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https://issues.apache.org/jira/browse/PHOENIX-2943?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15308359#comment-15308359
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Mujtaba Chohan commented on PHOENIX-2943:
-----------------------------------------
[~jamestaylor] Not a regression as query results are incorrect in 4.7.0 as well
PHOENIX-2942
[~samarthjain] [[email protected]]
* Performance of serial query got significantly better in current 4.8 snapshot
head compared to 4.7.0 as Ankit mentions it seem like it's getting those values
from first chunk.
* Results are incorrect for *both* parallel and serial execution
{code}
select L_DISCOUNT, L_QUANTITY from lineitem_encoded order by
(l_discount,L_QUANTITY) DESC limit 1;
+-------------+-------------+
| L_DISCOUNT | L_QUANTITY |
+-------------+-------------+
| 0.04 | 17 |
+-------------+-------------+
select L_DISCOUNT, L_QUANTITY from lineitem_encoded order by
(l_discount,L_QUANTITY) ASC limit 1;
+-------------+-------------+
| L_DISCOUNT | L_QUANTITY |
+-------------+-------------+
| 0.04 | 17 |
+-------------+-------------+
select L_DISCOUNT, L_QUANTITY from lineitem_encoded order by (l_discount) ASC
limit 1;
+-------------+-------------+
| L_DISCOUNT | L_QUANTITY |
+-------------+-------------+
| 0 | 38 |
+-------------+-------------+
select L_DISCOUNT, L_QUANTITY from lineitem_encoded order by (l_discount) DESC
limit 1;
+-------------+-------------+
| L_DISCOUNT | L_QUANTITY |
+-------------+-------------+
| 0.1 | 8 |
+-------------+-------------+
{code}
Without stats serial query is almost as slow as running in parallel over 2
regions. Results are incorrect with/without stats. Tested the above with both
HBase 0.98.12 and 0.98.17
> Performance of parallel order by query is > 30X slower than serial execution
> ----------------------------------------------------------------------------
>
> Key: PHOENIX-2943
> URL: https://issues.apache.org/jira/browse/PHOENIX-2943
> Project: Phoenix
> Issue Type: Bug
> Reporter: Mujtaba Chohan
> Fix For: 4.8.0
>
>
> {code}
> select /*+SERIAL*/ L_DISCOUNT, L_QUANTITY from lineitem_encoded order by
> (l_discount,L_QUANTITY) limit 1;
> +-------------+-------------+
> | L_DISCOUNT | L_QUANTITY |
> +-------------+-------------+
> | 0.04 | 17 |
> +-------------+-------------+
> 1 row selected (0.129 seconds)
> select L_DISCOUNT, L_QUANTITY from lineitem_encoded order by
> (l_discount,L_QUANTITY) limit 1;
> +-------------+-------------+
> | L_DISCOUNT | L_QUANTITY |
> +-------------+-------------+
> | 0.04 | 17 |
> +-------------+-------------+
> 1 row selected (4.63 seconds)
> explain select /*+SERIAL*/ L_DISCOUNT, L_QUANTITY from lineitem_encoded
> order by (l_discount,L_QUANTITY) limit 1;
> +------------------------------------------------------------------------------------------------+
> | PLAN
> |
> +------------------------------------------------------------------------------------------------+
> | CLIENT 417-CHUNK 5978838 ROWS 4150009682 BYTES SERIAL 417-WAY FULL SCAN
> OVER LINEITEM_ENCODED |
> | SERVER TOP 1 ROW SORTED BY [(L_DISCOUNT, L_QUANTITY)]
> |
> | CLIENT MERGE SORT
> |
> +------------------------------------------------------------------------------------------------+
> 3 rows selected (0.016 seconds)
> 0: jdbc:phoenix:localhost> explain select L_DISCOUNT, L_QUANTITY from
> lineitem_encoded order by (l_discount,L_QUANTITY) limit 1;
> +--------------------------------------------------------------------------------------------------+
> | PLAN
> |
> +--------------------------------------------------------------------------------------------------+
> | CLIENT 417-CHUNK 5978838 ROWS 4150009682 BYTES PARALLEL 417-WAY FULL SCAN
> OVER LINEITEM_ENCODED |
> | SERVER TOP 1 ROW SORTED BY [(L_DISCOUNT, L_QUANTITY)]
> |
> | CLIENT MERGE SORT
> |
> +--------------------------------------------------------------------------------------------------+
> 3 rows selected (0.015 seconds)
> {code}
> Profiler information on this to be added soon.
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