Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

1. Create 100M table using sysbench.
2. Add index for the column c(char(120)).
3. The memory consumption keep increasing.

2. What did you expect to see? (Required)

It should be less than 8GB.

3. What did you see instead (Required)

The memory consumption increases to more than 15GB.

4. What is your TiDB version? (Required)

d2ace99