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https://issues.apache.org/jira/browse/PHOENIX-3560?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15814497#comment-15814497
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Lars Hofhansl edited comment on PHOENIX-3560 at 1/11/17 6:03 AM:
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I think , if we set this to _1(greater than _0 EMPTY_COLUMN_NAME), queries
using FirstKeyOnlyFilter(like count\(*)) will read this empty KV only.
{code}
public static final String SINGLE_KEYVALUE_COLUMN_QUALIFIER = "_1";
{code}
was (Author: [email protected]):
I think , if we set this to _1(greater than _0 EMPTY_COLUMN_NAME), queries
using FirstKeyOnlyFilter(like count(*)) will read this empty KV only.
{code}
public static final String SINGLE_KEYVALUE_COLUMN_QUALIFIER = "_1";
{code}
> Aggregate query performance is worse with encoded columns for schema with
> large number of columns
> -------------------------------------------------------------------------------------------------
>
> Key: PHOENIX-3560
> URL: https://issues.apache.org/jira/browse/PHOENIX-3560
> Project: Phoenix
> Issue Type: Sub-task
> Reporter: Mujtaba Chohan
> Assignee: Samarth Jain
> Fix For: 4.10.0
>
> Attachments: DataGenerator.java, PHOENIX-3565.patch
>
>
> Schema with 5K columns
> {noformat}
> create table (k1 integer, k2 integer, c1 varchar ... c5000 varchar CONSTRAINT
> PK PRIMARY KEY (K1, K2))
> VERSIONS=1, MULTI_TENANT=true, IMMUTABLE_ROWS=true
> {noformat}
> In this test, there are no null columns and each column contains 200 chars
> i.e. 1MB of data per row.
> Count * aggregation is about 5X slower with encoded columns when compared to
> table non-encoded columns using the same schema.
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