canal adapter的esMapping pk问题

配置如下：

dataSourceKey: defaultDS destination: dbastatinfo groupId: g1 esMapping: _index: dbastatinfo _type: _doc pk: _id sql: "select a.iGId as _id, a.inip from processlistinfo a" commitBatch: 1000

这么写，能拿到解析的数据，但是不能写到ES中。

日志如下：

2019-04-19 14:46:41.961 [pool-4-thread-1] DEBUG c.a.otter.canal.client.adapter.es.service.ESSyncService - DML: {"data":[{"id":7571826,"iGId":"1111","inip":"xxxx","port":1111,"iRole":"slave","proid":5073476,"USER":"xxxx","HOST":"xxxx","DB":"xxxx","COMMAND":"Sleep","TIME":39,"STATE":"","INFO":"None","addTime":1555524615000,"addDate":1555516800000,"version":"20190418021001","note":""}],"database":"xxxx","destination":"dbastatinfo","es":1555524615000,"groupId":null,"isDdl":false,"old":null,"pkNames":["id"],"sql":"","table":"processlistinfo","ts":1555656400212,"type":"INSERT"}

如果使用：

dataSourceKey: defaultDS destination: dbastatinfo groupId: g1 esMapping: _index: dbastatinfo _type: _doc _id: _id sql: "select a.iGId as _id, a.inip from processlistinfo a" commitBatch: 1000

则可正常写入。

求问：ES自动分配_id时，pk的配置应该怎么写？

原提问者GitHub用户Mysia