'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) <[email protected]> Sent: Thursday, November 8, 2018 4:58 PM To: [email protected] 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) <[email protected]> Sent: Friday, November 09, 2018 8:56 AM To: [email protected] 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:[email protected]] Best regards Yuan
