Support `--tidb-force-priority` in dumpling like mydumper

[pingcap]

Support `--tidb-force-priority` in dumpling like mydumper

[lichunzhu]

Besides, should we support an argument to allow users to set session variables during the export process?

[kennytm]

allowing arbitrary session variables sounds better. if we focus on priority, the question becomes why don't see also support SELECT HIGH_PRIORITY on MySQL.

[lichunzhu]

allowing arbitrary session variables sounds better. if we focus on priority, the question becomes why don't see also support SELECT HIGH_PRIORITY on MySQL.

I think we can also support that for MySQL 😃

[kennytm]

there is no SELECT LOW_PRIORITY for MySQL so it's basically useless 🙃

[lichunzhu]

there is no SELECT LOW_PRIORITY for MySQL so it's basically useless 🙃

Yes.. It seems that LOW_PRIORITY can only be used for insert and update 😿

[kennytm]

With #167 this can be supported with --params tidb_force_priority=LOW_PRIORITY, so closing.