Unit test TestAutoUpdate failed in 4.0 branch when new collation is enabled.

[bb7133]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

Enable the new collation by changing the code in

func init() {
        newCollationEnabled = 1  // always enable the new collation

	newCollatorMap = make(map[string]Collator)
        ...

And then run the test TestAutoUpdate:

bash$ cd $TIDB_SRC/statistics/handle
bash$ go test -check.f TestAutoUpdate

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

The test case ran successfully.

3. What did you see instead (Required)

FAIL: update_test.go:371: testStatsSuite.TestAutoUpdate

update_test.go:464:
    c.Assert(hg.NDV, Equals, int64(3))
... obtained int64 = 1
... expected int64 = 3

4. What is your TiDB version? (Required)

The commit hash is 3b2c7e763a3a918c5247fb2ac7cf551cb0460679 in release-4.0.

This issue is not reproduced in master branch.

[bb7133]

@winoros PTAL

[yudongusa]

@bb7133 @winoros should we close this issue if it no more exists?