一、gcluster_select_parallel_degree参数取值范围：[1-160]，默认值为1，不开启并发任务。当参数大于1时，视为开启并发查询任务。
该参数支持 session级别、global级别、配置文件级别。
二、并发查询任务数的计算方法：
1、set global gcluster_select_parallel_degree=5;
2、warehouse的Data节点数为2节点。
总并发数=data节点数*多分片并发查询参数=10
通过集群层express日志可以看出并发查询的个数与taskid相关，taskid从0开始计算。
2023-06-14 09:53:23.311 [SQLDISP][INFO ][S:2394][Q:259]<ExecSQL|2562>:instance: lxj1, txid: 16394234062568423430, minTxid: 16394234062568423430, queryid: 259, taskid: 6, addr: 10.10.9.19, type: 3
----sql: SELECT COUNT(1) FROM `vc00001_db1`.`customer` `sysvc.db1.customer`
----warehouse: 0x6785ee0
----table meta info:
table pfile list:
2023-06-14 09:53:23.311 [SQLDISP][INFO ][S:2394][Q:259]<ExecSQL|2562>:instance: lxj1, txid: 16394234062568423430, minTxid: 16394234062568423430, queryid: 259, taskid: 5, addr: 10.10.9.19, type: 3
----sql: SELECT COUNT(1) FROM `vc00001_db1`.`customer` `sysvc.db1.customer`
----warehouse: 0x6785ee0
----table meta info:
table pfile list:
2023-06-14 09:53:23.311 [SQLDISP][INFO ][S:2394][Q:259]<ExecSQL|2562>:instance: lxj1, txid: 16394234062568423430, minTxid: 16394234062568423430, queryid: 259, taskid: 4, addr: 10.10.6.130, type: 3
----sql: SELECT COUNT(1) FROM `vc00001_db1`.`customer` `sysvc.db1.customer`
----warehouse: 0x6785ee0
----table meta info:
table pfile list:
2023-06-14 09:53:23.311 [SQLDISP][INFO ][S:2394][Q:259]<ExecSQL|2562>:instance: lxj1, txid: 16394234062568423430, minTxid: 16394234062568423430, queryid: 259, taskid: 8, addr: 10.10.9.19, type: 3
----sql: SELECT COUNT(1) FROM `vc00001_db1`.`customer` `sysvc.db1.customer`
----warehouse: 0x6785ee0
----table meta info:
table pfile list:
2023-06-14 09:53:23.312 [SQLDISP][INFO ][S:2394][Q:259]<ExecSQL|2562>:instance: lxj1, txid: 16394234062568423430, minTxid: 16394234062568423430, queryid: 259, taskid: 0, addr: 10.10.6.130, type: 3
----sql: SELECT COUNT(1) FROM `vc00001_db1`.`customer` `sysvc.db1.customer`
----warehouse: 0x6785ee0
----table meta info:
table pfile list:
2023-06-14 09:53:23.312 [SQLDISP][INFO ][S:2394][Q:259]<ExecSQL|2562>:instance: lxj1, txid: 16394234062568423430, minTxid: 16394234062568423430, queryid: 259, taskid: 1, addr: 10.10.6.130, type: 3
----sql: SELECT COUNT(1) FROM `vc00001_db1`.`customer` `sysvc.db1.customer`
----warehouse: 0x6785ee0
----table meta info:
table pfile list:
2023-06-14 09:53:23.312 [SQLDISP][INFO ][S:2394][Q:259]<ExecSQL|2562>:instance: lxj1, txid: 16394234062568423430, minTxid: 16394234062568423430, queryid: 259, taskid: 9, addr: 10.10.9.19, type: 3
----sql: SELECT COUNT(1) FROM `vc00001_db1`.`customer` `sysvc.db1.customer`
----warehouse: 0x6785ee0
----table meta info:
table pfile list:
2023-06-14 09:53:23.312 [SQLDISP][INFO ][S:2394][Q:259]<ExecSQL|2562>:instance: lxj1, txid: 16394234062568423430, minTxid: 16394234062568423430, queryid: 259, taskid: 7, addr: 10.10.9.19, type: 3
----sql: SELECT COUNT(1) FROM `vc00001_db1`.`customer` `sysvc.db1.customer`
----warehouse: 0x6785ee0
----table meta info:
table pfile list:
2023-06-14 09:53:23.312 [SQLDISP][INFO ][S:2394][Q:259]<ExecSQL|2562>:instance: lxj1, txid: 16394234062568423430, minTxid: 16394234062568423430, queryid: 259, taskid: 3, addr: 10.10.6.130, type: 3
----sql: SELECT COUNT(1) FROM `vc00001_db1`.`customer` `sysvc.db1.customer`
----warehouse: 0x6785ee0
----table meta info:
table pfile list:
2023-06-14 09:53:23.314 [SQLDISP][INFO ][S:2394][Q:259]<ExecSQL|2562>:instance: lxj1, txid: 16394234062568423430, minTxid: 16394234062568423430, queryid: 259, taskid: 2, addr: 10.10.6.130, type: 3
----sql: SELECT COUNT(1) FROM `vc00001_db1`.`customer` `sysvc.db1.customer`
----warehouse: 0x6785ee0
----table meta info:
table pfile list:
