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From "Mujtaba Chohan (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (PHOENIX-4287) Incorrect aggregate query results when stats are disable for parallelization
Date Thu, 02 Nov 2017 20:02:01 GMT

    [ https://issues.apache.org/jira/browse/PHOENIX-4287?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16236498#comment-16236498
] 

Mujtaba Chohan commented on PHOENIX-4287:
-----------------------------------------

Just figured that out as well :) That index was created with previous version and it had {{USE_STATS_FOR_PARALLELIZATION}}
set to true causing index to use parallelization. 

Here's a case that still doesn't work with table created with latest version:
Global {{USE_STATS_FOR_PARALLELIZATION}} is set to *false*.
Table and global index created without setting parallelization.
Table parallelization is set to *true* ALTER ...SET USE_STATS_FOR_PARALLELIZATION=true. Verified
in SYSTEM.CATALOG as well as it is set for base table only.
Parallelization is *not* used for queries when they get executed against *index*, parallelization
is correctly used for base table.




> Incorrect aggregate query results when stats are disable for parallelization
> ----------------------------------------------------------------------------
>
>                 Key: PHOENIX-4287
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-4287
>             Project: Phoenix
>          Issue Type: Bug
>    Affects Versions: 4.12.0
>         Environment: HBase 1.3.1
>            Reporter: Mujtaba Chohan
>            Assignee: Samarth Jain
>            Priority: Major
>              Labels: localIndex
>             Fix For: 4.13.0, 4.12.1
>
>         Attachments: PHOENIX-4287.patch, PHOENIX-4287_addendum.patch, PHOENIX-4287_addendum2.patch,
PHOENIX-4287_addendum3.patch, PHOENIX-4287_addendum4.patch, PHOENIX-4287_v2.patch, PHOENIX-4287_v3.patch,
PHOENIX-4287_v3_wip.patch, PHOENIX-4287_v4.patch
>
>
> With {{phoenix.use.stats.parallelization}} set to {{false}}, aggregate query returns
incorrect results when stats are available.
> With local index and stats disabled for parallelization:
> {noformat}
> explain select count(*) from TABLE_T;
> +-------------------------------------------------------------------------------------------------------+-----------------+----------------+-----------+
> |                                                 PLAN                              
                   | EST_BYTES_READ  | EST_ROWS_READ  |  EST_INFO |
> +-------------------------------------------------------------------------------------------------------+-----------------+----------------+-----------+
> | CLIENT 0-CHUNK 332170 ROWS 625043899 BYTES PARALLEL 0-WAY RANGE SCAN OVER TABLE_T [1]
 | 625043899       | 332170         | 150792825 |
> |     SERVER FILTER BY FIRST KEY ONLY                                               
                   | 625043899       | 332170         | 150792825 |
> |     SERVER AGGREGATE INTO SINGLE ROW                                              
                   | 625043899       | 332170         | 150792825 |
> +-------------------------------------------------------------------------------------------------------+-----------------+----------------+-----------+
> select count(*) from TABLE_T;
> +-----------+
> | COUNT(1)  |
> +-----------+
> | 0         |
> +-----------+
> {noformat}
> Using data table
> {noformat}
> explain select /*+NO_INDEX*/ count(*) from TABLE_T;
> +--------------------------------------------------------------------------------------------------+-----------------+----------------+----------------+
> |                                               PLAN                                
              | EST_BYTES_READ  | EST_ROWS_READ  |  EST_INFO_TS   |
> +--------------------------------------------------------------------------------------------------+-----------------+----------------+----------------+
> | CLIENT 2-CHUNK 332151 ROWS 438492470 BYTES PARALLEL 1-WAY FULL SCAN OVER TABLE_T  |
438492470       | 332151         | 1507928257617  |
> |     SERVER FILTER BY FIRST KEY ONLY                                               
              | 438492470       | 332151         | 1507928257617  |
> |     SERVER AGGREGATE INTO SINGLE ROW                                              
              | 438492470       | 332151         | 1507928257617  |
> +--------------------------------------------------------------------------------------------------+-----------------+----------------+----------------+
> select /*+NO_INDEX*/ count(*) from TABLE_T;
> +-----------+
> | COUNT(1)  |
> +-----------+
> | 14        |
> +-----------+
> {noformat}
> Without stats available, results are correct:
> {noformat}
> explain select /*+NO_INDEX*/ count(*) from TABLE_T;
> +----------------------------------------------------------------------+-----------------+----------------+--------------+
> |                                 PLAN                                 | EST_BYTES_READ
 | EST_ROWS_READ  | EST_INFO_TS  |
> +----------------------------------------------------------------------+-----------------+----------------+--------------+
> | CLIENT 2-CHUNK PARALLEL 1-WAY FULL SCAN OVER TABLE_T  | null            | null    
      | null         |
> |     SERVER FILTER BY FIRST KEY ONLY                                  | null       
    | null           | null         |
> |     SERVER AGGREGATE INTO SINGLE ROW                                 | null       
    | null           | null         |
> +----------------------------------------------------------------------+-----------------+----------------+--------------+
> select /*+NO_INDEX*/ count(*) from TABLE_T;
> +-----------+
> | COUNT(1)  |
> +-----------+
> | 333327    |
> +-----------+
> {noformat}



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