sorter iterator can utilize too much CPU if there are lots of DeleteRange records

[hicqu]

What did you do?

Start a TiCDC changefeed to replicate 4K tables. And there are a lot exists data.

What did you expect to see?

No response

What did you see instead?

Sorter iterators can utilize too much CPU if there are lots of DeleteRange records:

Versions of the cluster

Upstream TiDB cluster version (execute SELECT tidb_version(); in a MySQL client):

(paste TiDB cluster version here)

Upstream TiKV version (execute tikv-server --version):

(paste TiKV version here)

TiCDC version (execute cdc version):

(paste TiCDC version here)