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Posted to commits@doris.apache.org by GitBox <gi...@apache.org> on 2020/08/28 10:30:56 UTC

[GitHub] [incubator-doris] liutang123 opened a new issue #4481: Do not add exchange when table's distributioin satisfy the distribution requirements

liutang123 opened a new issue #4481:
URL: https://github.com/apache/incubator-doris/issues/4481


   issue Reason
   --
   Now, Doris will create two fragments for aggretion.
   Sometime, **Exchange for aggregation is unnecessary.**
   Think about follow cases:
   1. aggregate an unpartitioned table.
   a. create table SQL:
   ```
   CREATE TABLE `llj_test_1` (
     `dt` int(11) NOT NULL COMMENT "",
     `dis_key` varchar(20) NOT NULL COMMENT ""
   ) ENGINE=OLAP
   DUPLICATE KEY(`dt`, `dis_key`)
   COMMENT "OLAP"
   DISTRIBUTED BY HASH(`dt`, `dis_key`) BUCKETS 3
   PROPERTIES (
   "replication_num" = "3",
   "in_memory" = "false",
   "storage_format" = "DEFAULT"
   );
   ```
   b. query SQL:`select dt, dis_key,count(1) from  llj_test_1  group by dt, dis_key;`
   
   2. aggregate a partitioned table:
   a. create table SQL:
   ```
   CREATE TABLE `llj_test` (
     `dt` int(11) NOT NULL COMMENT "",
     `dis_key` varchar(20) NOT NULL COMMENT ""
   ) ENGINE=OLAP
   DUPLICATE KEY(`dt`, `dis_key`)
   COMMENT "OLAP"
   PARTITION BY RANGE(`dt`)
   (PARTITION p20180822 VALUES [("19000101"), ("20181021")),
   PARTITION p20181207 VALUES [("20181021"), ("20181022")))
   DISTRIBUTED BY HASH(`dt`, `dis_key`) BUCKETS 3
   PROPERTIES (
   "replication_num" = "1",
   "in_memory" = "false",
   "storage_format" = "DEFAULT"
   );
   ```
   b. query SQL:`select dt, dis_key,count(1) from  llj_test  group by dt, dis_key;`
   
   Suggestion
   --
   In `DistributedPlanner`, do not add the unnecessary `Exchange`s.
   


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[GitHub] [incubator-doris] liutang123 closed issue #4481: Do not add exchange when table's distributioin satisfy the distribution requirements

Posted by GitBox <gi...@apache.org>.
liutang123 closed issue #4481:
URL: https://github.com/apache/incubator-doris/issues/4481


   


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