Mujtaba Chohan created PHOENIX-2943:
---------------------------------------
Summary: Performance of parallel group 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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