9 new or modified test files. {color} |
| {color:blue}0{color} | {color:blue} mvndep {color} | {color:blue} 0m 28s {color} | {color:blue} Maven dependency ordering for branch {color} |
| {color:green}+1{color} | {color:green} mvninstall {color} | {color:green} 3m 11s {color} | {color:green} master passed {color} |
| {color:green}+1{color} | {color:green} compile {color} | {color:green} 0m 49s {color} | {color:green} master passed {color} |
| {color:green}+1{color} | {color:green} checkstyle {color} | {color:green} 1m 33s {color} | {color:green} master passed {color} |
| {color:green}+1{color} | {color:green} mvneclipse {color} | {color:green} 0m 27s {color} | {color:green} master passed {color} |
| {color:green}+1{color} | {color:green} findbugs {color} | {color:green} 2m 5s {color} | {color:green} master passed {color} |
| {color:green}+1{color} | {color:green} javadoc {color} | {color:green} 0m 36s {color} | {color:green} master passed {color} |
| {color:blue}0{color} | {color:blue} mvndep {color} | {color:blue} 0m 11s {color} | {color:blue} Maven dependency ordering for patch {color} |
| {color:green}+1{color} | {color:green} mvninstall {color} | {color:green} 0m 55s {color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} compile {color} | {color:green} 0m 49s {color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} javac {color} | {color:green} 0m 49s {color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} checkstyle {color} | {color:green} 1m 33s {color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} mvneclipse {color} | {color:green} 0m 27s {color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} whitespace {color} | {color:green} 0m 0s {color} | {color:green} The patch has no whitespace issues. {color} |
| {color:green}+1{color} | {color:green} hadoopcheck {color} | {color:green} 27m 4s {color} | {color:green} Patch does not cause any errors with Hadoop 2.6.1 2.6.2 2.6.3 2.6.4 2.6.5 2.7.1 2.7.2 2.7.3 or 3.0.0-alpha2. {color} |
| {color:green}+1{color} | {color:green} findbugs {color} | {color:green} 2m 21s {color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} javadoc {color} | {color:green} 0m 36s {color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} unit {color} | {color:green} 93m 17s {color} | {color:green} hbase-server in the patch passed. {color} |
| {color:green}+1{color} | {color:green} unit {color} | {color:green} 0m 23s {color} | {color:green} hbase-examples in the patch passed. {color} |
| {color:green}+1{color} | {color:green} asflicense {color} | {color:green} 0m 28s {color} | {color:green} The patch does not generate ASF License warnings. {color} |
| {color:black}{color} | {color:black} {color} | {color:black} 147m 45s {color} | {color:black} {color} |
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|| Subsystem || Report/Notes ||
| Docker | Client=1.12.3 Server=1.12.3 Image:yetus/hbase:8d52d23 |
| JIRA Patch URL | https://issues.apache.org/jira/secure/attachment/12855144/HBASE-17655-V05.patch |
| JIRA Issue | HBASE-17655 |
| Optional Tests |  asflicense  javac  javadoc  unit  findbugs  hadoopcheck  hbaseanti  checkstyle  compile  |
| uname | Linux 708c02eec995 3.13.0-107-generic #154-Ubuntu SMP Tue Dec 20 09:57:27 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux |
| Build tool | maven |
| Personality | /home/jenkins/jenkins-slave/workspace/PreCommit-HBASE-Build/component/dev-support/hbase-personality.sh |
| git revision | master / f4e0ea2 |
| Default Java | 1.8.0_121 |
| findbugs | v3.0.0 |
|  Test Results | https://builds.apache.org/job/PreCommit-HBASE-Build/5874/testReport/ |
| modules | C: hbase-server hbase-examples U: . |
| Console output | https://builds.apache.org/job/PreCommit-HBASE-Build/5874/console |
| Powered by | Apache Yetus 0.3.0   http://yetus.apache.org |


This message was automatically generated.


> Removing MemStoreScanner and SnapshotScanner
> --------------------------------------------
>
>                 Key: HBASE-17655
>                 URL: https://issues.apache.org/jira/browse/HBASE-17655
>             Project: HBase
>          Issue Type: Improvement
>          Components: Scanners
>    Affects Versions: 2.0.0
>            Reporter: Eshcar Hillel
>            Assignee: Eshcar Hillel
>         Attachments: HBASE-17655-V01.patch, HBASE-17655-V02.patch, HBASE-17655-V03.patch, HBASE-17655-V04.patch, HBASE-17655-V05.patch, HBASE-17655-V05.patch
>
>
> With CompactingMemstore becoming the new default, a store comprises multiple memory segments and not just 1-2. MemStoreScanner encapsulates the scanning of segments in the memory part of the store. SnapshotScanner is used to scan the snapshot segment upon flush to disk.
> Having the logic of scanners scattered in multiple classes (StoreScanner, SegmentScanner, MemStoreScanner, SnapshotScanner) makes maintainance and debugging challenging tasks, not always for a good reason.
> For example, MemStoreScanner has a KeyValueHeap (KVH). When creating the store scanner which also has a KVH, this makes a KVH inside a KVH. Reasoning about the correctness of the methods supported by the scanner (seek, next, hasNext, peek, etc.) is hard and debugging  them is cumbersome. 
> In addition, by removing the MemStoreScanner layer we allow store scanner to filter out each one of the memory scanners instead of either taking them all (in most cases) or discarding them all (rarely).
> SnapshotScanner is a simplified version of SegmentScanner as it is used only in a specific context. However it is an additional implementation of the same logic with no real advantage of improved performance.
> Therefore, I suggest removing both MemStoreScanner and SnapshotScanner. The code is adjusted to handle the list of segment scanners they encapsulate.
> This fits well with the current code since in most cases at some point a list of scanner is expected, so passing the actual list of segment scanners is more natural than wrapping a single (high level) scanner with Collections.singeltonList(...).


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