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https://issues.apache.org/jira/browse/PHOENIX-3023?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15351516#comment-15351516
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Hudson commented on PHOENIX-3023:
---------------------------------
FAILURE: Integrated in Phoenix-master #1294 (See
[https://builds.apache.org/job/Phoenix-master/1294/])
PHOENIX-3023 Slow performance when limit queries are executed in (samarth: rev
9078dddc88d8749016ace2d94da7f7dd54eeff96)
* phoenix-core/src/main/java/org/apache/phoenix/execute/AggregatePlan.java
* phoenix-core/src/main/java/org/apache/phoenix/iterate/TableResultIterator.java
* phoenix-core/src/main/java/org/apache/phoenix/util/ScanUtil.java
* phoenix-core/src/main/java/org/apache/phoenix/iterate/ParallelIterators.java
* phoenix-core/src/main/java/org/apache/phoenix/iterate/BaseResultIterators.java
* phoenix-core/src/main/java/org/apache/phoenix/execute/ScanPlan.java
*
phoenix-core/src/test/java/org/apache/phoenix/query/ParallelIteratorsSplitTest.java
*
phoenix-core/src/test/java/org/apache/phoenix/compile/StatementHintsCompilationTest.java
> Slow performance when limit queries are executed in parallel by default
> -----------------------------------------------------------------------
>
> Key: PHOENIX-3023
> URL: https://issues.apache.org/jira/browse/PHOENIX-3023
> Project: Phoenix
> Issue Type: Bug
> Affects Versions: 4.8.0
> Reporter: Mujtaba Chohan
> Assignee: Samarth Jain
> Fix For: 4.8.0
>
> Attachments: PHOENIX-3023.patch, PHOENIX-3023_v2.patch
>
>
> After
> [this|https://git-wip-us.apache.org/repos/asf?p=phoenix.git;a=commit;h=54362430d71be788d515944573572624628a09b6]
> commit, limit queries are executed in parallel which causes performance to
> be ~5-10x slower. Providing a serial hint fixes it though.
> After commit:
> {code}
> select * from WIDE_PK order by mypk DESC limit 1; // this takes ~400ms
> CLIENT 1280-CHUNK 1996304 ROWS 6380181208 BYTES PARALLEL 4-WAY REVERSE FULL
> SCAN OVER WIDE_PK SERVER 1 ROW LIMIT CLIENT MERGE SORT CLIENT 1 ROW LIMIT
> {code}
> Before commit:
> {code}
> select * from WIDE_PK order by mypk DESC limit 1; // this takes ~40ms
> CLIENT 1280-CHUNK 1996304 ROWS 6380181208 BYTES SERIAL 4-WAY REVERSE FULL
> SCAN OVER WIDE_PK SERVER 1 ROW LIMIT CLIENT MERGE SORT CLIENT 1 ROW LIMIT
> {code}
> Test was done on a single node machine running HBase 0.98.17. DDL used was
> {code}CREATE TABLE WIDE_PK (MYPK CHAR(500) NOT NULL PRIMARY KEY,CF.column1
> INTEGER,CF.column2 INTEGER,CF.column3 INTEGER,CF.column4 INTEGER,CF.column5
> INTEGER) SALT_BUCKETS=4 with phoenix.stats.guidepost.width of 5000000
> {code}
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