Can't analyze columns with string longer than 65535 bytes

[time-and-fate]

Bug Report

1. Minimal reproduce step (Required)

create table t(a longtext);
insert into t value(repeat("a",65535));
analyze table t with 0 topn;
insert into t value(repeat("a",65536));
analyze table t with 0 topn;

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

Analyze successfully.

3. What did you see instead (Required)

The second analyze failed.

ERROR 1406 (22001): Data too long for column 'lower_bound' at row 1

4. What is your TiDB version? (Required)

master

[winoros]

This bug affects the old statistics also.
Increasing the sample size just increases the possibility the bug occurs.

[time-and-fate]

This bug affects the old statistics also. Increasing the sample size just increases the possibility the bug occurs.

The old one has this PR. #7931 😂
You can try the example in the description with analyze_version set to 1. It can run successfully.

[github-actions]

Please check whether the issue should be labeled with 'affects-x.y' or 'fixes-x.y.z', and then remove 'needs-more-info' label.