phoenix-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Gerald Sangudi (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (PHOENIX-4751) Support client-side hash aggregation with SORT_MERGE_JOIN
Date Mon, 02 Jul 2018 20:52:00 GMT

    [ https://issues.apache.org/jira/browse/PHOENIX-4751?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16530425#comment-16530425
] 

Gerald Sangudi edited comment on PHOENIX-4751 at 7/2/18 8:51 PM:
-----------------------------------------------------------------

Ready for review. Pull request https://github.com/apache/phoenix/pull/308

The hashing is done in memory, instead of using SpillableGroupByCache. This is consistent
with the current client-side in-memory sort, and avoids any dependencies in SpillableGroupByCache.



was (Author: sangudi):
Ready for review. Pull request https://github.com/apache/phoenix/pull/308


> Support client-side hash aggregation with SORT_MERGE_JOIN
> ---------------------------------------------------------
>
>                 Key: PHOENIX-4751
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-4751
>             Project: Phoenix
>          Issue Type: Improvement
>    Affects Versions: 4.14.0, 4.13.1
>            Reporter: Gerald Sangudi
>            Priority: Major
>
> A GROUP BY that follows a SORT_MERGE_JOIN should be able to use hash aggregation in
some cases, for improved performance.
> When a GROUP BY follows a SORT_MERGE_JOIN, the GROUP BY does not use hash aggregation.
It instead performs a CLIENT SORT followed by a CLIENT AGGREGATE. The performance can be
improved if (a) the GROUP BY output does not need to be sorted, and (b) the GROUP BY input is
large enough and has low cardinality.
> The hash aggregation can initially be a hint. Here is an example from Phoenix 4.13.1
that would benefit from hash aggregation if the GROUP BY input is large with low cardinality.
> CREATE TABLE unsalted (
>  keyA BIGINT NOT NULL,
>  keyB BIGINT NOT NULL,
>  val SMALLINT,
>  CONSTRAINT pk PRIMARY KEY (keyA, keyB)
>  );
> EXPLAIN
>  SELECT /*+ USE_SORT_MERGE_JOIN */ 
>  t1.val v1, t2.val v2, COUNT(\*) c 
>  FROM unsalted t1 JOIN unsalted t2 
>  ON (t1.keyA = t2.keyA) 
>  GROUP BY t1.val, t2.val;
>  +-------------------------------------------------------------+----------------++------------------+
> |PLAN|EST_BYTES_READ|EST_ROWS_READ| |
> +-------------------------------------------------------------+----------------++------------------+
> |SORT-MERGE-JOIN (INNER) TABLES|null|null| |
> |    CLIENT 1-CHUNK PARALLEL 1-WAY FULL SCAN OVER UNSALTED|null|null| |
> |AND|null|null| |
> |    CLIENT 1-CHUNK PARALLEL 1-WAY FULL SCAN OVER UNSALTED|null|null| |
> |CLIENT SORTED BY [TO_DECIMAL(T1.VAL), T2.VAL]|null|null| |
> |CLIENT AGGREGATE INTO DISTINCT ROWS BY [T1.VAL, T2.VAL]|null|null| |
> +-------------------------------------------------------------+----------------++------------------+



--
This message was sent by Atlassian JIRA
(v7.6.3#76005)

Mime
View raw message