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https://issues.apache.org/jira/browse/PHOENIX-258?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15388655#comment-15388655
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Mujtaba Chohan commented on PHOENIX-258:
----------------------------------------
[~lhofhansl] Tested on a table with 300M rows 230GB split in 78 regions on 16
node cluster. {{SELECT DISTINCT ORGANIZATION_ID FROM T}} with 2 distinct values
for leading row key takes *90* seconds compared to 110 seconds for full scan
count * aggregation.
{code}
Explain for select distinct:
CLIENT 78-CHUNK PARALLEL 78-WAY FULL SCAN OVER T
SERVER FILTER BY FIRST KEY ONLY
SERVER DISTINCT PREFIX FILTER OVER ORGANIZATION_ID
SERVER AGGREGATE INTO ORDERED DISTINCT ROWS BY ORGANIZATION_ID
CLIENT MERGE SORT
{code}
> Use skip scan when SELECT DISTINCT on leading row key column(s)
> ---------------------------------------------------------------
>
> Key: PHOENIX-258
> URL: https://issues.apache.org/jira/browse/PHOENIX-258
> Project: Phoenix
> Issue Type: Task
> Reporter: ryang-sfdc
> Assignee: Lars Hofhansl
> Fix For: 4.8.0
>
> Attachments: 258-WIP.txt, 258-v1.txt, 258-v10.txt, 258-v11.txt,
> 258-v12.txt, 258-v13.txt, 258-v14.txt, 258-v15.txt, 258-v16.txt, 258-v17.txt,
> 258-v2.txt, 258-v3.txt, 258-v4.txt, 258-v5.txt, 258-v6.txt, 258-v7.txt,
> 258-v8.txt, 258-v9.txt, 258.txt, DistinctFixedPrefixFilter.java, in-clause.png
>
>
> create table(a varchar(32) not null, date date not null constraint pk primary
> key(a,date))
> [["PLAN"],["CLIENT PARALLEL 94-WAY FULL SCAN OVER foo"],[" SERVER
> AGGREGATE INTO ORDERED DISTINCT ROWS BY [a]"],["CLIENT MERGE SORT"]]
>
> We should skip scan.
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