--访问表T用到了并行， 操作粒度为block，而M依旧是串行访问，第6步出现了S->P，并且是通过广播的方式向并行进程发送信息；
为表T开启并行alter table m parallel 4;
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| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | TQ |IN-OUT| PQ Distrib |
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| 0 | SELECT STATEMENT | | 23213 | 770K| 17 (6)| 00:00:01 | | | |
| 1 | PX COORDINATOR | | | | | | | | |
| 2 | PX SEND QC (RANDOM) | :TQ10001 | 23213 | 770K| 17 (6)| 00:00:01 | Q1,01 | P->S | QC (RAND) |
|* 3 | HASH JOIN | | 23213 | 770K| 17 (6)| 00:00:01 | Q1,01 | PCWP | |
| 4 | PX RECEIVE | | 1 | 4 | 2 (0)| 00:00:01 | Q1,01 | PCWP | |
| 5 | PX SEND BROADCAST | :TQ10000 | 1 | 4 | 2 (0)| 00:00:01 | Q1,00 | P->P | BROADCAST |
| 6 | PX BLOCK ITERATOR | | 1 | 4 | 2 (0)| 00:00:01 | Q1,00 | PCWC | |
|* 7 | TABLE ACCESS FULL| M | 1 | 4 | 2 (0)| 00:00:01 | Q1,00 | PCWP | |
| 8 | PX BLOCK ITERATOR | | 23213 | 680K| 14 (0)| 00:00:01 | Q1,01 | PCWC | |
|* 9 | TABLE ACCESS FULL | T | 23213 | 680K| 14 (0)| 00:00:01 | Q1,01 | PCWP | |
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--此时M也使用并行访问，操作粒度为block；因为sql没有要求排序，最后向coordinator使用RAND方式发送数据
--M的结果集使用广播的方式发送数据，使用hint /*+ pq_distribute(t,hash,hash) */可以将其改为Hash
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| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | TQ |IN-OUT| PQ Distrib |
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| 0 | SELECT STATEMENT | | 23213 | 770K| 17 (6)| 00:00:01 | | | |
| 1 | PX COORDINATOR | | | | | | | | |
| 2 | PX SEND QC (RANDOM) | :TQ10002 | 23213 | 770K| 17 (6)| 00:00:01 | Q1,02 | P->S | QC (RAND) |
|* 3 | HASH JOIN BUFFERED | | 23213 | 770K| 17 (6)| 00:00:01 | Q1,02 | PCWP | |
| 4 | PX RECEIVE | | 1 | 4 | 2 (0)| 00:00:01 | Q1,02 | PCWP | |
| 5 | PX SEND HASH | :TQ10000 | 1 | 4 | 2 (0)| 00:00:01 | Q1,00 | P->P | HASH |
| 6 | PX BLOCK ITERATOR | | 1 | 4 | 2 (0)| 00:00:01 | Q1,00 | PCWC | |
|* 7 | TABLE ACCESS FULL| M | 1 | 4 | 2 (0)| 00:00:01 | Q1,00 | PCWP | |
| 8 | PX RECEIVE | | 23213 | 680K| 14 (0)| 00:00:01 | Q1,02 | PCWP | |
| 9 | PX SEND HASH | :TQ10001 | 23213 | 680K| 14 (0)| 00:00:01 | Q1,01 | P->P | HASH |
| 10 | PX BLOCK ITERATOR | | 23213 | 680K| 14 (0)| 00:00:01 | Q1,01 | PCWC | |
|* 11 | TABLE ACCE