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Posted to dev@trafodion.apache.org by "Liu, Yuan (Yuan)" <yu...@esgyn.cn> on 2018/11/09 00:56:13 UTC
What does (m) mean in esp_exchange
Hi Trafodioneers,
I get a query plan below, can anyone teach me what does the (m) mean in red box? Thanks ahead.
[cid:image001.png@01D47809.FED29780]
Best regards
Yuan
RE: What does (m) mean in esp_exchange
Posted by Selva Govindarajan <se...@esgyn.com>.
'm' in the esp_exchange means that this esp acts like merge esp exchange. The tuple producers provides the tuples in the sorted order of the chosen key. Then the exchange operator can pick the rows in the sorted order from the producers and project the sorted rows to its parent.
Selva
-----Original Message-----
From: Liu, Yuan (Yuan) <yu...@esgyn.cn>
Sent: Thursday, November 8, 2018 4:58 PM
To: dev@trafodion.apache.org
Subject: RE: What does (m) mean in esp_exchange
Sorry, in case you can not see the screenshot, just paste the query plan as below.
SQL>explain options 'f' select stat_mon_year,count(*) from (
select stat_mon_year,stat_mon,count(*) from DMA_ENTTYPE_STAT group by 1,2) a group by 1;+>
LC RC OP OPERATOR OPT DESCRIPTION CARD
---- ---- ---- -------------------- -------- -------------------- ---------
7 . 8 root 6.00E+000
6 . 7 hash_partial_groupby 6.00E+000
5 . 6 esp_exchange 1:6(hash2) (m) 6.00E+000
4 . 5 hash_partial_groupby 6.00E+000
3 . 4 hash_partial_groupby 4.07E+002
2 . 3 esp_exchange 6(hash2):8(hash2) 4.07E+002
1 . 2 hash_partial_groupby 4.07E+002
. . 1 trafodion_scan DMA_ENTTYPE_STAT 5.03E+006
--- SQL operation complete.
Best regards
Yuan
From: Liu, Yuan (Yuan) <yu...@esgyn.cn>
Sent: Friday, November 09, 2018 8:56 AM
To: dev@trafodion.apache.org
Subject: What does (m) mean in esp_exchange
Hi Trafodioneers,
I get a query plan below, can anyone teach me what does the (m) mean in red box? Thanks ahead.
[cid:image001.png@01D47809.FED29780]
Best regards
Yuan
RE: What does (m) mean in esp_exchange
Posted by "Liu, Yuan (Yuan)" <yu...@esgyn.cn>.
Sorry, in case you can not see the screenshot, just paste the query plan as below.
SQL>explain options 'f' select stat_mon_year,count(*) from (
select stat_mon_year,stat_mon,count(*) from DMA_ENTTYPE_STAT group by 1,2) a group by 1;+>
LC RC OP OPERATOR OPT DESCRIPTION CARD
---- ---- ---- -------------------- -------- -------------------- ---------
7 . 8 root 6.00E+000
6 . 7 hash_partial_groupby 6.00E+000
5 . 6 esp_exchange 1:6(hash2) (m) 6.00E+000
4 . 5 hash_partial_groupby 6.00E+000
3 . 4 hash_partial_groupby 4.07E+002
2 . 3 esp_exchange 6(hash2):8(hash2) 4.07E+002
1 . 2 hash_partial_groupby 4.07E+002
. . 1 trafodion_scan DMA_ENTTYPE_STAT 5.03E+006
--- SQL operation complete.
Best regards
Yuan
From: Liu, Yuan (Yuan) <yu...@esgyn.cn>
Sent: Friday, November 09, 2018 8:56 AM
To: dev@trafodion.apache.org
Subject: What does (m) mean in esp_exchange
Hi Trafodioneers,
I get a query plan below, can anyone teach me what does the (m) mean in red box? Thanks ahead.
[cid:image001.png@01D47809.FED29780]
Best regards
Yuan